[PATCH v3 0/2] Add Apple Silicon SMC power driver

[PATCH v3 0/2] Add Apple Silicon SMC power driver

[Michael Reeves via B4 Relay]

This series adds a power supply driver for the Apple SMC found on
Apple Silicon devices. This allows the kernel to report AC status,
battery charging status, and power metrics, and modify the charging
behaviour.

The first patch adds the driver itself, and the second patch wires it
up to the MFD core.

The driver is based on an original out-of-tree implementation by
Hector Martin. It has been refactored for upstream inclusion, 
including support for newer SMC firmwares, devices without batteries,
dynamic property detection and improved state management.

Tested on: Apple M3 (MacBook Air, J613)

Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
---
Changes in v3:
- Rebase on top of latest linux-next
- Drop charge control threshold properties.
- Switch to devm_work_autocancel() for critical work.
- Add platform ID table and remove MODULE_ALIAS.
- Simplify property array management in struct macsmc_power.
- Improve probe error handling and device pointer usage.
- Minor style and indentation fixes.
- Link to v2: https://lore.kernel.org/r/20260109-b4-macsmc-power-v2-0-93818f1e7d62@gmail.com

Changes in v2:
- Added Reviewed-by: Neal Gompa <neal@gompa.dev> to all patches.
- Fixed Makefile alignment by using tabs for the macsmc-power entry.
- Upgraded physical battery exhaustion log level to EMERG.
- Downgraded software-triggered orderly poweroff log level to CRIT.
- Added check for CHIS key to skip AC registration on desktop models.
- Link to v1: https://lore.kernel.org/r/20260105-b4-macsmc-power-v1-0-62954c42a555@gmail.com

---
Michael Reeves (2):
      power: supply: Add macsmc-power driver for Apple Silicon
      mfd: macsmc: Wire up Apple SMC power driver

 MAINTAINERS                         |   1 +
 drivers/mfd/macsmc.c                |   1 +
 drivers/power/supply/Kconfig        |  11 +
 drivers/power/supply/Makefile       |   1 +
 drivers/power/supply/macsmc-power.c | 834 ++++++++++++++++++++++++++++++++++++
 5 files changed, 848 insertions(+)
---
base-commit: b775e489bec70895b7ef6b66927886bbac79598f
change-id: 20260105-b4-macsmc-power-d017cc7f53ac

Best regards,
-- 
Michael Reeves <michael.reeves077@gmail.com>

[PATCH v3 1/2] power: supply: Add macsmc-power driver for Apple Silicon

[Michael Reeves via B4 Relay]

From: Michael Reeves <michael.reeves077@gmail.com>

This driver provides battery and AC status monitoring for Apple Silicon
Macs via the SMC (System Management Controller). It supports
reporting capacity, voltage, current, and charging status.

Co-developed-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
---
 MAINTAINERS                         |   1 +
 drivers/power/supply/Kconfig        |  11 +
 drivers/power/supply/Makefile       |   1 +
 drivers/power/supply/macsmc-power.c | 834 ++++++++++++++++++++++++++++++++++++
 4 files changed, 847 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 6c7bd06dec7c..f776996121c9 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2513,6 +2513,7 @@ F:	drivers/nvmem/apple-spmi-nvmem.c
 F:	drivers/phy/apple/
 F:	drivers/pinctrl/pinctrl-apple-gpio.c
 F:	drivers/power/reset/macsmc-reboot.c
+F:	drivers/power/supply/macsmc-power.c
 F:	drivers/pwm/pwm-apple.c
 F:	drivers/rtc/rtc-macsmc.c
 F:	drivers/soc/apple/*
diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
index 92f9f7aae92f..3a5b7d9234c2 100644
--- a/drivers/power/supply/Kconfig
+++ b/drivers/power/supply/Kconfig
@@ -1132,4 +1132,15 @@ config FUEL_GAUGE_MM8013
 	  the state of charge, temperature, cycle count, actual and design
 	  capacity, etc.
 
