[RFC PATCH 06/14] leds: add support for macsmc kbl

[Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>]

Add a LED class driver to control the keyboard backlight.

This replaces the keyboard backlight support in applesmc.

Signed-off-by: Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
---
 drivers/leds/Kconfig       | 11 ++++++
 drivers/leds/Makefile      |  1 +
 drivers/leds/leds-macsmc.c | 69 ++++++++++++++++++++++++++++++++++++++
 drivers/mfd/macsmc-core.c  | 11 ++++++
 4 files changed, 92 insertions(+)
 create mode 100644 drivers/leds/leds-macsmc.c

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 7ec2c8d78..30cd64d41 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -729,6 +729,17 @@ config LEDS_ADP5520
 	  To compile this driver as a module, choose M here: the module will
 	  be called leds-adp5520.
 
+config LEDS_MACSMC
+	tristate "Keyboard Backlight support for Intel-Macs"
+	depends on LEDS_CLASS
+	depends on MACSMC_ACPI
+	help
+	  This option enables support for the Keyboard backlight in
+	  Intel-Macs using macsmc.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called leds-macsmc.
+
 config LEDS_MAX5970
 	tristate "LED Support for Maxim 5970"
 	depends on LEDS_CLASS
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 4d4b08915..7c38dbef4 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -12,6 +12,7 @@ obj-$(CONFIG_LEDS_KUNIT_TEST)		+= led-test.o
 obj-$(CONFIG_LEDS_88PM860X)		+= leds-88pm860x.o
 obj-$(CONFIG_LEDS_ACER_A500)		+= leds-acer-a500.o
 obj-$(CONFIG_LEDS_ADP5520)		+= leds-adp5520.o
+obj-$(CONFIG_LEDS_MACSMC)		+= leds-macsmc.o
 obj-$(CONFIG_LEDS_AN30259A)		+= leds-an30259a.o
 obj-$(CONFIG_LEDS_APU)			+= leds-apu.o
 obj-$(CONFIG_LEDS_ARIEL)		+= leds-ariel.o
diff --git a/drivers/leds/leds-macsmc.c b/drivers/leds/leds-macsmc.c
new file mode 100644
index 000000000..f38ef2113
--- /dev/null
+++ b/drivers/leds/leds-macsmc.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Apple SMC Keyboard backlight driver
+ *
+ * Copyright (C) 2026 Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
+ *
+ * Based on drivers/hwmon/applesmc.c
+ * Copyright (C) 2007 Nicolas Boichat <nicolas@boichat.ch>
+ * Copyright (C) 2010 Henrik Rydberg <rydberg@euromail.se>
+ *
+ */
+
+#include <linux/leds.h>
+#include <linux/mfd/macsmc.h>
+#include <linux/platform_device.h>
+
+struct macsmc_led {
+	struct led_classdev cdev;
+	struct apple_smc *smc;
+	u8 brightness;
+};
+
+static enum led_brightness macsmc_led_get_brightness(struct led_classdev *cdev)
+{
+	struct macsmc_led *drv = container_of(cdev, struct macsmc_led, cdev);
+
+	return drv->brightness;
+}
+
+static void macsmc_led_set_brightness(struct led_classdev *cdev, enum led_brightness value)
+{
+	struct macsmc_led *drv = container_of(cdev, struct macsmc_led, cdev);
+
+	drv->brightness = (u8) value;
+
+	apple_smc_write_u16(drv->smc, SMC_KEY(LKSB), drv->brightness);
+}
+
+static int macsmc_led_probe(struct platform_device *pdev)
+{
+	struct macsmc_led *drv;
+
+	drv = devm_kzalloc(&pdev->dev, sizeof(*drv), GFP_KERNEL);
+	if (!drv)
+		return -ENOMEM;
+
+	drv->smc = dev_get_drvdata(pdev->dev.parent);
+
+	drv->cdev.name = "macsmc-led";
+	drv->cdev.max_brightness = 255;
+	drv->cdev.brightness_get = macsmc_led_get_brightness;
+	drv->cdev.brightness_set = macsmc_led_set_brightness;
+	drv->cdev.dev = &pdev->dev;
+
+	return devm_led_classdev_register(&pdev->dev, &drv->cdev);
+}
+
+static struct platform_driver macsmc_led_driver = {
+	.probe = macsmc_led_probe,
+	.driver = {
+		.name = "macsmc-led",
+	},
+};
+module_platform_driver(macsmc_led_driver);
+
+MODULE_AUTHOR("Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>");
+MODULE_DESCRIPTION("LED keyboard backlight driver for Intel-macs using macsmc");
+MODULE_LICENSE("Dual MIT/GPL");
+MODULE_ALIAS("platform:macsmc-led");
diff --git a/drivers/mfd/macsmc-core.c b/drivers/mfd/macsmc-core.c
index 6567d2f1f..bc4200f57 100644
--- a/drivers/mfd/macsmc-core.c
+++ b/drivers/mfd/macsmc-core.c
@@ -33,6 +33,10 @@ static const struct mfd_cell apple_smc_acpi_common[] = {
 	MFD_CELL_NAME("macsmc-power"),
 };
 
+static const struct mfd_cell apple_smc_acpi_led[] = {
+	MFD_CELL_NAME("macsmc-led"),
+};
+
 static const struct mfd_cell apple_smc_acpi_light[] = {
 	MFD_CELL_NAME("macsmc-light"),
 };
@@ -179,6 +183,13 @@ int apple_smc_probe(struct device *dev, const struct apple_smc_backend_ops *ops,
 			if (ret < 0)
 				return ret;
 		}
+
+		if (apple_smc_key_exists(smc, SMC_KEY(LKSB))) {
+			ret = devm_mfd_add_devices(dev, -1, apple_smc_acpi_led,
+				ARRAY_SIZE(apple_smc_acpi_led), NULL, 0, NULL);
+			if (ret < 0)
+				return ret;
+		}
 	} else
 		ret = devm_mfd_add_devices(dev, -1, apple_smc_rtkit_devs,
 			ARRAY_SIZE(apple_smc_rtkit_devs), NULL, 0, NULL);
-- 
2.55.0