[PATCH v6 0/3] HID: generic: add LampArray support via hid-lamparray helper

[PATCH v6 0/3] HID: generic: add LampArray support via hid-lamparray helper

[Aaron Erhardt]

Add a new hid-lamparray helper module and integrate it with the hid-generic
driver.

While more complex lamparray handling should be done in userspace via hidraw,
providing a small module to add basic lamparray support makes it possible for
userspace software to interact with lamparrays by simply using well-known APIs
of the LED subsystem. One use-case would be to enable desktop environments to
support keyboard backlight control out of the box for HID lamparray devices
without having to implement the whole HID protocol themselves.

This patch is based on previous discussions:
https://lore.kernel.org/all/1fb08a74-62c7-4d0c-ba5d-648e23082dcb@tuxedocomputers.com/

The helper provides basic support for devices exposing a Lighting/LampArray
application collection (usage page 0x59) and registers a single-zone RGB LED
representation via the LED subsystem.

hid-generic now checks for LampArray support after hid_parse() and optionally
registers a lamparray instance. Failures in the helper do not abort device probe
to keep the driver logic otherwise unchanged.

LampArray resources are released on driver remove.

This commit was successfully tested on the Microsoft MacroPad reference
implementation (https://github.com/microsoft/RP2040MacropadHidSample 1d6c3ad)
and in combination with the tuxedo_nb04_wmi driver, albeit only fully functional
with a recent fix posted to the LKML
(https://lore.kernel.org/all/20260826081149.235487-2-aer@tuxedocomputers.com).

Others reported the driver to work on the Acer Predator PT14-52T and the ASUS
Prime B650-Plus, with the former requiring some patches on top of v5, which
should now be included in v6.

v6:
- Read attribute reports synchronously (by Cristian Mazotta)
- Raise log level of fatal probe errors (by Cristian Mazotta)
- Transfer control when use_leds_uapi changes (by Cristian Mazotta)
- Blank lamps across suspend and restore on resume (by Cristian Mazotta)
- Add quirk for devices that ignore intensities (reported by Armin Wolf)
- Better locking, fixing rare races in uapi registration
- Use scope guards for locking and allocations where possible
- Remove obsolete calls to led_mc_calc_color_components and
  hid_device_io_start/stop
- Updated and slightly improved documentation
v5:
- Proper hardware detection (no quirks necessary anymore)
- Add documentation for new sysfs knob
- Pass limits of the device to sysfs (intensities & brightness)
- More flexible Kconfig (use tristate)
- Improved locking
- Several memory leak and (de-)initialization fixes
- Don't read current color values from hardware (the HID spec does not
  offer this option)
- Remove redundant report dump functionality
v4:
- Restrict CONFIG_HID_LAMPARRAY to built-in configurations only to fix
  additional randconfig build errors
v3:
- Squash V1 and V2 into one patch
v2:
- Fix Kconfig to avoid build errors when LEDS_CLASS_MULTICOLOR is
  disabled

Aaron Erhardt (2):
  HID: lamparray: add new LampArray helper module
  HID: generic: add LampArray support via hid-lamparray helper

Cristian Mazzotta (1):
  HID: lamparray: blank lamps across suspend and restore on resume

 .../ABI/testing/sysfs-driver-hid-lamparray    |  15 +
 drivers/hid/Kconfig                           |  18 +
 drivers/hid/Makefile                          |   2 +
 drivers/hid/hid-generic.c                     |  70 +-
 drivers/hid/hid-lamparray.c                   | 907 ++++++++++++++++++
 include/linux/hid-lamparray.h                 | 117 +++
 6 files changed, 1128 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-hid-lamparray
 create mode 100644 drivers/hid/hid-lamparray.c
 create mode 100644 include/linux/hid-lamparray.h

-- 
2.43.0

[PATCH v6 1/3] HID: lamparray: add new LampArray helper module

[Aaron Erhardt]

Add a new hid-lamparray helper module that provides basic support for
devices exposing a Lighting/LampArray application collection (usage
page 0x59) and registers a single-zone RGB LED representation via the
LED subsystem.