+config MACSMC_POWER
+	tristate "Apple SMC Battery and Power Driver"
+	depends on MFD_MACSMC
+	help
+	  This driver provides support for the battery and AC adapter on
+	  Apple Silicon machines. It exposes battery telemetry (voltage,
+	  current, health) and AC adapter status through the standard Linux
+	  power supply framework.
+
+	  Say Y or M here if you have an Apple Silicon based Mac.
+
 endif # POWER_SUPPLY
diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
index 4b79d5abc49a..d14420b606d8 100644
--- a/drivers/power/supply/Makefile
+++ b/drivers/power/supply/Makefile
@@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
 obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
 obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_smbx.o
 obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o
+obj-$(CONFIG_MACSMC_POWER)	+= macsmc-power.o
diff --git a/drivers/power/supply/macsmc-power.c b/drivers/power/supply/macsmc-power.c
new file mode 100644
index 000000000000..9b3faefe7a45
--- /dev/null
+++ b/drivers/power/supply/macsmc-power.c
@@ -0,0 +1,834 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SMC Power/Battery Management Driver
+ *
+ * This driver exposes battery telemetry (voltage, current, temperature, health)
+ * and AC adapter status provided by the Apple SMC (System Management Controller)
+ * on Apple Silicon systems.
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <linux/ctype.h>
+#include <linux/delay.h>
+#include <linux/devm-helpers.h>
+#include <linux/limits.h>
+#include <linux/module.h>
+#include <linux/mfd/macsmc.h>
+#include <linux/notifier.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <linux/reboot.h>
+#include <linux/workqueue.h>
+
+#define MAX_STRING_LENGTH 256
+
+/*
+ * The SMC reports charge in mAh (Coulombs) but energy in mWh (Joules).
+ * We lack a register for "Nominal Voltage" or "Energy Accumulator".
+ * We use a fixed 3.8V/cell constant to approximate energy stats for userspace,
+ * derived from empirical data across supported MacBook models.
+ */
+#define MACSMC_NOMINAL_CELL_VOLTAGE_MV 3800
+
+/* SMC Key Flags */
+#define CHNC_BATTERY_FULL	BIT(0)
+#define CHNC_NO_CHARGER		BIT(7)
+#define CHNC_NOCHG_CH0C		BIT(14)
+#define CHNC_NOCHG_CH0B_CH0K	BIT(15)
+#define CHNC_BATTERY_FULL_2	BIT(18)
+#define CHNC_BMS_BUSY		BIT(23)
+#define CHNC_CHLS_LIMIT		BIT(24)
+#define CHNC_NOAC_CH0J		BIT(53)
+#define CHNC_NOAC_CH0I		BIT(54)
+
+#define CH0R_LOWER_FLAGS	GENMASK(15, 0)
+#define CH0R_NOAC_CH0I		BIT(0)
+#define CH0R_NOAC_DISCONNECTED	BIT(4)
+#define CH0R_NOAC_CH0J		BIT(5)
+#define CH0R_BMS_BUSY		BIT(8)
+#define CH0R_NOAC_CH0K		BIT(9)
+#define CH0R_NOAC_CHWA		BIT(11)
+
+#define CH0X_CH0C		BIT(0)
+#define CH0X_CH0B		BIT(1)
+
+#define ACSt_CAN_BOOT_AP	BIT(2)
+#define ACSt_CAN_BOOT_IBOOT	BIT(1)
+
+#define CHWA_CHLS_FIXED_START_OFFSET	5
+#define CHLS_MIN_END_THRESHOLD		10
+#define CHLS_FORCE_DISCHARGE		0x100
+#define CHWA_FIXED_END_THRESHOLD	80
+#define CHWA_PROP_WRITE_THRESHOLD	95
+
+#define MACSMC_MAX_BATT_PROPS		50
+#define MACSMC_MAX_AC_PROPS		10
+
+struct macsmc_power {
+	struct device *dev;
+	struct apple_smc *smc;
+
+	struct power_supply_desc ac_desc;
+	struct power_supply_desc batt_desc;
+
+	struct power_supply *batt;
+	struct power_supply *ac;
+
+	char model_name[MAX_STRING_LENGTH];
+	char serial_number[MAX_STRING_LENGTH];
+	char mfg_date[MAX_STRING_LENGTH];
+
+	bool has_chwa;
+	bool has_chls;
+	bool has_ch0i;
+	bool has_ch0c;
+	bool has_chte;
+
+	u8 num_cells;
+	int nominal_voltage_mv;
+
+	struct notifier_block nb;
+	struct work_struct critical_work;
+	bool shutdown_started;
+};
+
+static int macsmc_battery_get_status(struct macsmc_power *power)
+{
+	u64 nocharge_flags;
+	u32 nopower_flags;
+	u16 ac_current;
+	int charge_limit = 0;
+	bool limited = false;
+	bool flag;
+	int ret;
+
+	/*
+	 * Fallbacks exist for keys that may disappear in future hardware.
+	 * CHCE/CHCC/BSFC/CHSC are considered fundamental; absence is an error.
+	 */
+
+	/* Check if power input is inhibited (e.g. BMS balancing cycle) */
+	ret = apple_smc_read_u32(power->smc, SMC_KEY(CH0R), &nopower_flags);
+	if (!ret && (nopower_flags & CH0R_LOWER_FLAGS & ~CH0R_BMS_BUSY))
+		return POWER_SUPPLY_STATUS_DISCHARGING;
+
+	/* Check if charger is present */
+	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHCE), &flag);
+	if (ret < 0)
+		return ret;
+	if (!flag)
+		return POWER_SUPPLY_STATUS_DISCHARGING;
+
+	/* Check if AC is charge capable */
+	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHCC), &flag);
+	if (ret < 0)
+		return ret;
+	if (!flag)
+		return POWER_SUPPLY_STATUS_DISCHARGING;
+
+	/* Check if AC input limit is too low */
+	ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-i), &ac_current);
+	if (!ret && ac_current < 100)
+		return POWER_SUPPLY_STATUS_DISCHARGING;
+
+	/* Check if battery is full */
+	ret = apple_smc_read_flag(power->smc, SMC_KEY(BSFC), &flag);
+	if (ret < 0)
+		return ret;
+	if (flag)
+		return POWER_SUPPLY_STATUS_FULL;
+
+	/* Check for user-defined charge limits */
+	if (power->has_chls) {
+		u16 vu16;
+
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(CHLS), &vu16);
+		if (ret == 0 && (vu16 & 0xff) >= CHLS_MIN_END_THRESHOLD)
+			charge_limit = (vu16 & 0xff) - CHWA_CHLS_FIXED_START_OFFSET;
+	} else if (power->has_chwa) {
+		ret = apple_smc_read_flag(power->smc, SMC_KEY(CHWA), &flag);
+		if (ret == 0 && flag)
+			charge_limit = CHWA_FIXED_END_THRESHOLD - CHWA_CHLS_FIXED_START_OFFSET;
+	}
+
+	if (charge_limit > 0) {
+		u8 buic = 0;
+
+		if (apple_smc_read_u8(power->smc, SMC_KEY(BUIC), &buic) >= 0 &&
+		    buic >= charge_limit)
+			limited = true;
+	}
+
+	/* Check charging inhibitors */
+	ret = apple_smc_read_u64(power->smc, SMC_KEY(CHNC), &nocharge_flags);
+	if (!ret) {
+		if (nocharge_flags & CHNC_BATTERY_FULL)
+			return POWER_SUPPLY_STATUS_FULL;
+		/* BMS busy shows up as inhibit, but we treat it as charging */
+		else if (nocharge_flags == CHNC_BMS_BUSY && !limited)
+			return POWER_SUPPLY_STATUS_CHARGING;
+		else if (nocharge_flags)
+			return POWER_SUPPLY_STATUS_NOT_CHARGING;
+		else
+			return POWER_SUPPLY_STATUS_CHARGING;
+	}
+
+	/* Fallback: System charging flag */
+	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHSC), &flag);
+	if (ret < 0)
+		return ret;
+	if (!flag)
+		return POWER_SUPPLY_STATUS_NOT_CHARGING;
+
+	return POWER_SUPPLY_STATUS_CHARGING;
+}
+
+static int macsmc_battery_get_charge_behaviour(struct macsmc_power *power)
+{
+	int ret;
+	u8 val8;
+	u8 chte_buf[4];
+
+	if (power->has_ch0i) {
+		ret = apple_smc_read_u8(power->smc, SMC_KEY(CH0I), &val8);
+		if (ret)
+			return ret;
+		if (val8 & CH0R_NOAC_CH0I)
+			return POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE;
+	}
+
+	if (power->has_chte) {
+		ret = apple_smc_read(power->smc, SMC_KEY(CHTE), chte_buf, 4);
+		if (ret < 0)
+			return ret;
+
+		if (chte_buf[0] == 0x01)
+			return POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE;
+	} else if (power->has_ch0c) {
+		ret = apple_smc_read_u8(power->smc, SMC_KEY(CH0C), &val8);
+		if (ret)
+			return ret;
+		if (val8 & CH0X_CH0C)
+			return POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE;
+	}
+
+	return POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO;
+}
+
+static int macsmc_battery_set_charge_behaviour(struct macsmc_power *power, int val)
+{
+	int ret;
+
+	/* First, reset all inhibitors to a known-good 'auto' state */
+	if (power->has_ch0i) {
+		ret = apple_smc_write_u8(power->smc, SMC_KEY(CH0I), 0);
+		if (ret)
+			return ret;
+	}
+
+	if (power->has_chte) {
+		ret = apple_smc_write_u32(power->smc, SMC_KEY(CHTE), 0);
+		if (ret)
+			return ret;
+	} else if (power->has_ch0c) {
+		ret = apple_smc_write_u8(power->smc, SMC_KEY(CH0C), 0);
+		if (ret)
+			return ret;
+	}
+
+	switch (val) {
+	case POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO:
+		return 0;
+
+	case POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE:
+		if (power->has_chte)
+			return apple_smc_write_u32(power->smc, SMC_KEY(CHTE), 1);
+		else if (power->has_ch0c)
+			return apple_smc_write_u8(power->smc, SMC_KEY(CH0C), 1);
+		else
+			return -EOPNOTSUPP;
+		break;
+
+	case POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE:
+		if (!power->has_ch0i)
+			return -EOPNOTSUPP;
+		return apple_smc_write_u8(power->smc, SMC_KEY(CH0I), 1);
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int macsmc_battery_get_date(const char *s, int *out)
+{
+	if (!isdigit(s[0]) || !isdigit(s[1]))
+		return -EOPNOTSUPP;
+
+	*out = (s[0] - '0') * 10 + s[1] - '0';
+	return 0;
+}
+
+static int macsmc_battery_get_capacity_level(struct macsmc_power *power)
+{
+	bool flag;
+	u32 val;
+	int ret;
+
+	/* Check for emergency shutdown condition */
+	if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val) >= 0 && val)
+		return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
+
+	/* Check AC status for whether we could boot in this state */
+	if (apple_smc_read_u32(power->smc, SMC_KEY(ACSt), &val) >= 0) {
+		if (!(val & ACSt_CAN_BOOT_IBOOT))
+			return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
+
+		if (!(val & ACSt_CAN_BOOT_AP))
+			return POWER_SUPPLY_CAPACITY_LEVEL_LOW;
+	}
+
+	ret = apple_smc_read_flag(power->smc, SMC_KEY(BSFC), &flag);
+	if (ret < 0)
+		return POWER_SUPPLY_CAPACITY_LEVEL_UNKNOWN;
+
+	if (flag)
+		return POWER_SUPPLY_CAPACITY_LEVEL_FULL;
+	else
+		return POWER_SUPPLY_CAPACITY_LEVEL_NORMAL;
+}
+
+static int macsmc_battery_get_property(struct power_supply *psy,
+				       enum power_supply_property psp,
+				       union power_supply_propval *val)
+{
+	struct macsmc_power *power = power_supply_get_drvdata(psy);
+	int ret = 0;
+	u8 vu8;
+	u16 vu16;
+	s16 vs16;
+	s32 vs32;
+	s64 vs64;
+	bool flag;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_STATUS:
+		val->intval = macsmc_battery_get_status(power);
+		ret = val->intval < 0 ? val->intval : 0;
+		break;
+	case POWER_SUPPLY_PROP_PRESENT:
+		val->intval = 1;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
+		val->intval = macsmc_battery_get_charge_behaviour(power);
+		ret = val->intval < 0 ? val->intval : 0;
+		break;
+	case POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0TE), &vu16);
+		val->intval = vu16 == 0xffff ? 0 : vu16 * 60;
+		break;
+	case POWER_SUPPLY_PROP_TIME_TO_FULL_NOW:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0TF), &vu16);
+		val->intval = vu16 == 0xffff ? 0 : vu16 * 60;
+		break;
+	case POWER_SUPPLY_PROP_CAPACITY:
+		ret = apple_smc_read_u8(power->smc, SMC_KEY(BUIC), &vu8);
+		val->intval = vu8;
+		break;
+	case POWER_SUPPLY_PROP_CAPACITY_LEVEL:
+		val->intval = macsmc_battery_get_capacity_level(power);
+		ret = val->intval < 0 ? val->intval : 0;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CURRENT_NOW:
+		ret = apple_smc_read_s16(power->smc, SMC_KEY(B0AC), &vs16);
+		val->intval = vs16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_POWER_NOW:
+		ret = apple_smc_read_s32(power->smc, SMC_KEY(B0AP), &vs32);
+		val->intval = vs32 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(BITV), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
+		/* Calculate total max design voltage from per-cell maximum voltage */
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(BVVN), &vu16);
+		val->intval = vu16 * 1000 * power->num_cells;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MIN:
+		/* Lifetime min */
+		ret = apple_smc_read_s16(power->smc, SMC_KEY(BLPM), &vs16);
+		val->intval = vs16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MAX:
+		/* Lifetime max */
+		ret = apple_smc_read_s16(power->smc, SMC_KEY(BLPX), &vs16);
+		val->intval = vs16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RC), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT_MAX:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RI), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RV), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0DC), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_FULL:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0FC), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_NOW:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RM), &vu16);
+		/* B0RM is Big Endian, likely pass through from TI gas gauge */
+		val->intval = (s16)swab16(vu16) * 1000;
+		break;
+	case POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0DC), &vu16);
+		val->intval = vu16 * power->nominal_voltage_mv;
+		break;
+	case POWER_SUPPLY_PROP_ENERGY_FULL:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0FC), &vu16);
+		val->intval = vu16 * power->nominal_voltage_mv;
+		break;
+	case POWER_SUPPLY_PROP_ENERGY_NOW:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RM), &vu16);
+		/* B0RM is Big Endian, likely pass through from TI gas gauge */
+		val->intval = (s16)swab16(vu16) * power->nominal_voltage_mv;
+		break;
+	case POWER_SUPPLY_PROP_TEMP:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0AT), &vu16);
+		val->intval = vu16 - 2732; /* Kelvin x10 to Celsius x10 */
+		break;
+	case POWER_SUPPLY_PROP_CHARGE_COUNTER:
+		ret = apple_smc_read_s64(power->smc, SMC_KEY(BAAC), &vs64);
+		val->intval = vs64;
+		break;
+	case POWER_SUPPLY_PROP_CYCLE_COUNT:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0CT), &vu16);
+		val->intval = vu16;
+		break;
+	case POWER_SUPPLY_PROP_SCOPE:
+		val->intval = POWER_SUPPLY_SCOPE_SYSTEM;
+		break;
+	case POWER_SUPPLY_PROP_HEALTH:
+		flag = false;
+		ret = apple_smc_read_flag(power->smc, SMC_KEY(BBAD), &flag);
+		val->intval = flag ? POWER_SUPPLY_HEALTH_DEAD : POWER_SUPPLY_HEALTH_GOOD;
+		break;
+	case POWER_SUPPLY_PROP_MODEL_NAME:
+		val->strval = power->model_name;
+		break;
+	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
+		val->strval = power->serial_number;
+		break;
+	case POWER_SUPPLY_PROP_MANUFACTURE_YEAR:
+		ret = macsmc_battery_get_date(&power->mfg_date[0], &val->intval);
+		/* The SMC reports the manufacture year as an offset from 1992. */
+		val->intval += 1992;
+		break;
+	case POWER_SUPPLY_PROP_MANUFACTURE_MONTH:
+		ret = macsmc_battery_get_date(&power->mfg_date[2], &val->intval);
+		break;
+	case POWER_SUPPLY_PROP_MANUFACTURE_DAY:
+		ret = macsmc_battery_get_date(&power->mfg_date[4], &val->intval);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static int macsmc_battery_set_property(struct power_supply *psy,
+				       enum power_supply_property psp,
+				       const union power_supply_propval *val)
+{
+	struct macsmc_power *power = power_supply_get_drvdata(psy);
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
+		return macsmc_battery_set_charge_behaviour(power, val->intval);
+	default:
+		return -EINVAL;
+	}
+}
+
+static int macsmc_battery_property_is_writeable(struct power_supply *psy,
+						enum power_supply_property psp)
+{
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static const struct power_supply_desc macsmc_battery_desc_template = {
+	.name			= "macsmc-battery",
+	.type			= POWER_SUPPLY_TYPE_BATTERY,
+	.get_property		= macsmc_battery_get_property,
+	.set_property		= macsmc_battery_set_property,
+	.property_is_writeable	= macsmc_battery_property_is_writeable,
+};
+
+static int macsmc_ac_get_property(struct power_supply *psy,
+				  enum power_supply_property psp,
+				  union power_supply_propval *val)
+{
+	struct macsmc_power *power = power_supply_get_drvdata(psy);
+	int ret = 0;
+	u16 vu16;
+	u32 vu32;
+
+	switch (psp) {
+	case POWER_SUPPLY_PROP_ONLINE:
+		ret = apple_smc_read_u32(power->smc, SMC_KEY(CHIS), &vu32);
+		val->intval = !!vu32;
+		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-n), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
+		ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-i), &vu16);
+		val->intval = vu16 * 1000;
+		break;
+	case POWER_SUPPLY_PROP_INPUT_POWER_LIMIT:
+		ret = apple_smc_read_u32(power->smc, SMC_KEY(ACPW), &vu32);
+		val->intval = vu32 * 1000;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static const struct power_supply_desc macsmc_ac_desc_template = {
+	.name			= "macsmc-ac",
+	.type			= POWER_SUPPLY_TYPE_MAINS,
+	.get_property		= macsmc_ac_get_property,
+};
+
+static void macsmc_power_critical_work(struct work_struct *wrk)
+{
+	struct macsmc_power *power = container_of(wrk, struct macsmc_power, critical_work);
+	u16 bitv, b0av;
+	u32 bcf0;
+
+	if (!power->batt)
+		return;
+
+	/*
+	 * EMERGENCY: Check voltage vs design minimum.
+	 * If we are below BITV, the battery is physically exhausted.
+	 * We must shut down NOW to protect the filesystem.
+	 */
+	if (apple_smc_read_u16(power->smc, SMC_KEY(BITV), &bitv) >= 0 &&
+	    apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &b0av) >= 0 &&
+	    b0av < bitv) {
+		dev_emerg(power->dev,
+			  "Battery voltage (%d mV) below design minimum (%d mV)! Emergency shutdown.\n",
+			  b0av, bitv);
+		kernel_power_off();
+		return;
+	}
+
+	/*
+	 * Avoid duplicate attempts at orderly shutdown.
+	 * Voltage check is above this as we may want to
+	 * "upgrade" an orderly shutdown to a critical power
+	 * off if voltage drops.
+	 */
+	if (power->shutdown_started || system_state > SYSTEM_RUNNING)
+		return;
+
+	/*
+	 * Check if SMC flagged the battery as empty.
+	 * We trigger a graceful shutdown to let the OS save data.
+	 */
+	if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &bcf0) == 0 && bcf0 != 0) {
+		power->shutdown_started = true;
+		dev_crit(power->dev, "Battery critical (empty flag set). Triggering orderly shutdown.\n");
+		orderly_poweroff(true);
+	}
+}
+
+static int macsmc_power_event(struct notifier_block *nb, unsigned long event, void *data)
+{
+	struct macsmc_power *power = container_of(nb, struct macsmc_power, nb);
+
+	/*
+	 * SMC Event IDs are reverse-engineered.
+	 * 0x71... indicates power/battery events.
+	 */
+	if ((event & 0xffffff00) == 0x71010100 || /* Charger status change */
+	    (event & 0xffff0000) == 0x71060000 || /* Port charge state change */
+	    (event & 0xffff0000) == 0x71130000) { /* Connector insert/remove event */
+		if (power->batt)
+			power_supply_changed(power->batt);
+		if (power->ac)
+			power_supply_changed(power->ac);
+		return NOTIFY_OK;
+	} else if (event == 0x71020000) {
+		/* Critical battery warning */
+		if (power->batt)
+			schedule_work(&power->critical_work);
+		return NOTIFY_OK;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static int macsmc_power_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
+	struct power_supply_config psy_cfg = {};
+	struct macsmc_power *power;
+	bool has_battery = false;
+	bool has_ac_adapter = false;
+	int ret = -ENODEV;
+	bool flag;
+	u16 vu16;
+	u32 val32;
+	enum power_supply_property *props;
+	size_t nprops;
+
+	if (!smc)
+		return -ENODEV;
+
+	power = devm_kzalloc(dev, sizeof(*power), GFP_KERNEL);
+	if (!power)
+		return -ENOMEM;
+
+	power->dev = dev;
+	power->smc = smc;
+	dev_set_drvdata(dev, power);
+
+	INIT_WORK(&power->critical_work, macsmc_power_critical_work);
+	ret = devm_work_autocancel(dev, &power->critical_work, macsmc_power_critical_work);
+	if (ret)
+		return ret;
+
+	/*
+	 * Check for battery presence.
+	 * B0AV is a fundamental key.
+	 */
+	if (apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16) == 0 &&
+	    macsmc_battery_get_status(power) > POWER_SUPPLY_STATUS_UNKNOWN)
+		has_battery = true;
+
+	/*
+	 * Check for AC adapter presence.
+	 * CHIS is a fundamental key.
+	 */
+	if (apple_smc_key_exists(smc, SMC_KEY(CHIS)))
+		has_ac_adapter = true;
+
+	if (has_battery) {
+		power->batt_desc = macsmc_battery_desc_template;
+		props = devm_kcalloc(dev, MACSMC_MAX_BATT_PROPS,
+				     sizeof(enum power_supply_property),
+				     GFP_KERNEL);
+		if (!props)
+			return -ENOMEM;
+
+		nprops = 0;
+
+		/* Fundamental properties */
+		props[nprops++] = POWER_SUPPLY_PROP_STATUS;
+		props[nprops++] = POWER_SUPPLY_PROP_PRESENT;
+		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_NOW;
+		props[nprops++] = POWER_SUPPLY_PROP_CURRENT_NOW;
+		props[nprops++] = POWER_SUPPLY_PROP_POWER_NOW;
+		props[nprops++] = POWER_SUPPLY_PROP_CAPACITY;
+		props[nprops++] = POWER_SUPPLY_PROP_CAPACITY_LEVEL;
+		props[nprops++] = POWER_SUPPLY_PROP_TEMP;
+		props[nprops++] = POWER_SUPPLY_PROP_CYCLE_COUNT;
+		props[nprops++] = POWER_SUPPLY_PROP_HEALTH;
+		props[nprops++] = POWER_SUPPLY_PROP_SCOPE;
+		props[nprops++] = POWER_SUPPLY_PROP_MODEL_NAME;
+		props[nprops++] = POWER_SUPPLY_PROP_SERIAL_NUMBER;
+		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_YEAR;
+		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_MONTH;
+		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_DAY;
+
+		/* Extended properties usually present */
+		props[nprops++] = POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW;
+		props[nprops++] = POWER_SUPPLY_PROP_TIME_TO_FULL_NOW;
+		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN;
+		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN;
+		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MIN;
+		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MAX;
+		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT;
+		props[nprops++] = POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT_MAX;
+		props[nprops++] = POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE;
+		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN;
+		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_FULL;
+		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_NOW;
+		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN;
+		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_FULL;
+		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_NOW;
+		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_COUNTER;
+
+		/* Detect features based on key availability */
+		if (apple_smc_key_exists(smc, SMC_KEY(CHTE)))
+			power->has_chte = true;
+		if (apple_smc_key_exists(smc, SMC_KEY(CH0C)))
+			power->has_ch0c = true;
+		if (apple_smc_key_exists(smc, SMC_KEY(CH0I)))
+			power->has_ch0i = true;
+
+		/* Reset "Optimised Battery Charging" flags to default state */
+		if (power->has_chte)
+			apple_smc_write_u32(smc, SMC_KEY(CHTE), 0);
+		else if (power->has_ch0c)
+			apple_smc_write_u8(smc, SMC_KEY(CH0C), 0);
+
+		if (power->has_ch0i)
+			apple_smc_write_u8(smc, SMC_KEY(CH0I), 0);
+
+		apple_smc_write_u8(smc, SMC_KEY(CH0K), 0);
+		apple_smc_write_u8(smc, SMC_KEY(CH0B), 0);
+
+		/* Configure charge behaviour if supported */
+		if (power->has_ch0i || power->has_ch0c || power->has_chte) {
+			props[nprops++] = POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR;
+
+			power->batt_desc.charge_behaviours =
+				BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO);
+
+			if (power->has_ch0i)
+				power->batt_desc.charge_behaviours |=
+					BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE);
+
+			if (power->has_chte || power->has_ch0c)
+				power->batt_desc.charge_behaviours |=
+					BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE);
+		}
+
+		/* Detect charge limit method (CHWA vs CHLS) */
+		if (apple_smc_read_flag(power->smc, SMC_KEY(CHWA), &flag) == 0)
+			power->has_chwa = true;
+		else if (apple_smc_read_u16(power->smc, SMC_KEY(CHLS), &vu16) >= 0)
+			power->has_chls = true;
+
+		power->batt_desc.properties = props;
+		power->batt_desc.num_properties = nprops;
+
+		/* Fetch identity strings */
+		apple_smc_read(smc, SMC_KEY(BMDN), power->model_name,
+			       sizeof(power->model_name) - 1);
+		apple_smc_read(smc, SMC_KEY(BMSN), power->serial_number,
+			       sizeof(power->serial_number) - 1);
+		apple_smc_read(smc, SMC_KEY(BMDT), power->mfg_date,
+			       sizeof(power->mfg_date) - 1);
+
+		apple_smc_read_u8(power->smc, SMC_KEY(BNCB), &power->num_cells);
+		power->nominal_voltage_mv = MACSMC_NOMINAL_CELL_VOLTAGE_MV * power->num_cells;
+
+		/* Enable critical shutdown notifications by reading status once */
+		apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val32);
+
+		psy_cfg.drv_data = power;
+		power->batt = devm_power_supply_register(dev, &power->batt_desc, &psy_cfg);
+		if (IS_ERR(power->batt)) {
+			dev_err_probe(dev, PTR_ERR(power->batt),
+				      "Failed to register battery\n");
+			/* Don't return failure yet; try AC registration first */
+			power->batt = NULL;
+		}
+	} else {
+		dev_dbg(dev, "No battery detected.\n");
+	}
+
+	if (has_ac_adapter) {
+		power->ac_desc = macsmc_ac_desc_template;
+		props = devm_kcalloc(dev, MACSMC_MAX_AC_PROPS,
+				     sizeof(enum power_supply_property),
+				     GFP_KERNEL);
+		if (!props)
+			return -ENOMEM;
+
+		nprops = 0;
+
+		/* Online status is fundamental */
+		props[nprops++] = POWER_SUPPLY_PROP_ONLINE;
+
+		/* Input power limits are usually available */
+		if (apple_smc_key_exists(power->smc, SMC_KEY(ACPW)))
+			props[nprops++] = POWER_SUPPLY_PROP_INPUT_POWER_LIMIT;
+
+		/* macOS 15.4+ firmware dropped legacy AC keys (AC-n, AC-i) */
+		if (apple_smc_read_u16(power->smc, SMC_KEY(AC-n), &vu16) >= 0) {
+			props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_NOW;
+			props[nprops++] = POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT;
+		}
+
+		power->ac_desc.properties = props;
+		power->ac_desc.num_properties = nprops;
+
+		psy_cfg.drv_data = power;
+		power->ac = devm_power_supply_register(dev, &power->ac_desc, &psy_cfg);
+		if (IS_ERR(power->ac)) {
+			dev_err_probe(dev, PTR_ERR(power->ac),
+				      "Failed to register AC adapter\n");
+			power->ac = NULL;
+		}
+	} else {
+		dev_dbg(dev, "No A/C adapter detected.\n");
+	}
+
+	/* Final check: did we register anything? */
+	if (!power->batt && !power->ac)
+		return ret;
+
+	power->nb.notifier_call = macsmc_power_event;
+	blocking_notifier_chain_register(&smc->event_handlers, &power->nb);
+
+	return 0;
+}
+
+static void macsmc_power_remove(struct platform_device *pdev)
+{
+	struct macsmc_power *power = dev_get_drvdata(&pdev->dev);
+
+	blocking_notifier_chain_unregister(&power->smc->event_handlers, &power->nb);
+}
+
+static const struct platform_device_id macsmc_power_id[] = {
+	{ "macsmc-power" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, macsmc_power_id);
+
+static struct platform_driver macsmc_power_driver = {
+	.driver = {
+		.name = "macsmc-power",
+	},
+	.id_table = macsmc_power_id,
+	.probe = macsmc_power_probe,
+	.remove = macsmc_power_remove,
+};
+module_platform_driver(macsmc_power_driver);
+
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_DESCRIPTION("Apple SMC battery and power management driver");
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_AUTHOR("Michael Reeves <michael.reeves077@gmail.com>");

-- 
2.51.2

Re: [PATCH v3 1/2] power: supply: Add macsmc-power driver for Apple Silicon

[Sven Peter]

Hi,


On 1/15/26 08:08, Michael Reeves via B4 Relay wrote:
> From: Michael Reeves <michael.reeves077@gmail.com>
>
> This driver provides battery and AC status monitoring for Apple Silicon
> Macs via the SMC (System Management Controller). It supports
> reporting capacity, voltage, current, and charging status.
>
> Co-developed-by: Hector Martin <marcan@marcan.st>
> Signed-off-by: Hector Martin <marcan@marcan.st>
> Reviewed-by: Neal Gompa <neal@gompa.dev>
> Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
> ---
>   MAINTAINERS                         |   1 +
>   drivers/power/supply/Kconfig        |  11 +
>   drivers/power/supply/Makefile       |   1 +
>   drivers/power/supply/macsmc-power.c | 834 ++++++++++++++++++++++++++++++++++++
>   4 files changed, 847 insertions(+)
[...]
> +
> +static int macsmc_power_event(struct notifier_block *nb, unsigned long event, void *data)
> +{
> +	struct macsmc_power *power = container_of(nb, struct macsmc_power, nb);
> +
> +	/*
> +	 * SMC Event IDs are reverse-engineered.

Any chance you meant something else here? The event IDs aren't special, 
everything here is reverse-engineered ;)
No need to change this imho unless there's another reason for a v4 though:

Reviewed-by: Sven Peter <sven@kernel.org>


Sven

Re: [PATCH v3 1/2] power: supply: Add macsmc-power driver for Apple Silicon

[Michael Reeves]

Hi Sven,

Thank you so much for looking into this!

On Fri, Jan 16, 2026 at 8:00 AM Sven Peter <sven@kernel.org> wrote:
[...]
> > +
> > +static int macsmc_power_event(struct notifier_block *nb, unsigned long event, void *data)
> > +{
> > +     struct macsmc_power *power = container_of(nb, struct macsmc_power, nb);
> > +
> > +     /*
> > +      * SMC Event IDs are reverse-engineered.
>
> Any chance you meant something else here? The event IDs aren't special,
> everything here is reverse-engineered ;)
I was more meaning that they are made by correlating when certain
event IDs appear,
so the comments I've added aren't 100% certain as what Apple intended
for each ID,
(unlike keys where we can be more certain because they report a
physical value).
I guess that wasn't the best choice of words as everything is RE'ed,
as you've said.
In v4 I'll make this clearer, thank you for the pickup.

Best regards,
Michael

Re: [PATCH v3 1/2] power: supply: Add macsmc-power driver for Apple Silicon

[Janne Grunau]

On Thu, Jan 15, 2026 at 06:08:15PM +1100, Michael Reeves via B4 Relay wrote:
> From: Michael Reeves <michael.reeves077@gmail.com>

I think the driver is overall similar to the downstream AsahiLinux
driver so please keep Hector as author.

> This driver provides battery and AC status monitoring for Apple Silicon
> Macs via the SMC (System Management Controller). It supports
> reporting capacity, voltage, current, and charging status.
> 
> Co-developed-by: Hector Martin <marcan@marcan.st>
> Signed-off-by: Hector Martin <marcan@marcan.st>

The downstream driver a quite a few more Co-developed-by:/Sobs. When I
squashed the commits I decided to err on the safe side and included
commit authors from incremental patches as Co-developed-by: Why did you
drop those?

> Reviewed-by: Neal Gompa <neal@gompa.dev>
> Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
> ---
>  MAINTAINERS                         |   1 +
>  drivers/power/supply/Kconfig        |  11 +
>  drivers/power/supply/Makefile       |   1 +
>  drivers/power/supply/macsmc-power.c | 834 ++++++++++++++++++++++++++++++++++++
>  4 files changed, 847 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 6c7bd06dec7c..f776996121c9 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2513,6 +2513,7 @@ F:	drivers/nvmem/apple-spmi-nvmem.c
>  F:	drivers/phy/apple/
>  F:	drivers/pinctrl/pinctrl-apple-gpio.c
>  F:	drivers/power/reset/macsmc-reboot.c
> +F:	drivers/power/supply/macsmc-power.c
>  F:	drivers/pwm/pwm-apple.c
>  F:	drivers/rtc/rtc-macsmc.c
>  F:	drivers/soc/apple/*
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index 92f9f7aae92f..3a5b7d9234c2 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -1132,4 +1132,15 @@ config FUEL_GAUGE_MM8013
>  	  the state of charge, temperature, cycle count, actual and design
>  	  capacity, etc.
>  
> +config MACSMC_POWER
> +	tristate "Apple SMC Battery and Power Driver"
> +	depends on MFD_MACSMC
> +	help
> +	  This driver provides support for the battery and AC adapter on
> +	  Apple Silicon machines. It exposes battery telemetry (voltage,
> +	  current, health) and AC adapter status through the standard Linux
> +	  power supply framework.
> +
> +	  Say Y or M here if you have an Apple Silicon based Mac.
> +
>  endif # POWER_SUPPLY
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index 4b79d5abc49a..d14420b606d8 100644
> --- a/drivers/power/supply/Makefile
> +++ b/drivers/power/supply/Makefile
> @@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
>  obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
>  obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_smbx.o
>  obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o
> +obj-$(CONFIG_MACSMC_POWER)	+= macsmc-power.o
> diff --git a/drivers/power/supply/macsmc-power.c b/drivers/power/supply/macsmc-power.c
> new file mode 100644
> index 000000000000..9b3faefe7a45
> --- /dev/null
> +++ b/drivers/power/supply/macsmc-power.c
> @@ -0,0 +1,834 @@
> +// SPDX-License-Identifier: GPL-2.0-only OR MIT
> +/*
> + * Apple SMC Power/Battery Management Driver
> + *
> + * This driver exposes battery telemetry (voltage, current, temperature, health)
> + * and AC adapter status provided by the Apple SMC (System Management Controller)
> + * on Apple Silicon systems.
> + *
> + * Copyright The Asahi Linux Contributors
> + */
> +
> +#include <linux/ctype.h>
> +#include <linux/delay.h>
> +#include <linux/devm-helpers.h>
> +#include <linux/limits.h>
> +#include <linux/module.h>
> +#include <linux/mfd/macsmc.h>
> +#include <linux/notifier.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/power_supply.h>
> +#include <linux/reboot.h>
> +#include <linux/workqueue.h>
> +
> +#define MAX_STRING_LENGTH 256
> +
> +/*
> + * The SMC reports charge in mAh (Coulombs) but energy in mWh (Joules).
> + * We lack a register for "Nominal Voltage" or "Energy Accumulator".
> + * We use a fixed 3.8V/cell constant to approximate energy stats for userspace,
> + * derived from empirical data across supported MacBook models.
> + */
> +#define MACSMC_NOMINAL_CELL_VOLTAGE_MV 3800
> +
> +/* SMC Key Flags */
> +#define CHNC_BATTERY_FULL	BIT(0)
> +#define CHNC_NO_CHARGER		BIT(7)
> +#define CHNC_NOCHG_CH0C		BIT(14)
> +#define CHNC_NOCHG_CH0B_CH0K	BIT(15)
> +#define CHNC_BATTERY_FULL_2	BIT(18)
> +#define CHNC_BMS_BUSY		BIT(23)
> +#define CHNC_CHLS_LIMIT		BIT(24)
> +#define CHNC_NOAC_CH0J		BIT(53)
> +#define CHNC_NOAC_CH0I		BIT(54)
> +
> +#define CH0R_LOWER_FLAGS	GENMASK(15, 0)
> +#define CH0R_NOAC_CH0I		BIT(0)
> +#define CH0R_NOAC_DISCONNECTED	BIT(4)
> +#define CH0R_NOAC_CH0J		BIT(5)
> +#define CH0R_BMS_BUSY		BIT(8)
> +#define CH0R_NOAC_CH0K		BIT(9)
> +#define CH0R_NOAC_CHWA		BIT(11)
> +
> +#define CH0X_CH0C		BIT(0)
> +#define CH0X_CH0B		BIT(1)
> +
> +#define ACSt_CAN_BOOT_AP	BIT(2)
> +#define ACSt_CAN_BOOT_IBOOT	BIT(1)
> +
> +#define CHWA_CHLS_FIXED_START_OFFSET	5
> +#define CHLS_MIN_END_THRESHOLD		10
> +#define CHLS_FORCE_DISCHARGE		0x100
> +#define CHWA_FIXED_END_THRESHOLD	80
> +#define CHWA_PROP_WRITE_THRESHOLD	95
> +
> +#define MACSMC_MAX_BATT_PROPS		50
> +#define MACSMC_MAX_AC_PROPS		10
> +
> +struct macsmc_power {
> +	struct device *dev;
> +	struct apple_smc *smc;
> +
> +	struct power_supply_desc ac_desc;
> +	struct power_supply_desc batt_desc;
> +
> +	struct power_supply *batt;
> +	struct power_supply *ac;
> +
> +	char model_name[MAX_STRING_LENGTH];
> +	char serial_number[MAX_STRING_LENGTH];
> +	char mfg_date[MAX_STRING_LENGTH];
> +
> +	bool has_chwa;
> +	bool has_chls;
> +	bool has_ch0i;
> +	bool has_ch0c;
> +	bool has_chte;

I think comments what these keys do and in which firmware version the
appeared or vanished would be helpful here. I can Help with digging
through the history.

> +
> +	u8 num_cells;
> +	int nominal_voltage_mv;
> +
> +	struct notifier_block nb;
> +	struct work_struct critical_work;
> +	bool shutdown_started;
> +};
> +
> +static int macsmc_battery_get_status(struct macsmc_power *power)
> +{
> +	u64 nocharge_flags;
> +	u32 nopower_flags;
> +	u16 ac_current;
> +	int charge_limit = 0;
> +	bool limited = false;
> +	bool flag;
> +	int ret;
> +
> +	/*
> +	 * Fallbacks exist for keys that may disappear in future hardware.
> +	 * CHCE/CHCC/BSFC/CHSC are considered fundamental; absence is an error.
> +	 */

Why did you rewrite this (and many other) comments? I don't think this
is an improvement over the comment in the downstream driver.

> +	/* Check if power input is inhibited (e.g. BMS balancing cycle) */
> +	ret = apple_smc_read_u32(power->smc, SMC_KEY(CH0R), &nopower_flags);
> +	if (!ret && (nopower_flags & CH0R_LOWER_FLAGS & ~CH0R_BMS_BUSY))
> +		return POWER_SUPPLY_STATUS_DISCHARGING;
> +
> +	/* Check if charger is present */
> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHCE), &flag);
> +	if (ret < 0)
> +		return ret;
> +	if (!flag)
> +		return POWER_SUPPLY_STATUS_DISCHARGING;
> +
> +	/* Check if AC is charge capable */
> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHCC), &flag);
> +	if (ret < 0)
> +		return ret;
> +	if (!flag)
> +		return POWER_SUPPLY_STATUS_DISCHARGING;
> +
> +	/* Check if AC input limit is too low */
> +	ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-i), &ac_current);
> +	if (!ret && ac_current < 100)
> +		return POWER_SUPPLY_STATUS_DISCHARGING;
> +
> +	/* Check if battery is full */
> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(BSFC), &flag);
> +	if (ret < 0)
> +		return ret;
> +	if (flag)
> +		return POWER_SUPPLY_STATUS_FULL;
> +
> +	/* Check for user-defined charge limits */
> +	if (power->has_chls) {
> +		u16 vu16;
> +
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(CHLS), &vu16);
> +		if (ret == 0 && (vu16 & 0xff) >= CHLS_MIN_END_THRESHOLD)
> +			charge_limit = (vu16 & 0xff) - CHWA_CHLS_FIXED_START_OFFSET;
> +	} else if (power->has_chwa) {
> +		ret = apple_smc_read_flag(power->smc, SMC_KEY(CHWA), &flag);
> +		if (ret == 0 && flag)
> +			charge_limit = CHWA_FIXED_END_THRESHOLD - CHWA_CHLS_FIXED_START_OFFSET;
> +	}
> +
> +	if (charge_limit > 0) {
> +		u8 buic = 0;
> +
> +		if (apple_smc_read_u8(power->smc, SMC_KEY(BUIC), &buic) >= 0 &&
> +		    buic >= charge_limit)
> +			limited = true;
> +	}
> +
> +	/* Check charging inhibitors */
> +	ret = apple_smc_read_u64(power->smc, SMC_KEY(CHNC), &nocharge_flags);
> +	if (!ret) {
> +		if (nocharge_flags & CHNC_BATTERY_FULL)
> +			return POWER_SUPPLY_STATUS_FULL;
> +		/* BMS busy shows up as inhibit, but we treat it as charging */
> +		else if (nocharge_flags == CHNC_BMS_BUSY && !limited)
> +			return POWER_SUPPLY_STATUS_CHARGING;
> +		else if (nocharge_flags)
> +			return POWER_SUPPLY_STATUS_NOT_CHARGING;
> +		else
> +			return POWER_SUPPLY_STATUS_CHARGING;
> +	}
> +
> +	/* Fallback: System charging flag */
> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHSC), &flag);
> +	if (ret < 0)
> +		return ret;
> +	if (!flag)
> +		return POWER_SUPPLY_STATUS_NOT_CHARGING;
> +
> +	return POWER_SUPPLY_STATUS_CHARGING;
> +}
> +
> +static int macsmc_battery_get_charge_behaviour(struct macsmc_power *power)
> +{
> +	int ret;
> +	u8 val8;
> +	u8 chte_buf[4];
> +
> +	if (power->has_ch0i) {
> +		ret = apple_smc_read_u8(power->smc, SMC_KEY(CH0I), &val8);
> +		if (ret)
> +			return ret;
> +		if (val8 & CH0R_NOAC_CH0I)
> +			return POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE;
> +	}
> +
> +	if (power->has_chte) {
> +		ret = apple_smc_read(power->smc, SMC_KEY(CHTE), chte_buf, 4);
> +		if (ret < 0)
> +			return ret;
> +
> +		if (chte_buf[0] == 0x01)
> +			return POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE;
> +	} else if (power->has_ch0c) {
> +		ret = apple_smc_read_u8(power->smc, SMC_KEY(CH0C), &val8);
> +		if (ret)
> +			return ret;
> +		if (val8 & CH0X_CH0C)
> +			return POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE;
> +	}
> +
> +	return POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO;
> +}
> +
> +static int macsmc_battery_set_charge_behaviour(struct macsmc_power *power, int val)
> +{
> +	int ret;
> +
> +	/* First, reset all inhibitors to a known-good 'auto' state */

why? I wouldn't expect this function to make any if `val` is not
supported. If has_ch0i is not true
POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE will reset inhibit charge
and return -EOPNOTSUPP which is unexpected.
Resetting the values first and then change them to the actual desired
values doesn't make much sense either.
Yes, it's a little annoying to make the same calls in multiple cases of
the switch statement but you could move the `power->has_*` checks and
the smc writes to a single line.

> +	if (power->has_ch0i) {
> +		ret = apple_smc_write_u8(power->smc, SMC_KEY(CH0I), 0);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (power->has_chte) {
> +		ret = apple_smc_write_u32(power->smc, SMC_KEY(CHTE), 0);
> +		if (ret)
> +			return ret;
> +	} else if (power->has_ch0c) {
> +		ret = apple_smc_write_u8(power->smc, SMC_KEY(CH0C), 0);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	switch (val) {
> +	case POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO:
> +		return 0;
> +
> +	case POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE:
> +		if (power->has_chte)
> +			return apple_smc_write_u32(power->smc, SMC_KEY(CHTE), 1);
> +		else if (power->has_ch0c)
> +			return apple_smc_write_u8(power->smc, SMC_KEY(CH0C), 1);
> +		else
> +			return -EOPNOTSUPP;
> +		break;
> +
> +	case POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE:
> +		if (!power->has_ch0i)
> +			return -EOPNOTSUPP;
> +		return apple_smc_write_u8(power->smc, SMC_KEY(CH0I), 1);
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int macsmc_battery_get_date(const char *s, int *out)
> +{
> +	if (!isdigit(s[0]) || !isdigit(s[1]))
> +		return -EOPNOTSUPP;
> +
> +	*out = (s[0] - '0') * 10 + s[1] - '0';
> +	return 0;
> +}
> +
> +static int macsmc_battery_get_capacity_level(struct macsmc_power *power)
> +{
> +	bool flag;
> +	u32 val;
> +	int ret;
> +
> +	/* Check for emergency shutdown condition */
> +	if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val) >= 0 && val)
> +		return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
> +
> +	/* Check AC status for whether we could boot in this state */
> +	if (apple_smc_read_u32(power->smc, SMC_KEY(ACSt), &val) >= 0) {
> +		if (!(val & ACSt_CAN_BOOT_IBOOT))
> +			return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
> +
> +		if (!(val & ACSt_CAN_BOOT_AP))
> +			return POWER_SUPPLY_CAPACITY_LEVEL_LOW;
> +	}
> +
> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(BSFC), &flag);

the comment in the downstream driver what the flag is helpful

> +	if (ret < 0)
> +		return POWER_SUPPLY_CAPACITY_LEVEL_UNKNOWN;
> +
> +	if (flag)
> +		return POWER_SUPPLY_CAPACITY_LEVEL_FULL;
> +	else
> +		return POWER_SUPPLY_CAPACITY_LEVEL_NORMAL;
> +}
> +
> +static int macsmc_battery_get_property(struct power_supply *psy,
> +				       enum power_supply_property psp,
> +				       union power_supply_propval *val)
> +{
> +	struct macsmc_power *power = power_supply_get_drvdata(psy);
> +	int ret = 0;
> +	u8 vu8;
> +	u16 vu16;
> +	s16 vs16;
> +	s32 vs32;
> +	s64 vs64;
> +	bool flag;
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_STATUS:
> +		val->intval = macsmc_battery_get_status(power);
> +		ret = val->intval < 0 ? val->intval : 0;
> +		break;
> +	case POWER_SUPPLY_PROP_PRESENT:
> +		val->intval = 1;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
> +		val->intval = macsmc_battery_get_charge_behaviour(power);
> +		ret = val->intval < 0 ? val->intval : 0;
> +		break;
> +	case POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0TE), &vu16);
> +		val->intval = vu16 == 0xffff ? 0 : vu16 * 60;
> +		break;
> +	case POWER_SUPPLY_PROP_TIME_TO_FULL_NOW:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0TF), &vu16);
> +		val->intval = vu16 == 0xffff ? 0 : vu16 * 60;
> +		break;
> +	case POWER_SUPPLY_PROP_CAPACITY:
> +		ret = apple_smc_read_u8(power->smc, SMC_KEY(BUIC), &vu8);
> +		val->intval = vu8;
> +		break;
> +	case POWER_SUPPLY_PROP_CAPACITY_LEVEL:
> +		val->intval = macsmc_battery_get_capacity_level(power);
> +		ret = val->intval < 0 ? val->intval : 0;
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_CURRENT_NOW:
> +		ret = apple_smc_read_s16(power->smc, SMC_KEY(B0AC), &vs16);
> +		val->intval = vs16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_POWER_NOW:
> +		ret = apple_smc_read_s32(power->smc, SMC_KEY(B0AP), &vs32);
> +		val->intval = vs32 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(BITV), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
> +		/* Calculate total max design voltage from per-cell maximum voltage */
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(BVVN), &vu16);
> +		val->intval = vu16 * 1000 * power->num_cells;
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_MIN:
> +		/* Lifetime min */
> +		ret = apple_smc_read_s16(power->smc, SMC_KEY(BLPM), &vs16);
> +		val->intval = vs16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_MAX:
> +		/* Lifetime max */
> +		ret = apple_smc_read_s16(power->smc, SMC_KEY(BLPX), &vs16);
> +		val->intval = vs16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RC), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT_MAX:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RI), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RV), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0DC), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_FULL:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0FC), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_NOW:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RM), &vu16);
> +		/* B0RM is Big Endian, likely pass through from TI gas gauge */
> +		val->intval = (s16)swab16(vu16) * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0DC), &vu16);
> +		val->intval = vu16 * power->nominal_voltage_mv;
> +		break;
> +	case POWER_SUPPLY_PROP_ENERGY_FULL:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0FC), &vu16);
> +		val->intval = vu16 * power->nominal_voltage_mv;
> +		break;
> +	case POWER_SUPPLY_PROP_ENERGY_NOW:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RM), &vu16);
> +		/* B0RM is Big Endian, likely pass through from TI gas gauge */
> +		val->intval = (s16)swab16(vu16) * power->nominal_voltage_mv;
> +		break;
> +	case POWER_SUPPLY_PROP_TEMP:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0AT), &vu16);
> +		val->intval = vu16 - 2732; /* Kelvin x10 to Celsius x10 */
> +		break;
> +	case POWER_SUPPLY_PROP_CHARGE_COUNTER:
> +		ret = apple_smc_read_s64(power->smc, SMC_KEY(BAAC), &vs64);
> +		val->intval = vs64;
> +		break;
> +	case POWER_SUPPLY_PROP_CYCLE_COUNT:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0CT), &vu16);
> +		val->intval = vu16;
> +		break;
> +	case POWER_SUPPLY_PROP_SCOPE:
> +		val->intval = POWER_SUPPLY_SCOPE_SYSTEM;
> +		break;
> +	case POWER_SUPPLY_PROP_HEALTH:
> +		flag = false;
> +		ret = apple_smc_read_flag(power->smc, SMC_KEY(BBAD), &flag);
> +		val->intval = flag ? POWER_SUPPLY_HEALTH_DEAD : POWER_SUPPLY_HEALTH_GOOD;
> +		break;
> +	case POWER_SUPPLY_PROP_MODEL_NAME:
> +		val->strval = power->model_name;
> +		break;
> +	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
> +		val->strval = power->serial_number;
> +		break;
> +	case POWER_SUPPLY_PROP_MANUFACTURE_YEAR:
> +		ret = macsmc_battery_get_date(&power->mfg_date[0], &val->intval);
> +		/* The SMC reports the manufacture year as an offset from 1992. */
> +		val->intval += 1992;
> +		break;
> +	case POWER_SUPPLY_PROP_MANUFACTURE_MONTH:
> +		ret = macsmc_battery_get_date(&power->mfg_date[2], &val->intval);
> +		break;
> +	case POWER_SUPPLY_PROP_MANUFACTURE_DAY:
> +		ret = macsmc_battery_get_date(&power->mfg_date[4], &val->intval);
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return ret;
> +}
> +
> +static int macsmc_battery_set_property(struct power_supply *psy,
> +				       enum power_supply_property psp,
> +				       const union power_supply_propval *val)
> +{
> +	struct macsmc_power *power = power_supply_get_drvdata(psy);
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
> +		return macsmc_battery_set_charge_behaviour(power, val->intval);
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int macsmc_battery_property_is_writeable(struct power_supply *psy,
> +						enum power_supply_property psp)
> +{
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static const struct power_supply_desc macsmc_battery_desc_template = {
> +	.name			= "macsmc-battery",
> +	.type			= POWER_SUPPLY_TYPE_BATTERY,
> +	.get_property		= macsmc_battery_get_property,
> +	.set_property		= macsmc_battery_set_property,
> +	.property_is_writeable	= macsmc_battery_property_is_writeable,
> +};
> +
> +static int macsmc_ac_get_property(struct power_supply *psy,
> +				  enum power_supply_property psp,
> +				  union power_supply_propval *val)
> +{
> +	struct macsmc_power *power = power_supply_get_drvdata(psy);
> +	int ret = 0;
> +	u16 vu16;
> +	u32 vu32;
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_ONLINE:
> +		ret = apple_smc_read_u32(power->smc, SMC_KEY(CHIS), &vu32);
> +		val->intval = !!vu32;
> +		break;
> +	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-n), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-i), &vu16);
> +		val->intval = vu16 * 1000;
> +		break;
> +	case POWER_SUPPLY_PROP_INPUT_POWER_LIMIT:
> +		ret = apple_smc_read_u32(power->smc, SMC_KEY(ACPW), &vu32);
> +		val->intval = vu32 * 1000;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return ret;
> +}
> +
> +static const struct power_supply_desc macsmc_ac_desc_template = {
> +	.name			= "macsmc-ac",
> +	.type			= POWER_SUPPLY_TYPE_MAINS,
> +	.get_property		= macsmc_ac_get_property,
> +};
> +
> +static void macsmc_power_critical_work(struct work_struct *wrk)
> +{
> +	struct macsmc_power *power = container_of(wrk, struct macsmc_power, critical_work);
> +	u16 bitv, b0av;
> +	u32 bcf0;
> +
> +	if (!power->batt)
> +		return;
> +
> +	/*
> +	 * EMERGENCY: Check voltage vs design minimum.
> +	 * If we are below BITV, the battery is physically exhausted.
> +	 * We must shut down NOW to protect the filesystem.
> +	 */
> +	if (apple_smc_read_u16(power->smc, SMC_KEY(BITV), &bitv) >= 0 &&
> +	    apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &b0av) >= 0 &&
> +	    b0av < bitv) {
> +		dev_emerg(power->dev,
> +			  "Battery voltage (%d mV) below design minimum (%d mV)! Emergency shutdown.\n",
> +			  b0av, bitv);
> +		kernel_power_off();
> +		return;