The module can be used as a library in HID drivers to add support for
the HID LampArray protocol. While the API is quite basic as of now
it could be extended in the future.

Co-developed-by: Tim Guttzeit <tgu@tuxedocomputers.com>
Signed-off-by: Tim Guttzeit <tgu@tuxedocomputers.com>
Co-developed-by: Cristian Mazzotta <cmmazzo@icloud.com>
Signed-off-by: Cristian Mazzotta <cmmazzo@icloud.com>
Signed-off-by: Aaron Erhardt <aer@tuxedocomputers.com>
---
 .../ABI/testing/sysfs-driver-hid-lamparray    |  15 +
 drivers/hid/Kconfig                           |  17 +
 drivers/hid/Makefile                          |   2 +
 drivers/hid/hid-lamparray.c                   | 853 ++++++++++++++++++
 include/linux/hid-lamparray.h                 |  88 ++
 5 files changed, 975 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-hid-lamparray
 create mode 100644 drivers/hid/hid-lamparray.c
 create mode 100644 include/linux/hid-lamparray.h

diff --git a/Documentation/ABI/testing/sysfs-driver-hid-lamparray b/Documentation/ABI/testing/sysfs-driver-hid-lamparray
new file mode 100644
index 000000000000..a118d168b3ba
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-hid-lamparray
@@ -0,0 +1,15 @@
+What:		/sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/use_leds_uapi
+Date:		December 2026
+KernelVersion:	7.4
+Contact:	aer@tuxedocomputers.com
+Description:
+        If a driver uses the hid-lamparray module and a device supporting
+        LampArray is found, one multicolor LED class device is registered under
+        /sys/class/leds/rgb:<function> to expose the single-zone RGB control.
+
+        Additionally, the use_leds_uapi sysfs attribute to control the LED class
+        device is attached directly to the HID device at
+        /sys/bus/hid/devices/<bus>:<vid>:<pid>.<n>/use_leds_uapi. Writing 0 to
+        use_leds_uapi unregisters the LED class device. The last state is kept
+        cached. Writing 1 registers it again and restores the cached state to
+        hardware.
diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index a81bf51cbcf1..ef1bb0037f4a 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -92,6 +92,23 @@ config HID_GENERIC
 
 	If unsure, say Y.
 
+config HID_LAMPARRAY
+	tristate "HID LampArray helper"
+	depends on HID
+	depends on LEDS_CLASS_MULTICOLOR
+	default n
+	help
+	  Helper for HID devices exposing a Lighting/LampArray collection.
+	  Treats LampArray devices as a single-zone device and exposes a sysfs
+	  interface for changing color and intensity values. Also exposes a
+	  sysfs flag to be disabled e.g. by a userspace driver.
+
+	  This can be used as library in existing drivers. The generic HID
+	  driver is extended by default to handle lamp array devices if this
+	  option is enabled.
+
+	  If unsure, say N.
+
 config HID_HAPTIC
 	bool "Haptic touchpad support"
 	default n
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index 48a863b245ee..f95630fa8bd8 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -13,6 +13,8 @@ obj-$(CONFIG_UHID)		+= uhid.o
 
 obj-$(CONFIG_HID_GENERIC)	+= hid-generic.o
 
+obj-$(CONFIG_HID_LAMPARRAY)	+= hid-lamparray.o
+
 hid-$(CONFIG_HIDRAW)		+= hidraw.o
 