I don't think we should return here. kernel_power_off() may do
nothing in which case the orderly_poweroff(true) might save data.
I would protect it as well via power->shutdown_started like in the
downstream driver to avoid calling kernel_power_off() once per second
until the battery dies or the system shutsdown.

> +	}
> +
> +	/*
> +	 * Avoid duplicate attempts at orderly shutdown.
> +	 * Voltage check is above this as we may want to
> +	 * "upgrade" an orderly shutdown to a critical power
> +	 * off if voltage drops.
> +	 */
> +	if (power->shutdown_started || system_state > SYSTEM_RUNNING)
> +		return;
> +
> +	/*
> +	 * Check if SMC flagged the battery as empty.
> +	 * We trigger a graceful shutdown to let the OS save data.
> +	 */
> +	if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &bcf0) == 0 && bcf0 != 0) {
> +		power->shutdown_started = true;
> +		dev_crit(power->dev, "Battery critical (empty flag set). Triggering orderly shutdown.\n");
> +		orderly_poweroff(true);
> +	}
> +}
> +
> +static int macsmc_power_event(struct notifier_block *nb, unsigned long event, void *data)
> +{
> +	struct macsmc_power *power = container_of(nb, struct macsmc_power, nb);
> +
> +	/*
> +	 * SMC Event IDs are reverse-engineered.
> +	 * 0x71... indicates power/battery events.
> +	 */
> +	if ((event & 0xffffff00) == 0x71010100 || /* Charger status change */
> +	    (event & 0xffff0000) == 0x71060000 || /* Port charge state change */
> +	    (event & 0xffff0000) == 0x71130000) { /* Connector insert/remove event */
> +		if (power->batt)
> +			power_supply_changed(power->batt);
> +		if (power->ac)
> +			power_supply_changed(power->ac);
> +		return NOTIFY_OK;
> +	} else if (event == 0x71020000) {
> +		/* Critical battery warning */
> +		if (power->batt)
> +			schedule_work(&power->critical_work);
> +		return NOTIFY_OK;
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static int macsmc_power_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
> +	struct power_supply_config psy_cfg = {};
> +	struct macsmc_power *power;
> +	bool has_battery = false;
> +	bool has_ac_adapter = false;
> +	int ret = -ENODEV;
> +	bool flag;
> +	u16 vu16;
> +	u32 val32;
> +	enum power_supply_property *props;
> +	size_t nprops;
> +
> +	if (!smc)
> +		return -ENODEV;
> +
> +	power = devm_kzalloc(dev, sizeof(*power), GFP_KERNEL);
> +	if (!power)
> +		return -ENOMEM;
> +
> +	power->dev = dev;
> +	power->smc = smc;
> +	dev_set_drvdata(dev, power);
> +
> +	INIT_WORK(&power->critical_work, macsmc_power_critical_work);
> +	ret = devm_work_autocancel(dev, &power->critical_work, macsmc_power_critical_work);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Check for battery presence.
> +	 * B0AV is a fundamental key.
> +	 */
> +	if (apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16) == 0 &&
> +	    macsmc_battery_get_status(power) > POWER_SUPPLY_STATUS_UNKNOWN)
> +		has_battery = true;
> +
> +	/*
> +	 * Check for AC adapter presence.
> +	 * CHIS is a fundamental key.
> +	 */
> +	if (apple_smc_key_exists(smc, SMC_KEY(CHIS)))
> +		has_ac_adapter = true;
> +

I think a short circuit check for !(has_battery || has_ac_adapter) would
make sense here. The setup code for props is quite long. It should
return -ENODEV. ret is not -ENODEV. anymore since it was overwritten
with the return value of devm_work_autocancel()

> +	if (has_battery) {
> +		power->batt_desc = macsmc_battery_desc_template;
> +		props = devm_kcalloc(dev, MACSMC_MAX_BATT_PROPS,
> +				     sizeof(enum power_supply_property),
> +				     GFP_KERNEL);

I don't like the dynamic allocation for the props. I think we can
currently get way with static property arrays and so we should do that.
See my comments below

> +		if (!props)
> +			return -ENOMEM;
> +
> +		nprops = 0;
> +
> +		/* Fundamental properties */
> +		props[nprops++] = POWER_SUPPLY_PROP_STATUS;
> +		props[nprops++] = POWER_SUPPLY_PROP_PRESENT;
> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_NOW;
> +		props[nprops++] = POWER_SUPPLY_PROP_CURRENT_NOW;
> +		props[nprops++] = POWER_SUPPLY_PROP_POWER_NOW;
> +		props[nprops++] = POWER_SUPPLY_PROP_CAPACITY;
> +		props[nprops++] = POWER_SUPPLY_PROP_CAPACITY_LEVEL;
> +		props[nprops++] = POWER_SUPPLY_PROP_TEMP;
> +		props[nprops++] = POWER_SUPPLY_PROP_CYCLE_COUNT;
> +		props[nprops++] = POWER_SUPPLY_PROP_HEALTH;
> +		props[nprops++] = POWER_SUPPLY_PROP_SCOPE;
> +		props[nprops++] = POWER_SUPPLY_PROP_MODEL_NAME;
> +		props[nprops++] = POWER_SUPPLY_PROP_SERIAL_NUMBER;
> +		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_YEAR;
> +		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_MONTH;
> +		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_DAY;
> +
> +		/* Extended properties usually present */
> +		props[nprops++] = POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW;
> +		props[nprops++] = POWER_SUPPLY_PROP_TIME_TO_FULL_NOW;
> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN;
> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN;
> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MIN;
> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MAX;
> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT;
> +		props[nprops++] = POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT_MAX;
> +		props[nprops++] = POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE;
> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN;
> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_FULL;
> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_NOW;
> +		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN;
> +		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_FULL;
> +		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_NOW;
> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_COUNTER;
> +
> +		/* Detect features based on key availability */
> +		if (apple_smc_key_exists(smc, SMC_KEY(CHTE)))
> +			power->has_chte = true;
> +		if (apple_smc_key_exists(smc, SMC_KEY(CH0C)))
> +			power->has_ch0c = true;
> +		if (apple_smc_key_exists(smc, SMC_KEY(CH0I)))
> +			power->has_ch0i = true;
> +
> +		/* Reset "Optimised Battery Charging" flags to default state */
> +		if (power->has_chte)
> +			apple_smc_write_u32(smc, SMC_KEY(CHTE), 0);
> +		else if (power->has_ch0c)
> +			apple_smc_write_u8(smc, SMC_KEY(CH0C), 0);
> +
> +		if (power->has_ch0i)
> +			apple_smc_write_u8(smc, SMC_KEY(CH0I), 0);
> +
> +		apple_smc_write_u8(smc, SMC_KEY(CH0K), 0);
> +		apple_smc_write_u8(smc, SMC_KEY(CH0B), 0);
> +
> +		/* Configure charge behaviour if supported */
> +		if (power->has_ch0i || power->has_ch0c || power->has_chte) {
> +			props[nprops++] = POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR;

This is the only dynamic battery prop. With a static array we can simply
put it at the end of the array and set batt_desc.num_properties to array
size - 1 if none of the keys are available.

> +
> +			power->batt_desc.charge_behaviours =
> +				BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO);
> +
> +			if (power->has_ch0i)
> +				power->batt_desc.charge_behaviours |=
> +					BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE);
> +
> +			if (power->has_chte || power->has_ch0c)
> +				power->batt_desc.charge_behaviours |=
> +					BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE);
> +		}
> +
> +		/* Detect charge limit method (CHWA vs CHLS) */
> +		if (apple_smc_read_flag(power->smc, SMC_KEY(CHWA), &flag) == 0)
> +			power->has_chwa = true;
> +		else if (apple_smc_read_u16(power->smc, SMC_KEY(CHLS), &vu16) >= 0)
> +			power->has_chls = true;
> +
> +		power->batt_desc.properties = props;
> +		power->batt_desc.num_properties = nprops;
> +
> +		/* Fetch identity strings */
> +		apple_smc_read(smc, SMC_KEY(BMDN), power->model_name,
> +			       sizeof(power->model_name) - 1);
> +		apple_smc_read(smc, SMC_KEY(BMSN), power->serial_number,
> +			       sizeof(power->serial_number) - 1);
> +		apple_smc_read(smc, SMC_KEY(BMDT), power->mfg_date,
> +			       sizeof(power->mfg_date) - 1);
> +
> +		apple_smc_read_u8(power->smc, SMC_KEY(BNCB), &power->num_cells);
> +		power->nominal_voltage_mv = MACSMC_NOMINAL_CELL_VOLTAGE_MV * power->num_cells;
> +
> +		/* Enable critical shutdown notifications by reading status once */
> +		apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val32);
> +
> +		psy_cfg.drv_data = power;
> +		power->batt = devm_power_supply_register(dev, &power->batt_desc, &psy_cfg);
> +		if (IS_ERR(power->batt)) {
> +			dev_err_probe(dev, PTR_ERR(power->batt),
> +				      "Failed to register battery\n");
> +			/* Don't return failure yet; try AC registration first */
> +			power->batt = NULL;
> +		}
> +	} else {
> +		dev_dbg(dev, "No battery detected.\n");

I would drop this

> +	}
> +
> +	if (has_ac_adapter) {
> +		power->ac_desc = macsmc_ac_desc_template;
> +		props = devm_kcalloc(dev, MACSMC_MAX_AC_PROPS,
> +				     sizeof(enum power_supply_property),
> +				     GFP_KERNEL);
> +		if (!props)
> +			return -ENOMEM;
> +
> +		nprops = 0;
> +
> +		/* Online status is fundamental */
> +		props[nprops++] = POWER_SUPPLY_PROP_ONLINE;
> +
> +		/* Input power limits are usually available */
> +		if (apple_smc_key_exists(power->smc, SMC_KEY(ACPW)))
> +			props[nprops++] = POWER_SUPPLY_PROP_INPUT_POWER_LIMIT;
> +
> +		/* macOS 15.4+ firmware dropped legacy AC keys (AC-n, AC-i) */
> +		if (apple_smc_read_u16(power->smc, SMC_KEY(AC-n), &vu16) >= 0) {
> +			props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_NOW;
> +			props[nprops++] = POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT;
> +		}

we can do the same trick here assuming AC-n and AC-i are only present if
ACPW is present.

> +		power->ac_desc.properties = props;
> +		power->ac_desc.num_properties = nprops;
> +
> +		psy_cfg.drv_data = power;
> +		power->ac = devm_power_supply_register(dev, &power->ac_desc, &psy_cfg);
> +		if (IS_ERR(power->ac)) {
> +			dev_err_probe(dev, PTR_ERR(power->ac),
> +				      "Failed to register AC adapter\n");
> +			power->ac = NULL;
> +		}
> +	} else {
> +		dev_dbg(dev, "No A/C adapter detected.\n");

same here
> +	}
> +
> +	/* Final check: did we register anything? */
> +	if (!power->batt && !power->ac)
> +		return ret;

See my comment about the changed value of ret above

> +
> +	power->nb.notifier_call = macsmc_power_event;
> +	blocking_notifier_chain_register(&smc->event_handlers, &power->nb);
> +
> +	return 0;
> +}
> +
> +static void macsmc_power_remove(struct platform_device *pdev)
> +{
> +	struct macsmc_power *power = dev_get_drvdata(&pdev->dev);
> +
> +	blocking_notifier_chain_unregister(&power->smc->event_handlers, &power->nb);
> +}
> +
> +static const struct platform_device_id macsmc_power_id[] = {
> +	{ "macsmc-power" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(platform, macsmc_power_id);
> +
> +static struct platform_driver macsmc_power_driver = {
> +	.driver = {
> +		.name = "macsmc-power",
> +	},
> +	.id_table = macsmc_power_id,
> +	.probe = macsmc_power_probe,
> +	.remove = macsmc_power_remove,
> +};
> +module_platform_driver(macsmc_power_driver);
> +
> +MODULE_LICENSE("Dual MIT/GPL");
> +MODULE_DESCRIPTION("Apple SMC battery and power management driver");
> +MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
> +MODULE_AUTHOR("Michael Reeves <michael.reeves077@gmail.com>");
> 
> -- 
> 2.51.2

Janne

Re: [PATCH v3 1/2] power: supply: Add macsmc-power driver for Apple Silicon

[Nick Chan]

On 17/1/2026 20:26, Janne Grunau wrote:
> On Thu, Jan 15, 2026 at 06:08:15PM +1100, Michael Reeves via B4 Relay wrote:
>> From: Michael Reeves <michael.reeves077@gmail.com>
> 
> I think the driver is overall similar to the downstream AsahiLinux
> driver so please keep Hector as author.
> 
>> This driver provides battery and AC status monitoring for Apple Silicon
>> Macs via the SMC (System Management Controller). It supports
>> reporting capacity, voltage, current, and charging status.
>>
>> Co-developed-by: Hector Martin <marcan@marcan.st>
>> Signed-off-by: Hector Martin <marcan@marcan.st>
> 
> The downstream driver a quite a few more Co-developed-by:/Sobs. When I
> squashed the commits I decided to err on the safe side and included
> commit authors from incremental patches as Co-developed-by: Why did you
> drop those?
> 
>> Reviewed-by: Neal Gompa <neal@gompa.dev>
>> Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
>> ---
>>  MAINTAINERS                         |   1 +
>>  drivers/power/supply/Kconfig        |  11 +
>>  drivers/power/supply/Makefile       |   1 +
>>  drivers/power/supply/macsmc-power.c | 834 ++++++++++++++++++++++++++++++++++++
>>  4 files changed, 847 insertions(+)
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 6c7bd06dec7c..f776996121c9 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -2513,6 +2513,7 @@ F:	drivers/nvmem/apple-spmi-nvmem.c
>>  F:	drivers/phy/apple/
>>  F:	drivers/pinctrl/pinctrl-apple-gpio.c
>>  F:	drivers/power/reset/macsmc-reboot.c
>> +F:	drivers/power/supply/macsmc-power.c
>>  F:	drivers/pwm/pwm-apple.c
>>  F:	drivers/rtc/rtc-macsmc.c
>>  F:	drivers/soc/apple/*
>> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
>> index 92f9f7aae92f..3a5b7d9234c2 100644
>> --- a/drivers/power/supply/Kconfig
>> +++ b/drivers/power/supply/Kconfig
>> @@ -1132,4 +1132,15 @@ config FUEL_GAUGE_MM8013
>>  	  the state of charge, temperature, cycle count, actual and design
>>  	  capacity, etc.
>>  
>> +config MACSMC_POWER
>> +	tristate "Apple SMC Battery and Power Driver"
>> +	depends on MFD_MACSMC
>> +	help
>> +	  This driver provides support for the battery and AC adapter on
>> +	  Apple Silicon machines. It exposes battery telemetry (voltage,
>> +	  current, health) and AC adapter status through the standard Linux
>> +	  power supply framework.
>> +
>> +	  Say Y or M here if you have an Apple Silicon based Mac.
>> +
>>  endif # POWER_SUPPLY
>> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
>> index 4b79d5abc49a..d14420b606d8 100644
>> --- a/drivers/power/supply/Makefile
>> +++ b/drivers/power/supply/Makefile
>> @@ -128,3 +128,4 @@ obj-$(CONFIG_CHARGER_SURFACE)	+= surface_charger.o
>>  obj-$(CONFIG_BATTERY_UG3105)	+= ug3105_battery.o
>>  obj-$(CONFIG_CHARGER_QCOM_SMB2)	+= qcom_smbx.o
>>  obj-$(CONFIG_FUEL_GAUGE_MM8013)	+= mm8013.o
>> +obj-$(CONFIG_MACSMC_POWER)	+= macsmc-power.o
>> diff --git a/drivers/power/supply/macsmc-power.c b/drivers/power/supply/macsmc-power.c
>> new file mode 100644
>> index 000000000000..9b3faefe7a45
>> --- /dev/null
>> +++ b/drivers/power/supply/macsmc-power.c
>> @@ -0,0 +1,834 @@
>> +// SPDX-License-Identifier: GPL-2.0-only OR MIT
>> +/*
>> + * Apple SMC Power/Battery Management Driver
>> + *
>> + * This driver exposes battery telemetry (voltage, current, temperature, health)
>> + * and AC adapter status provided by the Apple SMC (System Management Controller)
>> + * on Apple Silicon systems.
>> + *
>> + * Copyright The Asahi Linux Contributors
>> + */
>> +
>> +#include <linux/ctype.h>
>> +#include <linux/delay.h>
>> +#include <linux/devm-helpers.h>
>> +#include <linux/limits.h>
>> +#include <linux/module.h>
>> +#include <linux/mfd/macsmc.h>
>> +#include <linux/notifier.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/power_supply.h>
>> +#include <linux/reboot.h>
>> +#include <linux/workqueue.h>
>> +
>> +#define MAX_STRING_LENGTH 256
>> +
>> +/*
>> + * The SMC reports charge in mAh (Coulombs) but energy in mWh (Joules).
>> + * We lack a register for "Nominal Voltage" or "Energy Accumulator".
>> + * We use a fixed 3.8V/cell constant to approximate energy stats for userspace,
>> + * derived from empirical data across supported MacBook models.
>> + */
>> +#define MACSMC_NOMINAL_CELL_VOLTAGE_MV 3800
>> +
>> +/* SMC Key Flags */
>> +#define CHNC_BATTERY_FULL	BIT(0)
>> +#define CHNC_NO_CHARGER		BIT(7)
>> +#define CHNC_NOCHG_CH0C		BIT(14)
>> +#define CHNC_NOCHG_CH0B_CH0K	BIT(15)
>> +#define CHNC_BATTERY_FULL_2	BIT(18)
>> +#define CHNC_BMS_BUSY		BIT(23)
>> +#define CHNC_CHLS_LIMIT		BIT(24)
>> +#define CHNC_NOAC_CH0J		BIT(53)
>> +#define CHNC_NOAC_CH0I		BIT(54)
>> +
>> +#define CH0R_LOWER_FLAGS	GENMASK(15, 0)
>> +#define CH0R_NOAC_CH0I		BIT(0)
>> +#define CH0R_NOAC_DISCONNECTED	BIT(4)
>> +#define CH0R_NOAC_CH0J		BIT(5)
>> +#define CH0R_BMS_BUSY		BIT(8)
>> +#define CH0R_NOAC_CH0K		BIT(9)
>> +#define CH0R_NOAC_CHWA		BIT(11)
>> +
>> +#define CH0X_CH0C		BIT(0)
>> +#define CH0X_CH0B		BIT(1)
>> +
>> +#define ACSt_CAN_BOOT_AP	BIT(2)
>> +#define ACSt_CAN_BOOT_IBOOT	BIT(1)
>> +
>> +#define CHWA_CHLS_FIXED_START_OFFSET	5
>> +#define CHLS_MIN_END_THRESHOLD		10
>> +#define CHLS_FORCE_DISCHARGE		0x100
>> +#define CHWA_FIXED_END_THRESHOLD	80
>> +#define CHWA_PROP_WRITE_THRESHOLD	95
>> +
>> +#define MACSMC_MAX_BATT_PROPS		50
>> +#define MACSMC_MAX_AC_PROPS		10
>> +
>> +struct macsmc_power {
>> +	struct device *dev;
>> +	struct apple_smc *smc;
>> +
>> +	struct power_supply_desc ac_desc;
>> +	struct power_supply_desc batt_desc;
>> +
>> +	struct power_supply *batt;
>> +	struct power_supply *ac;
>> +
>> +	char model_name[MAX_STRING_LENGTH];
>> +	char serial_number[MAX_STRING_LENGTH];
>> +	char mfg_date[MAX_STRING_LENGTH];
>> +
>> +	bool has_chwa;
>> +	bool has_chls;
>> +	bool has_ch0i;
>> +	bool has_ch0c;
>> +	bool has_chte;
> 
> I think comments what these keys do and in which firmware version the
> appeared or vanished would be helpful here. I can Help with digging
> through the history.
> 
>> +
>> +	u8 num_cells;
>> +	int nominal_voltage_mv;
>> +
>> +	struct notifier_block nb;
>> +	struct work_struct critical_work;
>> +	bool shutdown_started;
>> +};
>> +
>> +static int macsmc_battery_get_status(struct macsmc_power *power)
>> +{
>> +	u64 nocharge_flags;
>> +	u32 nopower_flags;
>> +	u16 ac_current;
>> +	int charge_limit = 0;
>> +	bool limited = false;
>> +	bool flag;
>> +	int ret;
>> +
>> +	/*
>> +	 * Fallbacks exist for keys that may disappear in future hardware.
>> +	 * CHCE/CHCC/BSFC/CHSC are considered fundamental; absence is an error.
>> +	 */
> 
> Why did you rewrite this (and many other) comments? I don't think this
> is an improvement over the comment in the downstream driver.
> 
>> +	/* Check if power input is inhibited (e.g. BMS balancing cycle) */
>> +	ret = apple_smc_read_u32(power->smc, SMC_KEY(CH0R), &nopower_flags);
>> +	if (!ret && (nopower_flags & CH0R_LOWER_FLAGS & ~CH0R_BMS_BUSY))
>> +		return POWER_SUPPLY_STATUS_DISCHARGING;
>> +
>> +	/* Check if charger is present */
>> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHCE), &flag);
>> +	if (ret < 0)
>> +		return ret;
>> +	if (!flag)
>> +		return POWER_SUPPLY_STATUS_DISCHARGING;
>> +
>> +	/* Check if AC is charge capable */
>> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHCC), &flag);
>> +	if (ret < 0)
>> +		return ret;
>> +	if (!flag)
>> +		return POWER_SUPPLY_STATUS_DISCHARGING;
>> +
>> +	/* Check if AC input limit is too low */
>> +	ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-i), &ac_current);
>> +	if (!ret && ac_current < 100)
>> +		return POWER_SUPPLY_STATUS_DISCHARGING;
>> +
>> +	/* Check if battery is full */
>> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(BSFC), &flag);
>> +	if (ret < 0)
>> +		return ret;
>> +	if (flag)
>> +		return POWER_SUPPLY_STATUS_FULL;
>> +
>> +	/* Check for user-defined charge limits */
>> +	if (power->has_chls) {
>> +		u16 vu16;
>> +
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(CHLS), &vu16);
>> +		if (ret == 0 && (vu16 & 0xff) >= CHLS_MIN_END_THRESHOLD)
>> +			charge_limit = (vu16 & 0xff) - CHWA_CHLS_FIXED_START_OFFSET;
>> +	} else if (power->has_chwa) {
>> +		ret = apple_smc_read_flag(power->smc, SMC_KEY(CHWA), &flag);
>> +		if (ret == 0 && flag)
>> +			charge_limit = CHWA_FIXED_END_THRESHOLD - CHWA_CHLS_FIXED_START_OFFSET;
>> +	}
>> +
>> +	if (charge_limit > 0) {
>> +		u8 buic = 0;
>> +
>> +		if (apple_smc_read_u8(power->smc, SMC_KEY(BUIC), &buic) >= 0 &&
>> +		    buic >= charge_limit)
>> +			limited = true;
>> +	}
>> +
>> +	/* Check charging inhibitors */
>> +	ret = apple_smc_read_u64(power->smc, SMC_KEY(CHNC), &nocharge_flags);
>> +	if (!ret) {
>> +		if (nocharge_flags & CHNC_BATTERY_FULL)
>> +			return POWER_SUPPLY_STATUS_FULL;
>> +		/* BMS busy shows up as inhibit, but we treat it as charging */
>> +		else if (nocharge_flags == CHNC_BMS_BUSY && !limited)
>> +			return POWER_SUPPLY_STATUS_CHARGING;
>> +		else if (nocharge_flags)
>> +			return POWER_SUPPLY_STATUS_NOT_CHARGING;
>> +		else
>> +			return POWER_SUPPLY_STATUS_CHARGING;
>> +	}
>> +
>> +	/* Fallback: System charging flag */
>> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(CHSC), &flag);
>> +	if (ret < 0)
>> +		return ret;
>> +	if (!flag)
>> +		return POWER_SUPPLY_STATUS_NOT_CHARGING;
>> +
>> +	return POWER_SUPPLY_STATUS_CHARGING;
>> +}
>> +
>> +static int macsmc_battery_get_charge_behaviour(struct macsmc_power *power)
>> +{
>> +	int ret;
>> +	u8 val8;
>> +	u8 chte_buf[4];
>> +
>> +	if (power->has_ch0i) {
>> +		ret = apple_smc_read_u8(power->smc, SMC_KEY(CH0I), &val8);
>> +		if (ret)
>> +			return ret;
>> +		if (val8 & CH0R_NOAC_CH0I)
>> +			return POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE;
>> +	}
>> +
>> +	if (power->has_chte) {
>> +		ret = apple_smc_read(power->smc, SMC_KEY(CHTE), chte_buf, 4);
>> +		if (ret < 0)
>> +			return ret;
>> +
>> +		if (chte_buf[0] == 0x01)
>> +			return POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE;
>> +	} else if (power->has_ch0c) {
>> +		ret = apple_smc_read_u8(power->smc, SMC_KEY(CH0C), &val8);
>> +		if (ret)
>> +			return ret;
>> +		if (val8 & CH0X_CH0C)
>> +			return POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE;
>> +	}
>> +
>> +	return POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO;
>> +}
>> +
>> +static int macsmc_battery_set_charge_behaviour(struct macsmc_power *power, int val)
>> +{
>> +	int ret;
>> +
>> +	/* First, reset all inhibitors to a known-good 'auto' state */
> 
> why? I wouldn't expect this function to make any if `val` is not
> supported. If has_ch0i is not true
> POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE will reset inhibit charge
> and return -EOPNOTSUPP which is unexpected.
> Resetting the values first and then change them to the actual desired
> values doesn't make much sense either.
> Yes, it's a little annoying to make the same calls in multiple cases of
> the switch statement but you could move the `power->has_*` checks and
> the smc writes to a single line.
> 
>> +	if (power->has_ch0i) {
>> +		ret = apple_smc_write_u8(power->smc, SMC_KEY(CH0I), 0);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	if (power->has_chte) {
>> +		ret = apple_smc_write_u32(power->smc, SMC_KEY(CHTE), 0);
>> +		if (ret)
>> +			return ret;
>> +	} else if (power->has_ch0c) {
>> +		ret = apple_smc_write_u8(power->smc, SMC_KEY(CH0C), 0);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +
>> +	switch (val) {
>> +	case POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO:
>> +		return 0;
>> +
>> +	case POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE:
>> +		if (power->has_chte)
>> +			return apple_smc_write_u32(power->smc, SMC_KEY(CHTE), 1);
>> +		else if (power->has_ch0c)
>> +			return apple_smc_write_u8(power->smc, SMC_KEY(CH0C), 1);
>> +		else
>> +			return -EOPNOTSUPP;
>> +		break;
>> +
>> +	case POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE:
>> +		if (!power->has_ch0i)
>> +			return -EOPNOTSUPP;
>> +		return apple_smc_write_u8(power->smc, SMC_KEY(CH0I), 1);
>> +
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +}
>> +
>> +static int macsmc_battery_get_date(const char *s, int *out)
>> +{
>> +	if (!isdigit(s[0]) || !isdigit(s[1]))
>> +		return -EOPNOTSUPP;
>> +
>> +	*out = (s[0] - '0') * 10 + s[1] - '0';
>> +	return 0;
>> +}
>> +
>> +static int macsmc_battery_get_capacity_level(struct macsmc_power *power)
>> +{
>> +	bool flag;
>> +	u32 val;
>> +	int ret;
>> +
>> +	/* Check for emergency shutdown condition */
>> +	if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val) >= 0 && val)
>> +		return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
>> +
>> +	/* Check AC status for whether we could boot in this state */
>> +	if (apple_smc_read_u32(power->smc, SMC_KEY(ACSt), &val) >= 0) {
>> +		if (!(val & ACSt_CAN_BOOT_IBOOT))
>> +			return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
>> +
>> +		if (!(val & ACSt_CAN_BOOT_AP))
>> +			return POWER_SUPPLY_CAPACITY_LEVEL_LOW;
>> +	}
>> +
>> +	ret = apple_smc_read_flag(power->smc, SMC_KEY(BSFC), &flag);
> 
> the comment in the downstream driver what the flag is helpful
> 
>> +	if (ret < 0)
>> +		return POWER_SUPPLY_CAPACITY_LEVEL_UNKNOWN;
>> +
>> +	if (flag)
>> +		return POWER_SUPPLY_CAPACITY_LEVEL_FULL;
>> +	else
>> +		return POWER_SUPPLY_CAPACITY_LEVEL_NORMAL;
>> +}
>> +
>> +static int macsmc_battery_get_property(struct power_supply *psy,
>> +				       enum power_supply_property psp,
>> +				       union power_supply_propval *val)
>> +{
>> +	struct macsmc_power *power = power_supply_get_drvdata(psy);
>> +	int ret = 0;
>> +	u8 vu8;
>> +	u16 vu16;
>> +	s16 vs16;
>> +	s32 vs32;
>> +	s64 vs64;
>> +	bool flag;
>> +
>> +	switch (psp) {
>> +	case POWER_SUPPLY_PROP_STATUS:
>> +		val->intval = macsmc_battery_get_status(power);
>> +		ret = val->intval < 0 ? val->intval : 0;
>> +		break;
>> +	case POWER_SUPPLY_PROP_PRESENT:
>> +		val->intval = 1;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
>> +		val->intval = macsmc_battery_get_charge_behaviour(power);
>> +		ret = val->intval < 0 ? val->intval : 0;
>> +		break;
>> +	case POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0TE), &vu16);
>> +		val->intval = vu16 == 0xffff ? 0 : vu16 * 60;
>> +		break;
>> +	case POWER_SUPPLY_PROP_TIME_TO_FULL_NOW:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0TF), &vu16);
>> +		val->intval = vu16 == 0xffff ? 0 : vu16 * 60;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CAPACITY:
>> +		ret = apple_smc_read_u8(power->smc, SMC_KEY(BUIC), &vu8);
>> +		val->intval = vu8;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CAPACITY_LEVEL:
>> +		val->intval = macsmc_battery_get_capacity_level(power);
>> +		ret = val->intval < 0 ? val->intval : 0;
>> +		break;
>> +	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CURRENT_NOW:
>> +		ret = apple_smc_read_s16(power->smc, SMC_KEY(B0AC), &vs16);
>> +		val->intval = vs16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_POWER_NOW:
>> +		ret = apple_smc_read_s32(power->smc, SMC_KEY(B0AP), &vs32);
>> +		val->intval = vs32 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(BITV), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
>> +		/* Calculate total max design voltage from per-cell maximum voltage */
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(BVVN), &vu16);
>> +		val->intval = vu16 * 1000 * power->num_cells;
>> +		break;
>> +	case POWER_SUPPLY_PROP_VOLTAGE_MIN:
>> +		/* Lifetime min */
>> +		ret = apple_smc_read_s16(power->smc, SMC_KEY(BLPM), &vs16);
>> +		val->intval = vs16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_VOLTAGE_MAX:
>> +		/* Lifetime max */
>> +		ret = apple_smc_read_s16(power->smc, SMC_KEY(BLPX), &vs16);
>> +		val->intval = vs16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RC), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT_MAX:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RI), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RV), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0DC), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CHARGE_FULL:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0FC), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CHARGE_NOW:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RM), &vu16);
>> +		/* B0RM is Big Endian, likely pass through from TI gas gauge */
>> +		val->intval = (s16)swab16(vu16) * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0DC), &vu16);
>> +		val->intval = vu16 * power->nominal_voltage_mv;
>> +		break;
>> +	case POWER_SUPPLY_PROP_ENERGY_FULL:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0FC), &vu16);
>> +		val->intval = vu16 * power->nominal_voltage_mv;
>> +		break;
>> +	case POWER_SUPPLY_PROP_ENERGY_NOW:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0RM), &vu16);
>> +		/* B0RM is Big Endian, likely pass through from TI gas gauge */
>> +		val->intval = (s16)swab16(vu16) * power->nominal_voltage_mv;
>> +		break;
>> +	case POWER_SUPPLY_PROP_TEMP:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0AT), &vu16);
>> +		val->intval = vu16 - 2732; /* Kelvin x10 to Celsius x10 */
>> +		break;
>> +	case POWER_SUPPLY_PROP_CHARGE_COUNTER:
>> +		ret = apple_smc_read_s64(power->smc, SMC_KEY(BAAC), &vs64);
>> +		val->intval = vs64;
>> +		break;
>> +	case POWER_SUPPLY_PROP_CYCLE_COUNT:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(B0CT), &vu16);
>> +		val->intval = vu16;
>> +		break;
>> +	case POWER_SUPPLY_PROP_SCOPE:
>> +		val->intval = POWER_SUPPLY_SCOPE_SYSTEM;
>> +		break;
>> +	case POWER_SUPPLY_PROP_HEALTH:
>> +		flag = false;
>> +		ret = apple_smc_read_flag(power->smc, SMC_KEY(BBAD), &flag);
>> +		val->intval = flag ? POWER_SUPPLY_HEALTH_DEAD : POWER_SUPPLY_HEALTH_GOOD;
>> +		break;
>> +	case POWER_SUPPLY_PROP_MODEL_NAME:
>> +		val->strval = power->model_name;
>> +		break;
>> +	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
>> +		val->strval = power->serial_number;
>> +		break;
>> +	case POWER_SUPPLY_PROP_MANUFACTURE_YEAR:
>> +		ret = macsmc_battery_get_date(&power->mfg_date[0], &val->intval);
>> +		/* The SMC reports the manufacture year as an offset from 1992. */
>> +		val->intval += 1992;
>> +		break;
>> +	case POWER_SUPPLY_PROP_MANUFACTURE_MONTH:
>> +		ret = macsmc_battery_get_date(&power->mfg_date[2], &val->intval);
>> +		break;
>> +	case POWER_SUPPLY_PROP_MANUFACTURE_DAY:
>> +		ret = macsmc_battery_get_date(&power->mfg_date[4], &val->intval);
>> +		break;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +static int macsmc_battery_set_property(struct power_supply *psy,
>> +				       enum power_supply_property psp,
>> +				       const union power_supply_propval *val)
>> +{
>> +	struct macsmc_power *power = power_supply_get_drvdata(psy);
>> +
>> +	switch (psp) {
>> +	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
>> +		return macsmc_battery_set_charge_behaviour(power, val->intval);
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +}
>> +
>> +static int macsmc_battery_property_is_writeable(struct power_supply *psy,
>> +						enum power_supply_property psp)
>> +{
>> +	switch (psp) {
>> +	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
>> +		return true;
>> +	default:
>> +		return false;
>> +	}
>> +}
>> +
>> +static const struct power_supply_desc macsmc_battery_desc_template = {
>> +	.name			= "macsmc-battery",
>> +	.type			= POWER_SUPPLY_TYPE_BATTERY,
>> +	.get_property		= macsmc_battery_get_property,
>> +	.set_property		= macsmc_battery_set_property,
>> +	.property_is_writeable	= macsmc_battery_property_is_writeable,
>> +};
>> +
>> +static int macsmc_ac_get_property(struct power_supply *psy,
>> +				  enum power_supply_property psp,
>> +				  union power_supply_propval *val)
>> +{
>> +	struct macsmc_power *power = power_supply_get_drvdata(psy);
>> +	int ret = 0;
>> +	u16 vu16;
>> +	u32 vu32;
>> +
>> +	switch (psp) {
>> +	case POWER_SUPPLY_PROP_ONLINE:
>> +		ret = apple_smc_read_u32(power->smc, SMC_KEY(CHIS), &vu32);
>> +		val->intval = !!vu32;
>> +		break;
>> +	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-n), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
>> +		ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-i), &vu16);
>> +		val->intval = vu16 * 1000;
>> +		break;
>> +	case POWER_SUPPLY_PROP_INPUT_POWER_LIMIT:
>> +		ret = apple_smc_read_u32(power->smc, SMC_KEY(ACPW), &vu32);
>> +		val->intval = vu32 * 1000;
>> +		break;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +static const struct power_supply_desc macsmc_ac_desc_template = {
>> +	.name			= "macsmc-ac",
>> +	.type			= POWER_SUPPLY_TYPE_MAINS,
>> +	.get_property		= macsmc_ac_get_property,
>> +};
>> +
>> +static void macsmc_power_critical_work(struct work_struct *wrk)
>> +{
>> +	struct macsmc_power *power = container_of(wrk, struct macsmc_power, critical_work);
>> +	u16 bitv, b0av;
>> +	u32 bcf0;
>> +
>> +	if (!power->batt)
>> +		return;
>> +
>> +	/*
>> +	 * EMERGENCY: Check voltage vs design minimum.
>> +	 * If we are below BITV, the battery is physically exhausted.
>> +	 * We must shut down NOW to protect the filesystem.
>> +	 */
>> +	if (apple_smc_read_u16(power->smc, SMC_KEY(BITV), &bitv) >= 0 &&
>> +	    apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &b0av) >= 0 &&
>> +	    b0av < bitv) {
>> +		dev_emerg(power->dev,
>> +			  "Battery voltage (%d mV) below design minimum (%d mV)! Emergency shutdown.\n",
>> +			  b0av, bitv);
>> +		kernel_power_off();
>> +		return;
> 
> I don't think we should return here. kernel_power_off() may do
> nothing in which case the orderly_poweroff(true) might save data.
> I would protect it as well via power->shutdown_started like in the
> downstream driver to avoid calling kernel_power_off() once per second
> until the battery dies or the system shutsdown.
> 
>> +	}
>> +
>> +	/*
>> +	 * Avoid duplicate attempts at orderly shutdown.
>> +	 * Voltage check is above this as we may want to
>> +	 * "upgrade" an orderly shutdown to a critical power
>> +	 * off if voltage drops.
>> +	 */
>> +	if (power->shutdown_started || system_state > SYSTEM_RUNNING)
>> +		return;
>> +
>> +	/*
>> +	 * Check if SMC flagged the battery as empty.
>> +	 * We trigger a graceful shutdown to let the OS save data.
>> +	 */
>> +	if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &bcf0) == 0 && bcf0 != 0) {
>> +		power->shutdown_started = true;
>> +		dev_crit(power->dev, "Battery critical (empty flag set). Triggering orderly shutdown.\n");
>> +		orderly_poweroff(true);
>> +	}
>> +}
>> +
>> +static int macsmc_power_event(struct notifier_block *nb, unsigned long event, void *data)
>> +{
>> +	struct macsmc_power *power = container_of(nb, struct macsmc_power, nb);
>> +
>> +	/*
>> +	 * SMC Event IDs are reverse-engineered.
>> +	 * 0x71... indicates power/battery events.
>> +	 */
>> +	if ((event & 0xffffff00) == 0x71010100 || /* Charger status change */
>> +	    (event & 0xffff0000) == 0x71060000 || /* Port charge state change */
>> +	    (event & 0xffff0000) == 0x71130000) { /* Connector insert/remove event */
>> +		if (power->batt)
>> +			power_supply_changed(power->batt);
>> +		if (power->ac)
>> +			power_supply_changed(power->ac);
>> +		return NOTIFY_OK;
>> +	} else if (event == 0x71020000) {
>> +		/* Critical battery warning */
>> +		if (power->batt)
>> +			schedule_work(&power->critical_work);
>> +		return NOTIFY_OK;
>> +	}
>> +
>> +	return NOTIFY_DONE;
>> +}
>> +
>> +static int macsmc_power_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
>> +	struct power_supply_config psy_cfg = {};
>> +	struct macsmc_power *power;
>> +	bool has_battery = false;
>> +	bool has_ac_adapter = false;
>> +	int ret = -ENODEV;
>> +	bool flag;
>> +	u16 vu16;
>> +	u32 val32;
>> +	enum power_supply_property *props;
>> +	size_t nprops;
>> +
>> +	if (!smc)
>> +		return -ENODEV;
>> +
>> +	power = devm_kzalloc(dev, sizeof(*power), GFP_KERNEL);
>> +	if (!power)
>> +		return -ENOMEM;
>> +
>> +	power->dev = dev;
>> +	power->smc = smc;
>> +	dev_set_drvdata(dev, power);
>> +
>> +	INIT_WORK(&power->critical_work, macsmc_power_critical_work);
>> +	ret = devm_work_autocancel(dev, &power->critical_work, macsmc_power_critical_work);
>> +	if (ret)
>> +		return ret;
>> +
>> +	/*
>> +	 * Check for battery presence.
>> +	 * B0AV is a fundamental key.
>> +	 */
>> +	if (apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16) == 0 &&
>> +	    macsmc_battery_get_status(power) > POWER_SUPPLY_STATUS_UNKNOWN)
>> +		has_battery = true;
>> +
>> +	/*
>> +	 * Check for AC adapter presence.
>> +	 * CHIS is a fundamental key.
>> +	 */
>> +	if (apple_smc_key_exists(smc, SMC_KEY(CHIS)))
>> +		has_ac_adapter = true;
>> +
> 
> I think a short circuit check for !(has_battery || has_ac_adapter) would
> make sense here. The setup code for props is quite long. It should
> return -ENODEV. ret is not -ENODEV. anymore since it was overwritten
> with the return value of devm_work_autocancel()
> 
>> +	if (has_battery) {
>> +		power->batt_desc = macsmc_battery_desc_template;
>> +		props = devm_kcalloc(dev, MACSMC_MAX_BATT_PROPS,
>> +				     sizeof(enum power_supply_property),
>> +				     GFP_KERNEL);
> 
> I don't like the dynamic allocation for the props. I think we can
> currently get way with static property arrays and so we should do that.
> See my comments below