 hid-logitech-y		:= hid-lg.o
diff --git a/drivers/hid/hid-lamparray.c b/drivers/hid/hid-lamparray.c
new file mode 100644
index 000000000000..acc00950495b
--- /dev/null
+++ b/drivers/hid/hid-lamparray.c
@@ -0,0 +1,853 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * hid-lamparray.c - HID LampArray helper module (single-zone RGB)
+ *
+ * Helper module for HID drivers supporting devices that expose a Lighting and
+ * Illumination (LampArray) application collection (usage page 0x59).
+ *
+ * The module provides a minimal integration with the LED subsystem and treats
+ * the device as a single zone: all lamps share one RGB value and a global
+ * brightness level. It does not implement multi-zone layouts or hardware
+ * effects.
+ *
+ * If enabled and a device supporting LampArray is found, one multicolor LED
+ * class device is registered under /sys/class/leds/rgb:<function> to expose the
+ * single-zone RGB control.
+ *
+ * The use_leds_uapi sysfs attribute is attached directly to the HID device
+ * under /sys/bus/hid/devices/<HID-ID>/use_leds_uapi. Writing 0 to use_leds_uapi
+ * unregisters the LED class device. The last state is kept cached. Writing 1
+ * registers it again and restores the cached state to hardware. State is cached
+ * as last known RGB + brightness.
+ *
+ * The module does not bind to devices on its own. Instead, a HID driver may
+ * query support via lamparray_is_supported_device() after hid_parse() and
+ * create an instance using lamparray_register().
+ *
+ * Copyright (C) 2026 Tim Guttzeit <tgu@tuxedocomputers.com>
+ * Copyright (C) 2026 Aaron Erhardt <aer@tuxedocomputers.com>
+ */
+
+#include <linux/device.h>
+#include <linux/limits.h>
+#include <linux/minmax.h>
+#include <linux/hid.h>
+#include <linux/leds.h>
+#include <linux/sysfs.h>
+#include <linux/hid-lamparray.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/container_of.h>
+#include <linux/led-class-multicolor.h>
+#include <linux/xarray.h>
+
+/* Constants */
+
+/* HID usages (LampArray, etc.) */
+#define HID_LIGHTING_ILLUMINATION_USAGE_PAGE	0x0059
+
+/* HID usage types */
+#define HID_APPLICATION_COLLECTION_USAGE_TYPE	0x0001
+#define HID_LAMPARRAY_ATTRIBUTES_REPORT		0x0002
+#define HID_LAMP_ATTRIBUTES_RESPONSE_REPORT	0x0022
+#define HID_LAMP_RANGE_UPDATE_REPORT		0x0060
+#define HID_LAMPARRAY_CONTROL_REPORT		0x0070
+
+/* HID attributes */
+#define HID_LAIP_LAMP_COUNT			0x0003
+#define HID_LAIP_LAMPARRAY_KIND			0x0007
+#define HID_LAIP_RED_LEVEL_COUNT		0x0028
+#define HID_LAIP_GREEN_LEVEL_COUNT		0x0029
+#define HID_LAIP_BLUE_LEVEL_COUNT		0x002a
+#define HID_LAIP_INTENSITY_LEVEL_COUNT		0x002b
+#define HID_LAIP_RED_UPDATE_CHANNEL		0x0051
+#define HID_LAIP_GREEN_UPDATE_CHANNEL		0x0052
+#define HID_LAIP_BLUE_UPDATE_CHANNEL		0x0053
+#define HID_LAIP_INTENSITY_UPDATE_CHANNEL	0x0054
+#define HID_LAIP_LAMP_ID_START			0x0061
+#define HID_LAIP_LAMP_ID_END			0x0062
+#define HID_LAIP_AUTONOMOUS_MODE		0x0071
+
+/* LampArrayKind values */
+#define HID_LAMPARRAY_KIND_KEYBOARD		0x0001
+
+/* Helper struct for fields and their indices */
+struct hid_field_value {
+	struct hid_field *field;
+	int index;
+};
+
+/* Helper struct for color fields */