Dynamic allocation is needed to properly add support pre-M1 support,
as the SMCs in them misses a few keys, yet in iOS 16 the charge limit
(CHWA) keys are added. In a similar way, there really is no sane way
to add any new properties for M1/M2/M3 with static allocation. So I
would prefer if dynamic allocation is kept.

> 
>> +		if (!props)
>> +			return -ENOMEM;
>> +
>> +		nprops = 0;
>> +
>> +		/* Fundamental properties */
>> +		props[nprops++] = POWER_SUPPLY_PROP_STATUS;
>> +		props[nprops++] = POWER_SUPPLY_PROP_PRESENT;
>> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_NOW;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CURRENT_NOW;
>> +		props[nprops++] = POWER_SUPPLY_PROP_POWER_NOW;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CAPACITY;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CAPACITY_LEVEL;
>> +		props[nprops++] = POWER_SUPPLY_PROP_TEMP;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CYCLE_COUNT;
>> +		props[nprops++] = POWER_SUPPLY_PROP_HEALTH;
>> +		props[nprops++] = POWER_SUPPLY_PROP_SCOPE;
>> +		props[nprops++] = POWER_SUPPLY_PROP_MODEL_NAME;
>> +		props[nprops++] = POWER_SUPPLY_PROP_SERIAL_NUMBER;
>> +		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_YEAR;
>> +		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_MONTH;
>> +		props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_DAY;
>> +
>> +		/* Extended properties usually present */
>> +		props[nprops++] = POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW;
>> +		props[nprops++] = POWER_SUPPLY_PROP_TIME_TO_FULL_NOW;
>> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN;
>> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN;
>> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MIN;
>> +		props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MAX;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT_MAX;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_FULL;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_NOW;
>> +		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN;
>> +		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_FULL;
>> +		props[nprops++] = POWER_SUPPLY_PROP_ENERGY_NOW;
>> +		props[nprops++] = POWER_SUPPLY_PROP_CHARGE_COUNTER;
>> +
>> +		/* Detect features based on key availability */
>> +		if (apple_smc_key_exists(smc, SMC_KEY(CHTE)))
>> +			power->has_chte = true;
>> +		if (apple_smc_key_exists(smc, SMC_KEY(CH0C)))
>> +			power->has_ch0c = true;
>> +		if (apple_smc_key_exists(smc, SMC_KEY(CH0I)))
>> +			power->has_ch0i = true;
>> +
>> +		/* Reset "Optimised Battery Charging" flags to default state */
>> +		if (power->has_chte)
>> +			apple_smc_write_u32(smc, SMC_KEY(CHTE), 0);
>> +		else if (power->has_ch0c)
>> +			apple_smc_write_u8(smc, SMC_KEY(CH0C), 0);
>> +
>> +		if (power->has_ch0i)
>> +			apple_smc_write_u8(smc, SMC_KEY(CH0I), 0);
>> +
>> +		apple_smc_write_u8(smc, SMC_KEY(CH0K), 0);
>> +		apple_smc_write_u8(smc, SMC_KEY(CH0B), 0);
>> +
>> +		/* Configure charge behaviour if supported */
>> +		if (power->has_ch0i || power->has_ch0c || power->has_chte) {
>> +			props[nprops++] = POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR;
> 
> This is the only dynamic battery prop. With a static array we can simply
> put it at the end of the array and set batt_desc.num_properties to array
> size - 1 if none of the keys are available.

See my comment above.

> 
>> +
>> +			power->batt_desc.charge_behaviours =
>> +				BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO);
>> +
>> +			if (power->has_ch0i)
>> +				power->batt_desc.charge_behaviours |=
>> +					BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE);
>> +
>> +			if (power->has_chte || power->has_ch0c)
>> +				power->batt_desc.charge_behaviours |=
>> +					BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE);
>> +		}
>> +
>> +		/* Detect charge limit method (CHWA vs CHLS) */
>> +		if (apple_smc_read_flag(power->smc, SMC_KEY(CHWA), &flag) == 0)
>> +			power->has_chwa = true;
>> +		else if (apple_smc_read_u16(power->smc, SMC_KEY(CHLS), &vu16) >= 0)
>> +			power->has_chls = true;
>> +
>> +		power->batt_desc.properties = props;
>> +		power->batt_desc.num_properties = nprops;
>> +
>> +		/* Fetch identity strings */
>> +		apple_smc_read(smc, SMC_KEY(BMDN), power->model_name,
>> +			       sizeof(power->model_name) - 1);
>> +		apple_smc_read(smc, SMC_KEY(BMSN), power->serial_number,
>> +			       sizeof(power->serial_number) - 1);
>> +		apple_smc_read(smc, SMC_KEY(BMDT), power->mfg_date,
>> +			       sizeof(power->mfg_date) - 1);
>> +
>> +		apple_smc_read_u8(power->smc, SMC_KEY(BNCB), &power->num_cells);
>> +		power->nominal_voltage_mv = MACSMC_NOMINAL_CELL_VOLTAGE_MV * power->num_cells;
>> +
>> +		/* Enable critical shutdown notifications by reading status once */
>> +		apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val32);
>> +
>> +		psy_cfg.drv_data = power;
>> +		power->batt = devm_power_supply_register(dev, &power->batt_desc, &psy_cfg);
>> +		if (IS_ERR(power->batt)) {
>> +			dev_err_probe(dev, PTR_ERR(power->batt),
>> +				      "Failed to register battery\n");
>> +			/* Don't return failure yet; try AC registration first */
>> +			power->batt = NULL;
>> +		}
>> +	} else {
>> +		dev_dbg(dev, "No battery detected.\n");
> 
> I would drop this
> 
>> +	}
>> +
>> +	if (has_ac_adapter) {
>> +		power->ac_desc = macsmc_ac_desc_template;
>> +		props = devm_kcalloc(dev, MACSMC_MAX_AC_PROPS,
>> +				     sizeof(enum power_supply_property),
>> +				     GFP_KERNEL);
>> +		if (!props)
>> +			return -ENOMEM;
>> +
>> +		nprops = 0;
>> +
>> +		/* Online status is fundamental */
>> +		props[nprops++] = POWER_SUPPLY_PROP_ONLINE;
>> +
>> +		/* Input power limits are usually available */
>> +		if (apple_smc_key_exists(power->smc, SMC_KEY(ACPW)))
>> +			props[nprops++] = POWER_SUPPLY_PROP_INPUT_POWER_LIMIT;
>> +
>> +		/* macOS 15.4+ firmware dropped legacy AC keys (AC-n, AC-i) */
>> +		if (apple_smc_read_u16(power->smc, SMC_KEY(AC-n), &vu16) >= 0) {
>> +			props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_NOW;
>> +			props[nprops++] = POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT;
>> +		}
> 
> we can do the same trick here assuming AC-n and AC-i are only present if
> ACPW is present.

See my comment above.

> 
>> +		power->ac_desc.properties = props;
>> +		power->ac_desc.num_properties = nprops;
>> +
>> +		psy_cfg.drv_data = power;
>> +		power->ac = devm_power_supply_register(dev, &power->ac_desc, &psy_cfg);
>> +		if (IS_ERR(power->ac)) {
>> +			dev_err_probe(dev, PTR_ERR(power->ac),
>> +				      "Failed to register AC adapter\n");
>> +			power->ac = NULL;
>> +		}
>> +	} else {
>> +		dev_dbg(dev, "No A/C adapter detected.\n");
> 
> same here
>> +	}
>> +
>> +	/* Final check: did we register anything? */
>> +	if (!power->batt && !power->ac)
>> +		return ret;
> 
> See my comment about the changed value of ret above
> 
>> +
>> +	power->nb.notifier_call = macsmc_power_event;
>> +	blocking_notifier_chain_register(&smc->event_handlers, &power->nb);
>> +
>> +	return 0;
>> +}
>> +
>> +static void macsmc_power_remove(struct platform_device *pdev)
>> +{
>> +	struct macsmc_power *power = dev_get_drvdata(&pdev->dev);
>> +
>> +	blocking_notifier_chain_unregister(&power->smc->event_handlers, &power->nb);
>> +}
>> +
>> +static const struct platform_device_id macsmc_power_id[] = {
>> +	{ "macsmc-power" },
>> +	{ /* sentinel */ }
>> +};
>> +MODULE_DEVICE_TABLE(platform, macsmc_power_id);
>> +
>> +static struct platform_driver macsmc_power_driver = {
>> +	.driver = {
>> +		.name = "macsmc-power",
>> +	},
>> +	.id_table = macsmc_power_id,
>> +	.probe = macsmc_power_probe,
>> +	.remove = macsmc_power_remove,
>> +};
>> +module_platform_driver(macsmc_power_driver);
>> +
>> +MODULE_LICENSE("Dual MIT/GPL");
>> +MODULE_DESCRIPTION("Apple SMC battery and power management driver");
>> +MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
>> +MODULE_AUTHOR("Michael Reeves <michael.reeves077@gmail.com>");
>>
>> -- 
>> 2.51.2
> 
> Janne
> 

Re: [PATCH v3 1/2] power: supply: Add macsmc-power driver for Apple Silicon

[Janne Grunau]

On Sun, Jan 18, 2026 at 08:19:38PM +0800, Nick Chan wrote:
> 
> 
> On 17/1/2026 20:26, Janne Grunau wrote:
> > On Thu, Jan 15, 2026 at 06:08:15PM +1100, Michael Reeves via B4 Relay wrote:
> >> From: Michael Reeves <michael.reeves077@gmail.com>
> > 
> > I think the driver is overall similar to the downstream AsahiLinux
> > driver so please keep Hector as author.
> > 
> >> This driver provides battery and AC status monitoring for Apple Silicon
> >> Macs via the SMC (System Management Controller). It supports
> >> reporting capacity, voltage, current, and charging status.
> >>
> >> Co-developed-by: Hector Martin <marcan@marcan.st>
> >> Signed-off-by: Hector Martin <marcan@marcan.st>
> > 
> > The downstream driver a quite a few more Co-developed-by:/Sobs. When I
> > squashed the commits I decided to err on the safe side and included
> > commit authors from incremental patches as Co-developed-by: Why did you
> > drop those?
> > 
> >> Reviewed-by: Neal Gompa <neal@gompa.dev>
> >> Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
> >> ---
> >>  MAINTAINERS                         |   1 +
> >>  drivers/power/supply/Kconfig        |  11 +
> >>  drivers/power/supply/Makefile       |   1 +
> >>  drivers/power/supply/macsmc-power.c | 834 ++++++++++++++++++++++++++++++++++++
> >>  4 files changed, 847 insertions(+)
> >>
> >> diff --git a/drivers/power/supply/macsmc-power.c b/drivers/power/supply/macsmc-power.c
> >> new file mode 100644
> >> index 000000000000..9b3faefe7a45
> >> --- /dev/null
> >> +++ b/drivers/power/supply/macsmc-power.c
> >> @@ -0,0 +1,834 @@

...