+struct lamparray_color_fields {
+	struct hid_field_value red;
+	struct hid_field_value green;
+	struct hid_field_value blue;
+	struct hid_field_value intensity;
+};
+
+/* Device state */
+struct lamparray_device {
+	struct hid_device *hdev;
+
+	struct lamparray_color_fields color_levels;
+	struct lamparray_color_fields color_update;
+
+	struct hid_field_value autonomous_field;
+	struct hid_field_value range_start;
+	struct hid_field_value range_end;
+	struct hid_field_value lamp_count;
+	struct hid_field_value lamparray_kind;
+
+	u16 lamp_count_value;
+	u32 lamparray_kind_value;
+
+	struct led_classdev_mc mc_cdev;
+	struct mc_subled subleds[3];
+
+	struct mutex dev_lock; /* Protects cached state and HID access */
+
+	u8 max_r;
+	u8 max_g;
+	u8 max_b;
+	u8 max_brightness;
+
+	u8 last_r;
+	u8 last_g;
+	u8 last_b;
+	u8 last_brightness;
+
+	struct mutex sysfs_lock; /* Protects sysfs LED (de-)initialization */
+
+	bool use_leds_uapi;
+	bool led_registered;
+};
+
+/*
+ * Opaque handle exposed to callers via the header.
+ * Keep the actual state in lamparray_device, but return a stable pointer.
+ */
+struct lamparray {
+	struct lamparray_device ldev;
+};
+
+/*
+ * Mapping for hid_device pointers to their lamparray data.
+ * Since there is not guarantee of how the driver using this library
+ * will use its drvdata, the only safe way to retrieve the lamparray
+ * data from a HID device pointer is using this mapping.
+ */
+static DEFINE_XARRAY(lamparray_by_hdev);
+
+/* HID helper functions */
+
+static int get_field_value(struct hid_field_value *field_value)
+{
+	return field_value->field->value[field_value->index];
+}
+
+static u8 get_field_value_as_u8(struct hid_field_value *field_value)
+{
+	return clamp_val(get_field_value(field_value), 0, U8_MAX);
+}
+
+static void set_field_value(struct hid_field_value *field_value, int value)
+{
+	field_value->field->value[field_value->index] = value;
+}
+
+static bool lamparray_color_fields_is_complete(struct lamparray_color_fields *color_fields)
+{
+	return color_fields->red.field && color_fields->green.field &&
+	       color_fields->blue.field && color_fields->intensity.field;
+}
+
+static int lamparray_read_attributes_report(struct lamparray_device *ldev)
+{
+	struct hid_device *hdev = ldev->hdev;
+	struct hid_report *report;
+	int ret;
+	size_t len;
+
+	if (!ldev->lamp_count.field) {
+		hid_warn(hdev, "No LampCount field found\n");
+		return -ENODEV;
+	}
+
+	if (!ldev->lamparray_kind.field) {
+		hid_warn(hdev, "No LampArrayKind field found\n");
+		return -ENODEV;
+	}
+
+	report = ldev->lamp_count.field->report;
+
+	if (!report) {
+		hid_warn(hdev, "LampCount field has no report\n");
+		return -ENODEV;
+	}
+
+	len = hid_report_len(report);
+	u8 *buf __free(kfree) = kmalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	guard(mutex)(&ldev->dev_lock);
+
+	/* Update values */
+	ret = hid_hw_raw_request(hdev, report->id, buf, len,
+				 HID_FEATURE_REPORT, HID_REQ_GET_REPORT);
+	if (ret < 0) {
+		hid_warn(hdev, "Failed to request LampArrayAttributesReport: %d\n", ret);
+		return ret;
+	}
+
+	ret = hid_report_raw_event(hdev, HID_FEATURE_REPORT, buf, len, ret, 0);
+	if (ret < 0) {