> >> +static int macsmc_power_probe(struct platform_device *pdev)
> >> +{
> >> +	struct device *dev = &pdev->dev;
> >> +	struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
> >> +	struct power_supply_config psy_cfg = {};
> >> +	struct macsmc_power *power;
> >> +	bool has_battery = false;
> >> +	bool has_ac_adapter = false;
> >> +	int ret = -ENODEV;
> >> +	bool flag;
> >> +	u16 vu16;
> >> +	u32 val32;
> >> +	enum power_supply_property *props;
> >> +	size_t nprops;
> >> +
> >> +	if (!smc)
> >> +		return -ENODEV;
> >> +
> >> +	power = devm_kzalloc(dev, sizeof(*power), GFP_KERNEL);
> >> +	if (!power)
> >> +		return -ENOMEM;
> >> +
> >> +	power->dev = dev;
> >> +	power->smc = smc;
> >> +	dev_set_drvdata(dev, power);
> >> +
> >> +	INIT_WORK(&power->critical_work, macsmc_power_critical_work);
> >> +	ret = devm_work_autocancel(dev, &power->critical_work, macsmc_power_critical_work);
> >> +	if (ret)
> >> +		return ret;
> >> +
> >> +	/*
> >> +	 * Check for battery presence.
> >> +	 * B0AV is a fundamental key.
> >> +	 */
> >> +	if (apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16) == 0 &&
> >> +	    macsmc_battery_get_status(power) > POWER_SUPPLY_STATUS_UNKNOWN)
> >> +		has_battery = true;
> >> +
> >> +	/*
> >> +	 * Check for AC adapter presence.
> >> +	 * CHIS is a fundamental key.
> >> +	 */
> >> +	if (apple_smc_key_exists(smc, SMC_KEY(CHIS)))
> >> +		has_ac_adapter = true;
> >> +
> > 
> > I think a short circuit check for !(has_battery || has_ac_adapter) would
> > make sense here. The setup code for props is quite long. It should
> > return -ENODEV. ret is not -ENODEV. anymore since it was overwritten
> > with the return value of devm_work_autocancel()
> > 
> >> +	if (has_battery) {
> >> +		power->batt_desc = macsmc_battery_desc_template;
> >> +		props = devm_kcalloc(dev, MACSMC_MAX_BATT_PROPS,
> >> +				     sizeof(enum power_supply_property),
> >> +				     GFP_KERNEL);
> > 
> > I don't like the dynamic allocation for the props. I think we can
> > currently get way with static property arrays and so we should do that.
> > See my comments below
> 
> Dynamic allocation is needed to properly add support pre-M1 support,
> as the SMCs in them misses a few keys, yet in iOS 16 the charge limit
> (CHWA) keys are added. In a similar way, there really is no sane way
> to add any new properties for M1/M2/M3 with static allocation. So I
> would prefer if dynamic allocation is kept.

ack, I wasn't really thinking beyond the code in front of me. Let's go
with dynamic allocations. A check that nprops doesn't exceed
MACSMC_MAX_BATT_PROPS should be added then.

Janne

Re: [PATCH v3 1/2] power: supply: Add macsmc-power driver for Apple Silicon

[Michael Reeves]

Hi Janne,

Thank you for the feedback.

On Sat, Jan 17, 2026 at 11:26 PM Janne Grunau <j@jannau.net> wrote:
>
> On Thu, Jan 15, 2026 at 06:08:15PM +1100, Michael Reeves via B4 Relay wrote:
> > From: Michael Reeves <michael.reeves077@gmail.com>
>
> I think the driver is overall similar to the downstream AsahiLinux
> driver so please keep Hector as author.
>
Will change in v4!
> > This driver provides battery and AC status monitoring for Apple Silicon
> > Macs via the SMC (System Management Controller). It supports
> > reporting capacity, voltage, current, and charging status.
> >
> > Co-developed-by: Hector Martin <marcan@marcan.st>
> > Signed-off-by: Hector Martin <marcan@marcan.st>
>
> The downstream driver a quite a few more Co-developed-by:/Sobs. When I
> squashed the commits I decided to err on the safe side and included
> commit authors from incremental patches as Co-developed-by: Why did you
> drop those?
Oh sorry, the UI just displayed marcan because, as you said, the
commit was squashed to a single From: marcan commit in the main
 upstream branch.

I see them now on closer inspection and will add SOBs/CDBs in v4,
except for the contributor who added unconditional available charge behaviour
reporting, because that code is not in the refactored upstream driver I've made
here - it's different and conditional now. Unless you think it's
fairer and safer to
also include that?
[...]
> > +
> > +struct macsmc_power {
> > +     struct device *dev;
> > +     struct apple_smc *smc;
> > +
> > +     struct power_supply_desc ac_desc;
> > +     struct power_supply_desc batt_desc;
> > +
> > +     struct power_supply *batt;
> > +     struct power_supply *ac;
> > +
> > +     char model_name[MAX_STRING_LENGTH];
> > +     char serial_number[MAX_STRING_LENGTH];
> > +     char mfg_date[MAX_STRING_LENGTH];
> > +
> > +     bool has_chwa;
> > +     bool has_chls;
> > +     bool has_ch0i;
> > +     bool has_ch0c;
> > +     bool has_chte;
>
> I think comments what these keys do and in which firmware version the
> appeared or vanished would be helpful here. I can Help with digging
> through the history.
>
Will add in v4, thank you for the suggestion. WIll let you know on IRC
if any help is needed but can see the full history now.
> > +
> > +     u8 num_cells;
> > +     int nominal_voltage_mv;
> > +
> > +     struct notifier_block nb;
> > +     struct work_struct critical_work;
> > +     bool shutdown_started;
> > +};
> > +
> > +static int macsmc_battery_get_status(struct macsmc_power *power)
> > +{
> > +     u64 nocharge_flags;
> > +     u32 nopower_flags;
> > +     u16 ac_current;
> > +     int charge_limit = 0;
> > +     bool limited = false;
> > +     bool flag;
> > +     int ret;
> > +
> > +     /*
> > +      * Fallbacks exist for keys that may disappear in future hardware.
> > +      * CHCE/CHCC/BSFC/CHSC are considered fundamental; absence is an error.
> > +      */
>
> Why did you rewrite this (and many other) comments? I don't think this
> is an improvement over the comment in the downstream driver.
>
I tried to make comments clearer / more concise where needed / make more sense
for upstream, so that it would be easier to understand for a wider audience, if
there's any changes you don't like, please let me know and I can restore the
original comment if that would make more sense.
[...]
> > +
> > +static int macsmc_battery_set_charge_behaviour(struct macsmc_power *power, int val)
> > +{
> > +     int ret;
> > +
> > +     /* First, reset all inhibitors to a known-good 'auto' state */
>
> why? I wouldn't expect this function to make any if `val` is not
> supported. If has_ch0i is not true
> POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE will reset inhibit charge
> and return -EOPNOTSUPP which is unexpected.
> Resetting the values first and then change them to the actual desired
> values doesn't make much sense either.
> Yes, it's a little annoying to make the same calls in multiple cases of
> the switch statement but you could move the `power->has_*` checks and
> the smc writes to a single line.
>
I'll refactor this to handle the specific writes within each switch
case for v4, thank you for the pickup!
> > +     if (power->has_ch0i) {
> > +             ret = apple_smc_write_u8(power->smc, SMC_KEY(CH0I), 0);
> > +             if (ret)
> > +                     return ret;
> > +     }
> > +
> > +     if (power->has_chte) {
> > +             ret = apple_smc_write_u32(power->smc, SMC_KEY(CHTE), 0);
> > +             if (ret)
> > +                     return ret;
> > +     } else if (power->has_ch0c) {
> > +             ret = apple_smc_write_u8(power->smc, SMC_KEY(CH0C), 0);
> > +             if (ret)
> > +                     return ret;
> > +     }
> > +
> > +     switch (val) {
> > +     case POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO:
> > +             return 0;
> > +
> > +     case POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE:
> > +             if (power->has_chte)
> > +                     return apple_smc_write_u32(power->smc, SMC_KEY(CHTE), 1);
> > +             else if (power->has_ch0c)
> > +                     return apple_smc_write_u8(power->smc, SMC_KEY(CH0C), 1);
> > +             else
> > +                     return -EOPNOTSUPP;
> > +             break;
> > +
> > +     case POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE:
> > +             if (!power->has_ch0i)
> > +                     return -EOPNOTSUPP;
> > +             return apple_smc_write_u8(power->smc, SMC_KEY(CH0I), 1);
> > +
> > +     default:
> > +             return -EINVAL;
> > +     }
> > +}
> > +
> > +static int macsmc_battery_get_date(const char *s, int *out)
> > +{
> > +     if (!isdigit(s[0]) || !isdigit(s[1]))
> > +             return -EOPNOTSUPP;
> > +
> > +     *out = (s[0] - '0') * 10 + s[1] - '0';
> > +     return 0;
> > +}
> > +
> > +static int macsmc_battery_get_capacity_level(struct macsmc_power *power)
> > +{
> > +     bool flag;
> > +     u32 val;
> > +     int ret;
> > +
> > +     /* Check for emergency shutdown condition */
> > +     if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val) >= 0 && val)
> > +             return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
> > +
> > +     /* Check AC status for whether we could boot in this state */
> > +     if (apple_smc_read_u32(power->smc, SMC_KEY(ACSt), &val) >= 0) {
> > +             if (!(val & ACSt_CAN_BOOT_IBOOT))
> > +                     return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL;
> > +
> > +             if (!(val & ACSt_CAN_BOOT_AP))
> > +                     return POWER_SUPPLY_CAPACITY_LEVEL_LOW;
> > +     }
> > +
> > +     ret = apple_smc_read_flag(power->smc, SMC_KEY(BSFC), &flag);
>
> the comment in the downstream driver what the flag is helpful
>
Will add back (maybe with clarification/cleanup) in v4, thank you!

> > +     .set_property           = macsmc_battery_set_property,
> > +     .property_is_writeable  = macsmc_battery_property_is_writeable,
> > +};
> > +
> > +static int macsmc_ac_get_property(struct power_supply *psy,
> > +                               enum power_supply_property psp,
> > +                               union power_supply_propval *val)
> > +{
> > +     struct macsmc_power *power = power_supply_get_drvdata(psy);
> > +     int ret = 0;
> > +     u16 vu16;
> > +     u32 vu32;
> > +
> > +     switch (psp) {
> > +     case POWER_SUPPLY_PROP_ONLINE:
> > +             ret = apple_smc_read_u32(power->smc, SMC_KEY(CHIS), &vu32);
> > +             val->intval = !!vu32;
> > +             break;
> > +     case POWER_SUPPLY_PROP_VOLTAGE_NOW:
> > +             ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-n), &vu16);
> > +             val->intval = vu16 * 1000;
> > +             break;
> > +     case POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT:
> > +             ret = apple_smc_read_u16(power->smc, SMC_KEY(AC-i), &vu16);
> > +             val->intval = vu16 * 1000;
> > +             break;
> > +     case POWER_SUPPLY_PROP_INPUT_POWER_LIMIT:
> > +             ret = apple_smc_read_u32(power->smc, SMC_KEY(ACPW), &vu32);
> > +             val->intval = vu32 * 1000;
> > +             break;
> > +     default:
> > +             return -EINVAL;
> > +     }
> > +
> > +     return ret;
> > +}
> > +
> > +static const struct power_supply_desc macsmc_ac_desc_template = {
> > +     .name                   = "macsmc-ac",
> > +     .type                   = POWER_SUPPLY_TYPE_MAINS,
> > +     .get_property           = macsmc_ac_get_property,
> > +};
> > +
> > +static void macsmc_power_critical_work(struct work_struct *wrk)
> > +{
> > +     struct macsmc_power *power = container_of(wrk, struct macsmc_power, critical_work);
> > +     u16 bitv, b0av;
> > +     u32 bcf0;
> > +
> > +     if (!power->batt)
> > +             return;
> > +
> > +     /*
> > +      * EMERGENCY: Check voltage vs design minimum.
> > +      * If we are below BITV, the battery is physically exhausted.
> > +      * We must shut down NOW to protect the filesystem.
> > +      */
> > +     if (apple_smc_read_u16(power->smc, SMC_KEY(BITV), &bitv) >= 0 &&
> > +         apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &b0av) >= 0 &&
> > +         b0av < bitv) {
> > +             dev_emerg(power->dev,
> > +                       "Battery voltage (%d mV) below design minimum (%d mV)! Emergency shutdown.\n",
> > +                       b0av, bitv);
> > +             kernel_power_off();
> > +             return;
>
> I don't think we should return here. kernel_power_off() may do
> nothing in which case the orderly_poweroff(true) might save data.
> I would protect it as well via power->shutdown_started like in the
> downstream driver to avoid calling kernel_power_off() once per second
> until the battery dies or the system shutsdown.
>
Sounds good, will fix in v4. Note that the way orderly_poweroff(true) saves
data (if userspace fails to respond) is an emergency_sync() before
kernel_power_off() so we could also just add emergency_sync() to this
code path to achieve the same effect.