+		hid_warn(hdev, "Failed to parse LampArrayAttributesReport: %d\n", ret);
+		return ret;
+	}
+
+	ldev->lamp_count_value = get_field_value(&ldev->lamp_count);
+	if (!ldev->lamp_count_value) {
+		hid_warn(hdev, "LampCount is 0 (invalid)\n");
+		return -EINVAL;
+	}
+
+	ldev->lamparray_kind_value = get_field_value(&ldev->lamparray_kind);
+	return 0;
+}
+
+static int lamparray_parse_update_report(struct lamparray_device *ldev)
+{
+	struct hid_device *hdev = ldev->hdev;
+	struct hid_report_enum *re;
+	struct hid_report *report;
+	struct hid_field *field;
+	int i, j;
+	int ret = 0;
+
+	re = &hdev->report_enum[HID_FEATURE_REPORT];
+
+	list_for_each_entry(report, &re->report_list, list) {
+		for (i = 0; i < report->maxfield; i++) {
+			field = report->field[i];
+			if (!field)
+				continue;
+
+			if (!field->usage || !field->maxusage)
+				continue;
+
+			for (j = 0; j < field->maxusage; j++) {
+				u32 usage = field->usage[j].hid;
+				u32 collection_idx = field->usage[j].collection_index;
+				u32 collection_usage = hdev->collection[collection_idx].usage;
+
+				u16 page = (usage & HID_USAGE_PAGE) >> 16;
+				u16 id = usage & HID_USAGE;
+				u16 collection_usage_id = collection_usage & U16_MAX;
+
+				if (page != HID_LIGHTING_ILLUMINATION_USAGE_PAGE)
+					continue;
+
+				if (collection_usage_id == HID_LAMPARRAY_ATTRIBUTES_REPORT) {
+					switch (id) {
+					case HID_LAIP_LAMP_COUNT:
+						ldev->lamp_count.field = field;
+						ldev->lamp_count.index = j;
+						break;
+					case HID_LAIP_LAMPARRAY_KIND:
+						ldev->lamparray_kind.field = field;
+						ldev->lamparray_kind.index = j;
+						break;
+					}
+				} else if (collection_usage_id ==
+					   HID_LAMP_ATTRIBUTES_RESPONSE_REPORT) {
+					switch (id) {
+					case HID_LAIP_RED_LEVEL_COUNT:
+						ldev->color_levels.red.field = field;
+						ldev->color_levels.red.index = j;
+						break;
+					case HID_LAIP_GREEN_LEVEL_COUNT:
+						ldev->color_levels.green.field = field;
+						ldev->color_levels.green.index = j;
+						break;
+					case HID_LAIP_BLUE_LEVEL_COUNT:
+						ldev->color_levels.blue.field = field;
+						ldev->color_levels.blue.index = j;
+						break;
+					case HID_LAIP_INTENSITY_LEVEL_COUNT:
+						ldev->color_levels.intensity.field = field;
+						ldev->color_levels.intensity.index = j;
+						break;
+					}
+				} else if (collection_usage_id == HID_LAMP_RANGE_UPDATE_REPORT) {
+					switch (id) {
+					case HID_LAIP_RED_UPDATE_CHANNEL:
+						ldev->color_update.red.field = field;
+						ldev->color_update.red.index = j;
+						break;
+					case HID_LAIP_GREEN_UPDATE_CHANNEL:
+						ldev->color_update.green.field = field;
+						ldev->color_update.green.index = j;
+						break;
+					case HID_LAIP_BLUE_UPDATE_CHANNEL:
+						ldev->color_update.blue.field = field;
+						ldev->color_update.blue.index = j;
+						break;
+					case HID_LAIP_INTENSITY_UPDATE_CHANNEL:
+						ldev->color_update.intensity.field = field;
+						ldev->color_update.intensity.index = j;
+						break;
+					case HID_LAIP_LAMP_ID_START:
+						ldev->range_start.field = field;
+						ldev->range_start.index = j;
+						break;
+					case HID_LAIP_LAMP_ID_END:
+						ldev->range_end.field = field;
+						ldev->range_end.index = j;
+						break;
+					default:
+						break;
+					}
+				} else if (collection_usage_id == HID_LAMPARRAY_CONTROL_REPORT &&
+					   id == HID_LAIP_AUTONOMOUS_MODE) {
+					ldev->autonomous_field.field = field;
+					ldev->autonomous_field.index = j;
+				}
+			}
+		}
+	}
+
+	if (!ldev->autonomous_field.field ||
+	    !lamparray_color_fields_is_complete(&ldev->color_update))
+		ret = -ENODEV;
+
+	return ret;
+}
+
+static int lamparray_hw_set_autonomous(struct lamparray_device *ldev,
+				       bool enable)
+{
+	struct hid_device *hdev = ldev->hdev;
+	struct hid_field *field = ldev->autonomous_field.field;
+
+	if (!field)
+		return -ENODEV;
+
+	guard(mutex)(&ldev->dev_lock);
+	set_field_value(&ldev->autonomous_field, !!enable);
+	hid_hw_request(hdev, field->report, HID_REQ_SET_REPORT);
+
+	return 0;
+}
+
+/* Make sure to hold dev lock to prevent concurrent access. */
+static int lamparray_hw_set_state(struct lamparray_device *ldev, u8 r, u8 g,
+				  u8 b, u8 intensity)
+{
+	struct hid_device *hdev = ldev->hdev;
+	struct hid_report *report;
+
+	if (!lamparray_color_fields_is_complete(&ldev->color_update))
+		return -ENODEV;
+
+	if (ldev->range_start.field && ldev->range_end.field) {
+		set_field_value(&ldev->range_start, 0);
+		set_field_value(&ldev->range_end, ldev->lamp_count_value - 1);
+	}
+
+	set_field_value(&ldev->color_update.red, r);
+	set_field_value(&ldev->color_update.green, g);
+	set_field_value(&ldev->color_update.blue, b);
+	set_field_value(&ldev->color_update.intensity, intensity);
+
+	report = ldev->color_update.red.field->report;
+	hid_hw_request(hdev, report, HID_REQ_SET_REPORT);
+
+	return 0;
+}
+
+/*
+ * Simple helper to read the color information of the first lamp.
+ * This does not read the state of the whole lamp array since this driver only
+ * exposes one LED anyway, so one color is sufficient here for now.
+ */
+static int lamparray_get_lamp_attributes(struct lamparray_device *ldev)
+{
+	struct hid_device *hdev = ldev->hdev;
+	struct hid_report *report;
+	int ret;
+	size_t len;
+
+	if (!lamparray_color_fields_is_complete(&ldev->color_levels))
+		return -ENODEV;
+
+	/*
+	 * All four fields must share the same report since the
+	 * attributes are fetched with a single GET_REPORT below.
+	 */
+	report = ldev->color_levels.red.field->report;
+	if (!report ||
+	    ldev->color_levels.green.field->report != report ||
+	    ldev->color_levels.blue.field->report != report ||
+	    ldev->color_levels.intensity.field->report != report)
+		return -ENODEV;
+
+	len = hid_report_len(report);
+	u8 *buf __free(kfree) = kmalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	guard(mutex)(&ldev->dev_lock);
+
+	/* Update values */
+	ret = hid_hw_raw_request(hdev, report->id, buf, len,
+				 HID_FEATURE_REPORT, HID_REQ_GET_REPORT);
+	if (ret < 0) {
+		hid_warn(hdev, "Failed to request LampAttributesResponseReport: %d\n", ret);
+		return ret;
+	}
+
+	ret = hid_report_raw_event(hdev, HID_FEATURE_REPORT, buf, len, ret, 0);
+	if (ret < 0) {
+		hid_warn(hdev, "Failed to parse LampAttributesResponseReport: %d\n", ret);
+		return ret;
+	}
+
+	ldev->max_r = get_field_value_as_u8(&ldev->color_levels.red);