Re protection, it would probably be useful to, if we go down the route
of removing the return, have 2 separate flags for orderly vs non-orderly
shutdown started so we can "upgrade" a shutdown where needed as the comment
I added below clarifies.
> > +     }
> > +
> > +     /*
> > +      * Avoid duplicate attempts at orderly shutdown.
> > +      * Voltage check is above this as we may want to
> > +      * "upgrade" an orderly shutdown to a critical power
> > +      * off if voltage drops.
> > +      */
> > +     if (power->shutdown_started || system_state > SYSTEM_RUNNING)
> > +             return;
> > +
> > +     /*
> > +      * Check if SMC flagged the battery as empty.
> > +      * We trigger a graceful shutdown to let the OS save data.
> > +      */
> > +     if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &bcf0) == 0 && bcf0 != 0) {
> > +             power->shutdown_started = true;
> > +             dev_crit(power->dev, "Battery critical (empty flag set). Triggering orderly shutdown.\n");
> > +             orderly_poweroff(true);
> > +     }
> > +}
> > +
[...]
> > +static int macsmc_power_probe(struct platform_device *pdev)
> > +{
> > +     struct device *dev = &pdev->dev;
> > +     struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
> > +     struct power_supply_config psy_cfg = {};
> > +     struct macsmc_power *power;
> > +     bool has_battery = false;
> > +     bool has_ac_adapter = false;
> > +     int ret = -ENODEV;
> > +     bool flag;
> > +     u16 vu16;
> > +     u32 val32;
> > +     enum power_supply_property *props;
> > +     size_t nprops;
> > +
> > +     if (!smc)
> > +             return -ENODEV;
> > +
> > +     power = devm_kzalloc(dev, sizeof(*power), GFP_KERNEL);
> > +     if (!power)
> > +             return -ENOMEM;
> > +
> > +     power->dev = dev;
> > +     power->smc = smc;
> > +     dev_set_drvdata(dev, power);
> > +
> > +     INIT_WORK(&power->critical_work, macsmc_power_critical_work);
> > +     ret = devm_work_autocancel(dev, &power->critical_work, macsmc_power_critical_work);
> > +     if (ret)
> > +             return ret;
> > +
> > +     /*
> > +      * Check for battery presence.
> > +      * B0AV is a fundamental key.
> > +      */
> > +     if (apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16) == 0 &&
> > +         macsmc_battery_get_status(power) > POWER_SUPPLY_STATUS_UNKNOWN)
> > +             has_battery = true;
> > +
> > +     /*
> > +      * Check for AC adapter presence.
> > +      * CHIS is a fundamental key.
> > +      */
> > +     if (apple_smc_key_exists(smc, SMC_KEY(CHIS)))
> > +             has_ac_adapter = true;
> > +
>
> I think a short circuit check for !(has_battery || has_ac_adapter) would
> make sense here. The setup code for props is quite long. It should
> return -ENODEV. ret is not -ENODEV. anymore since it was overwritten
> with the return value of devm_work_autocancel()
>
Thank you for the pickup, will fix in v4.
> > +     if (has_battery) {
> > +             power->batt_desc = macsmc_battery_desc_template;
> > +             props = devm_kcalloc(dev, MACSMC_MAX_BATT_PROPS,
> > +                                  sizeof(enum power_supply_property),
> > +                                  GFP_KERNEL);
>
> I don't like the dynamic allocation for the props. I think we can
> currently get way with static property arrays and so we should do that.
> See my comments below
>
I think dynamic allocation is useful for backward and forward
compatibility in future (while I have been writing this Draft, Nick
Chan has sent a reply echoing this
from a pre-M1 bringup perspective), and is also cleaner / less hacky,
so would also prefer if it's kept, but happy to change to static if that's the
consensus that emerges.
> > +             if (!props)
> > +                     return -ENOMEM;
> > +
> > +             nprops = 0;
> > +
> > +             /* Fundamental properties */
> > +             props[nprops++] = POWER_SUPPLY_PROP_STATUS;
> > +             props[nprops++] = POWER_SUPPLY_PROP_PRESENT;
> > +             props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_NOW;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CURRENT_NOW;
> > +             props[nprops++] = POWER_SUPPLY_PROP_POWER_NOW;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CAPACITY;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CAPACITY_LEVEL;
> > +             props[nprops++] = POWER_SUPPLY_PROP_TEMP;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CYCLE_COUNT;
> > +             props[nprops++] = POWER_SUPPLY_PROP_HEALTH;
> > +             props[nprops++] = POWER_SUPPLY_PROP_SCOPE;
> > +             props[nprops++] = POWER_SUPPLY_PROP_MODEL_NAME;
> > +             props[nprops++] = POWER_SUPPLY_PROP_SERIAL_NUMBER;
> > +             props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_YEAR;
> > +             props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_MONTH;
> > +             props[nprops++] = POWER_SUPPLY_PROP_MANUFACTURE_DAY;
> > +
> > +             /* Extended properties usually present */
> > +             props[nprops++] = POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW;
> > +             props[nprops++] = POWER_SUPPLY_PROP_TIME_TO_FULL_NOW;
> > +             props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN;
> > +             props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN;
> > +             props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MIN;
> > +             props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_MAX;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CHARGE_TERM_CURRENT;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CONSTANT_CHARGE_CURRENT_MAX;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CONSTANT_CHARGE_VOLTAGE;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CHARGE_FULL;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CHARGE_NOW;
> > +             props[nprops++] = POWER_SUPPLY_PROP_ENERGY_FULL_DESIGN;
> > +             props[nprops++] = POWER_SUPPLY_PROP_ENERGY_FULL;
> > +             props[nprops++] = POWER_SUPPLY_PROP_ENERGY_NOW;
> > +             props[nprops++] = POWER_SUPPLY_PROP_CHARGE_COUNTER;
> > +
> > +             /* Detect features based on key availability */
> > +             if (apple_smc_key_exists(smc, SMC_KEY(CHTE)))
> > +                     power->has_chte = true;
> > +             if (apple_smc_key_exists(smc, SMC_KEY(CH0C)))
> > +                     power->has_ch0c = true;
> > +             if (apple_smc_key_exists(smc, SMC_KEY(CH0I)))
> > +                     power->has_ch0i = true;
> > +
> > +             /* Reset "Optimised Battery Charging" flags to default state */
> > +             if (power->has_chte)
> > +                     apple_smc_write_u32(smc, SMC_KEY(CHTE), 0);
> > +             else if (power->has_ch0c)
> > +                     apple_smc_write_u8(smc, SMC_KEY(CH0C), 0);
> > +
> > +             if (power->has_ch0i)
> > +                     apple_smc_write_u8(smc, SMC_KEY(CH0I), 0);
> > +
> > +             apple_smc_write_u8(smc, SMC_KEY(CH0K), 0);
> > +             apple_smc_write_u8(smc, SMC_KEY(CH0B), 0);
> > +
> > +             /* Configure charge behaviour if supported */
> > +             if (power->has_ch0i || power->has_ch0c || power->has_chte) {
> > +                     props[nprops++] = POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR;
>
> This is the only dynamic battery prop. With a static array we can simply
> put it at the end of the array and set batt_desc.num_properties to array
> size - 1 if none of the keys are available.
>
See above.
> > +
> > +                     power->batt_desc.charge_behaviours =
> > +                             BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO);
> > +
> > +                     if (power->has_ch0i)
> > +                             power->batt_desc.charge_behaviours |=
> > +                                     BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE);
> > +
> > +                     if (power->has_chte || power->has_ch0c)
> > +                             power->batt_desc.charge_behaviours |=
> > +                                     BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE);
> > +             }
> > +
> > +             /* Detect charge limit method (CHWA vs CHLS) */
> > +             if (apple_smc_read_flag(power->smc, SMC_KEY(CHWA), &flag) == 0)
> > +                     power->has_chwa = true;
> > +             else if (apple_smc_read_u16(power->smc, SMC_KEY(CHLS), &vu16) >= 0)
> > +                     power->has_chls = true;
> > +
> > +             power->batt_desc.properties = props;
> > +             power->batt_desc.num_properties = nprops;
> > +
> > +             /* Fetch identity strings */
> > +             apple_smc_read(smc, SMC_KEY(BMDN), power->model_name,
> > +                            sizeof(power->model_name) - 1);
> > +             apple_smc_read(smc, SMC_KEY(BMSN), power->serial_number,
> > +                            sizeof(power->serial_number) - 1);
> > +             apple_smc_read(smc, SMC_KEY(BMDT), power->mfg_date,
> > +                            sizeof(power->mfg_date) - 1);
> > +
> > +             apple_smc_read_u8(power->smc, SMC_KEY(BNCB), &power->num_cells);
> > +             power->nominal_voltage_mv = MACSMC_NOMINAL_CELL_VOLTAGE_MV * power->num_cells;
> > +
> > +             /* Enable critical shutdown notifications by reading status once */
> > +             apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val32);
> > +
> > +             psy_cfg.drv_data = power;
> > +             power->batt = devm_power_supply_register(dev, &power->batt_desc, &psy_cfg);
> > +             if (IS_ERR(power->batt)) {
> > +                     dev_err_probe(dev, PTR_ERR(power->batt),
> > +                                   "Failed to register battery\n");
> > +                     /* Don't return failure yet; try AC registration first */
> > +                     power->batt = NULL;
> > +             }
> > +     } else {
> > +             dev_dbg(dev, "No battery detected.\n");
>
> I would drop this
>
Will do in v4, thank you!
> > +     }
> > +
> > +     if (has_ac_adapter) {
> > +             power->ac_desc = macsmc_ac_desc_template;
> > +             props = devm_kcalloc(dev, MACSMC_MAX_AC_PROPS,
> > +                                  sizeof(enum power_supply_property),
> > +                                  GFP_KERNEL);
> > +             if (!props)
> > +                     return -ENOMEM;
> > +
> > +             nprops = 0;
> > +
> > +             /* Online status is fundamental */
> > +             props[nprops++] = POWER_SUPPLY_PROP_ONLINE;
> > +
> > +             /* Input power limits are usually available */
> > +             if (apple_smc_key_exists(power->smc, SMC_KEY(ACPW)))
> > +                     props[nprops++] = POWER_SUPPLY_PROP_INPUT_POWER_LIMIT;
> > +
> > +             /* macOS 15.4+ firmware dropped legacy AC keys (AC-n, AC-i) */
> > +             if (apple_smc_read_u16(power->smc, SMC_KEY(AC-n), &vu16) >= 0) {
> > +                     props[nprops++] = POWER_SUPPLY_PROP_VOLTAGE_NOW;
> > +                     props[nprops++] = POWER_SUPPLY_PROP_INPUT_CURRENT_LIMIT;
> > +             }
>
> we can do the same trick here assuming AC-n and AC-i are only present if
> ACPW is present.
>
See above comment.
> > +             power->ac_desc.properties = props;
> > +             power->ac_desc.num_properties = nprops;
> > +
> > +             psy_cfg.drv_data = power;
> > +             power->ac = devm_power_supply_register(dev, &power->ac_desc, &psy_cfg);
> > +             if (IS_ERR(power->ac)) {
> > +                     dev_err_probe(dev, PTR_ERR(power->ac),
> > +                                   "Failed to register AC adapter\n");
> > +                     power->ac = NULL;
> > +             }
> > +     } else {
> > +             dev_dbg(dev, "No A/C adapter detected.\n");
>
> same here
Will drop, thanks!
> > +     }
> > +
> > +     /* Final check: did we register anything? */
> > +     if (!power->batt && !power->ac)
> > +             return ret;
>
> See my comment about the changed value of ret above
>
Yes, will fix in v4, thank you again for the pickup!
[...]
Thank you so much for your time!

Best regards,
Michael

On Sun, Jan 18, 2026 at 11:49 PM Janne Grunau <j@jannau.net> wrote:
>
> On Sun, Jan 18, 2026 at 08:19:38PM +0800, Nick Chan wrote:
> >
> >
> > On 17/1/2026 20:26, Janne Grunau wrote:
> > > On Thu, Jan 15, 2026 at 06:08:15PM +1100, Michael Reeves via B4 Relay wrote:
> > >> From: Michael Reeves <michael.reeves077@gmail.com>
> > >
> > > I think the driver is overall similar to the downstream AsahiLinux
> > > driver so please keep Hector as author.
> > >
> > >> This driver provides battery and AC status monitoring for Apple Silicon
> > >> Macs via the SMC (System Management Controller). It supports
> > >> reporting capacity, voltage, current, and charging status.
> > >>
> > >> Co-developed-by: Hector Martin <marcan@marcan.st>
> > >> Signed-off-by: Hector Martin <marcan@marcan.st>
> > >
> > > The downstream driver a quite a few more Co-developed-by:/Sobs. When I
> > > squashed the commits I decided to err on the safe side and included
> > > commit authors from incremental patches as Co-developed-by: Why did you
> > > drop those?
> > >
> > >> Reviewed-by: Neal Gompa <neal@gompa.dev>
> > >> Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
> > >> ---
> > >>  MAINTAINERS                         |   1 +
> > >>  drivers/power/supply/Kconfig        |  11 +
> > >>  drivers/power/supply/Makefile       |   1 +
> > >>  drivers/power/supply/macsmc-power.c | 834 ++++++++++++++++++++++++++++++++++++
> > >>  4 files changed, 847 insertions(+)
> > >>
> > >> diff --git a/drivers/power/supply/macsmc-power.c b/drivers/power/supply/macsmc-power.c
> > >> new file mode 100644
> > >> index 000000000000..9b3faefe7a45
> > >> --- /dev/null
> > >> +++ b/drivers/power/supply/macsmc-power.c
> > >> @@ -0,0 +1,834 @@
>
> ...
>
> > >> +static int macsmc_power_probe(struct platform_device *pdev)
> > >> +{
> > >> +  struct device *dev = &pdev->dev;
> > >> +  struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent);
> > >> +  struct power_supply_config psy_cfg = {};
> > >> +  struct macsmc_power *power;
> > >> +  bool has_battery = false;
> > >> +  bool has_ac_adapter = false;
> > >> +  int ret = -ENODEV;
> > >> +  bool flag;
> > >> +  u16 vu16;
> > >> +  u32 val32;
> > >> +  enum power_supply_property *props;
> > >> +  size_t nprops;
> > >> +
> > >> +  if (!smc)
> > >> +          return -ENODEV;
> > >> +
> > >> +  power = devm_kzalloc(dev, sizeof(*power), GFP_KERNEL);
> > >> +  if (!power)
> > >> +          return -ENOMEM;
> > >> +
> > >> +  power->dev = dev;
> > >> +  power->smc = smc;
> > >> +  dev_set_drvdata(dev, power);
> > >> +
> > >> +  INIT_WORK(&power->critical_work, macsmc_power_critical_work);
> > >> +  ret = devm_work_autocancel(dev, &power->critical_work, macsmc_power_critical_work);
> > >> +  if (ret)
> > >> +          return ret;
> > >> +
> > >> +  /*
> > >> +   * Check for battery presence.
> > >> +   * B0AV is a fundamental key.
> > >> +   */
> > >> +  if (apple_smc_read_u16(power->smc, SMC_KEY(B0AV), &vu16) == 0 &&
> > >> +      macsmc_battery_get_status(power) > POWER_SUPPLY_STATUS_UNKNOWN)
> > >> +          has_battery = true;
> > >> +
> > >> +  /*
> > >> +   * Check for AC adapter presence.
> > >> +   * CHIS is a fundamental key.
> > >> +   */
> > >> +  if (apple_smc_key_exists(smc, SMC_KEY(CHIS)))
> > >> +          has_ac_adapter = true;
> > >> +
> > >
> > > I think a short circuit check for !(has_battery || has_ac_adapter) would
> > > make sense here. The setup code for props is quite long. It should
> > > return -ENODEV. ret is not -ENODEV. anymore since it was overwritten
> > > with the return value of devm_work_autocancel()
> > >
> > >> +  if (has_battery) {
> > >> +          power->batt_desc = macsmc_battery_desc_template;
> > >> +          props = devm_kcalloc(dev, MACSMC_MAX_BATT_PROPS,
> > >> +                               sizeof(enum power_supply_property),
> > >> +                               GFP_KERNEL);
> > >
> > > I don't like the dynamic allocation for the props. I think we can
> > > currently get way with static property arrays and so we should do that.
> > > See my comments below
> >
> > Dynamic allocation is needed to properly add support pre-M1 support,
> > as the SMCs in them misses a few keys, yet in iOS 16 the charge limit
> > (CHWA) keys are added. In a similar way, there really is no sane way
> > to add any new properties for M1/M2/M3 with static allocation. So I
> > would prefer if dynamic allocation is kept.
>
> ack, I wasn't really thinking beyond the code in front of me. Let's go
> with dynamic allocations. A check that nprops doesn't exceed
> MACSMC_MAX_BATT_PROPS should be added then.
>
> Janne

[PATCH v3 2/2] mfd: macsmc: Wire up Apple SMC power driver

[Michael Reeves via B4 Relay]

From: Michael Reeves <michael.reeves077@gmail.com>

Add the cell for the macsmc-power driver so it is probed by the
MFD core.

Co-developed-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
---
 drivers/mfd/macsmc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/mfd/macsmc.c b/drivers/mfd/macsmc.c
index 1b7e7b3e785f..358feec2d088 100644
--- a/drivers/mfd/macsmc.c
+++ b/drivers/mfd/macsmc.c
@@ -46,6 +46,7 @@
 
 static const struct mfd_cell apple_smc_devs[] = {
 	MFD_CELL_NAME("macsmc-input"),
+	MFD_CELL_NAME("macsmc-power"),
 	MFD_CELL_OF("macsmc-gpio", NULL, NULL, 0, 0, "apple,smc-gpio"),
 	MFD_CELL_OF("macsmc-hwmon", NULL, NULL, 0, 0, "apple,smc-hwmon"),
 	MFD_CELL_OF("macsmc-reboot", NULL, NULL, 0, 0, "apple,smc-reboot"),

-- 
2.51.2

Re: [PATCH v3 2/2] mfd: macsmc: Wire up Apple SMC power driver

[Janne Grunau]

On Thu, Jan 15, 2026 at 06:08:16PM +1100, Michael Reeves via B4 Relay wrote:
> From: Michael Reeves <michael.reeves077@gmail.com>
> 
> Add the cell for the macsmc-power driver so it is probed by the
> MFD core.
> 
> Co-developed-by: Hector Martin <marcan@marcan.st>
> Signed-off-by: Hector Martin <marcan@marcan.st>

Co-developed-by: for a single line change as simple as this is silly.
Please just keep Hector as author and just add your SOB

> Reviewed-by: Neal Gompa <neal@gompa.dev>
> Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
> ---
>  drivers/mfd/macsmc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/mfd/macsmc.c b/drivers/mfd/macsmc.c
> index 1b7e7b3e785f..358feec2d088 100644
> --- a/drivers/mfd/macsmc.c
> +++ b/drivers/mfd/macsmc.c
> @@ -46,6 +46,7 @@
>  
>  static const struct mfd_cell apple_smc_devs[] = {
>  	MFD_CELL_NAME("macsmc-input"),
> +	MFD_CELL_NAME("macsmc-power"),
>  	MFD_CELL_OF("macsmc-gpio", NULL, NULL, 0, 0, "apple,smc-gpio"),
>  	MFD_CELL_OF("macsmc-hwmon", NULL, NULL, 0, 0, "apple,smc-hwmon"),
>  	MFD_CELL_OF("macsmc-reboot", NULL, NULL, 0, 0, "apple,smc-reboot"),

This patch does not apply on top of v6.19-rc1. The base-commit helpfully
provided by b4 does not exists in my tree. I assume it's either a mfd or
linux-next commit? Please note the branch/tag this series applies to in
the cover letter if it is not the most recent -rc1 from Linus

Janne

Re: [PATCH v3 2/2] mfd: macsmc: Wire up Apple SMC power driver

[Michael Reeves]

Hi Janne,

Thank you again for your feedback!

On Sat, Jan 17, 2026 at 11:32 PM Janne Grunau <j@jannau.net> wrote:
>
> On Thu, Jan 15, 2026 at 06:08:16PM +1100, Michael Reeves via B4 Relay wrote:
> > From: Michael Reeves <michael.reeves077@gmail.com>
> >
> > Add the cell for the macsmc-power driver so it is probed by the
> > MFD core.
> >
> > Co-developed-by: Hector Martin <marcan@marcan.st>
> > Signed-off-by: Hector Martin <marcan@marcan.st>
>
> Co-developed-by: for a single line change as simple as this is silly.
> Please just keep Hector as author and just add your SOB
>
Will fix in v4, thanks for pointing it out!
> > Reviewed-by: Neal Gompa <neal@gompa.dev>
> > Signed-off-by: Michael Reeves <michael.reeves077@gmail.com>
> > ---
> >  drivers/mfd/macsmc.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/mfd/macsmc.c b/drivers/mfd/macsmc.c
> > index 1b7e7b3e785f..358feec2d088 100644
> > --- a/drivers/mfd/macsmc.c
> > +++ b/drivers/mfd/macsmc.c
> > @@ -46,6 +46,7 @@
> >
> >  static const struct mfd_cell apple_smc_devs[] = {
> >       MFD_CELL_NAME("macsmc-input"),
> > +     MFD_CELL_NAME("macsmc-power"),
> >       MFD_CELL_OF("macsmc-gpio", NULL, NULL, 0, 0, "apple,smc-gpio"),
> >       MFD_CELL_OF("macsmc-hwmon", NULL, NULL, 0, 0, "apple,smc-hwmon"),
> >       MFD_CELL_OF("macsmc-reboot", NULL, NULL, 0, 0, "apple,smc-reboot"),
>
> This patch does not apply on top of v6.19-rc1. The base-commit helpfully
> provided by b4 does not exists in my tree. I assume it's either a mfd or
> linux-next commit? Please note the branch/tag this series applies to in
> the cover letter if it is not the most recent -rc1 from Linus
>
It's based on-top of the latest linux-next, I will mention this in the
cover letter
body for v4 (i only put it in 'Changes in v3' for this one), thank you for the
pickup!
> Janne

Thank you again!

Best regards,
Michael