+	ldev->max_g = get_field_value_as_u8(&ldev->color_levels.green);
+	ldev->max_b = get_field_value_as_u8(&ldev->color_levels.blue);
+	ldev->max_brightness = get_field_value_as_u8(&ldev->color_levels.intensity);
+
+	if (!ldev->max_r || !ldev->max_g || !ldev->max_b || !ldev->max_brightness) {
+		hid_warn(hdev, "LampArray device has no color levels\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* Helper functions */
+
+static int lamparray_restore_state(struct lamparray_device *ldev)
+{
+	u8 r, g, b;
+	int ret;
+	enum led_brightness brightness;
+
+	if (!ldev->use_leds_uapi)
+		return 0;
+
+	guard(mutex)(&ldev->dev_lock);
+
+	r = ldev->last_r;
+	g = ldev->last_g;
+	b = ldev->last_b;
+	brightness = ldev->last_brightness;
+
+	ldev->mc_cdev.subled_info[0].intensity = r;
+	ldev->mc_cdev.subled_info[1].intensity = g;
+	ldev->mc_cdev.subled_info[2].intensity = b;
+	ldev->mc_cdev.led_cdev.brightness = brightness;
+
+	/*
+	 * Quirk for devices ignoring intensity values, see
+	 * lamparray_led_brightness_set for more information.
+	 */
+	if (brightness)
+		ret = lamparray_hw_set_state(ldev, r, g, b, brightness);
+	else
+		ret = lamparray_hw_set_state(ldev, 0, 0, 0, 0);
+
+	return ret;
+}
+
+/* LEDs API */
+
+static int lamparray_led_brightness_set(struct led_classdev *cdev,
+					enum led_brightness brightness)
+{
+	struct led_classdev_mc *mc = lcdev_to_mccdev(cdev);
+	struct lamparray_device *ldev =
+		container_of_const(mc, struct lamparray_device, mc_cdev);
+	u8 r, g, b;
+	int ret;
+
+	/*
+	 * Brightness is handled by the LampArray device if supported,
+	 * so we can pass the raw intensity values.
+	 */
+	r = mc->subled_info[0].intensity;
+	g = mc->subled_info[1].intensity;
+	b = mc->subled_info[2].intensity;
+	mc->led_cdev.brightness = brightness;
+
+	guard(mutex)(&ldev->dev_lock);
+
+	/*
+	 * Some devices completely ignore the intensity (brightness)
+	 * value and instead rely on zeros for each RGB channel to turn
+	 * the LEDs off (e.g. the ASUS Prime B650-Plus). Since it doesn't
+	 * hurt spec-compliant devices to quirk this behavior, we turn
+	 * off the RGB channels unconditionally when the brightness is
+	 * zero.
+	 */
+	if (brightness)
+		ret = lamparray_hw_set_state(ldev, r, g, b, brightness);
+	else
+		ret = lamparray_hw_set_state(ldev, 0, 0, 0, 0);
+
+	if (ret) {
+		hid_err(ldev->hdev, "Failed to send LampArray update: %d\n",
+			ret);
+		return ret;
+	}
+
+	ldev->last_r = r;
+	ldev->last_g = g;
+	ldev->last_b = b;
+	ldev->last_brightness = brightness;
+
+	return 0;
+}
+
+static enum led_brightness
+lamparray_led_brightness_get(struct led_classdev *cdev)
+{
+	struct led_classdev_mc *mc = lcdev_to_mccdev(cdev);
+	struct lamparray_device *ldev =
+	    container_of_const(mc, struct lamparray_device, mc_cdev);
+
+	return ldev->last_brightness;
+}
+
+/* Make sure to hold sysfs lock to prevent concurrent access. */
+static int lamparray_register_led(struct lamparray_device *ldev)
+{
+	struct device *dev = &ldev->hdev->dev;
+	struct led_classdev *cdev = &ldev->mc_cdev.led_cdev;
+	int ret;
+
+	if (ldev->led_registered)
+		return 0;
+
+	if (!cdev->name) {
+		/* Fallback value */
+		const char *function = LED_FUNCTION_STATUS;
+
+		/* Some heuristics for choosing a better LED function. */
+		if (ldev->lamparray_kind_value == HID_LAMPARRAY_KIND_KEYBOARD)
+			function = LED_FUNCTION_KBD_BACKLIGHT;
+
+		cdev->name = kasprintf(GFP_KERNEL, "rgb:%s", function);
+		if (!cdev->name)
+			return -ENOMEM;
+	}
+
+	mutex_lock(&ldev->dev_lock);
+	/* Setup */
+	cdev->max_brightness = ldev->max_brightness;
+	cdev->brightness_set_blocking = lamparray_led_brightness_set;
+	cdev->brightness_get = lamparray_led_brightness_get;
+	/* Don't do anything automatically on shutdown or suspend. */
+	cdev->flags |= LED_RETAIN_AT_SHUTDOWN;
+
+	ldev->subleds[0].color_index = LED_COLOR_ID_RED;
+	ldev->subleds[0].max_intensity = ldev->max_r;
+	ldev->subleds[1].color_index = LED_COLOR_ID_GREEN;
+	ldev->subleds[1].max_intensity = ldev->max_g;
+	ldev->subleds[2].color_index = LED_COLOR_ID_BLUE;
+	ldev->subleds[2].max_intensity = ldev->max_b;
+
+	/* Set values */
+	ldev->subleds[0].intensity = ldev->last_r;
+	ldev->subleds[1].intensity = ldev->last_g;
+	ldev->subleds[2].intensity = ldev->last_b;
+	cdev->brightness = ldev->last_brightness;
+
+	ldev->mc_cdev.subled_info = ldev->subleds;
+	ldev->mc_cdev.num_colors = ARRAY_SIZE(ldev->subleds);
+
+	mutex_unlock(&ldev->dev_lock);
+
+	ret = led_classdev_multicolor_register(dev, &ldev->mc_cdev);
+	if (ret) {
+		hid_warn(ldev->hdev, "Failed to register LED classdev for lamparray\n");
+		kfree(cdev->name);
+		cdev->name = NULL;
+		return ret;
+	}
+
+	ldev->led_registered = true;
+
+	return 0;
+}
+
+/* Make sure to hold sysfs lock to prevent concurrent access. */
+static void lamparray_unregister_led(struct lamparray_device *ldev)
+{
+	struct led_classdev *cdev = &ldev->mc_cdev.led_cdev;
+
+	if (ldev->led_registered)
+		led_classdev_multicolor_unregister(&ldev->mc_cdev);
+
+	ldev->led_registered = false;
+	kfree(cdev->name);
+	cdev->name = NULL;
+}
+
+/* Sysfs */
+
+static struct lamparray_device *
+lamparray_ldev_from_sysfs_dev(struct device *dev)
+{
+	struct hid_device *hdev = to_hid_device(dev);
+
+	return xa_load(&lamparray_by_hdev, (unsigned long)hdev);
+}
+
+static ssize_t use_leds_uapi_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct lamparray_device *ldev = lamparray_ldev_from_sysfs_dev(dev);
+
+	if (!ldev)
+		return -ENODEV;
+
+	return sysfs_emit(buf, "%d\n", ldev->use_leds_uapi);
+}
+
+static ssize_t use_leds_uapi_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t count)
+{
+	struct lamparray_device *ldev = lamparray_ldev_from_sysfs_dev(dev);
+	bool val, old_val;
+	int ret;
+
+	if (!ldev)
+		return -ENODEV;
+
+	ret = kstrtobool(buf, &val);
+	if (ret)
+		return ret;
+
+	/* Make sure only one concurrent write is possible */
+	guard(mutex)(&ldev->sysfs_lock);
+	old_val = ldev->use_leds_uapi;
+
+	if (val == old_val)
+		return count;
+
+	ldev->use_leds_uapi = val;
+
+	/*
+	 * Take the device out of autonomous mode before exposing the LED
+	 * class device, and hand it back afterwards, so that control is
+	 * transferred in both directions rather than only at probe.
+	 */
+	if (val == 1) {
+		ret = lamparray_hw_set_autonomous(ldev, false);
+		if (ret)
+			goto err_revert;
+		ret = lamparray_register_led(ldev);
+		if (ret) {
+			lamparray_hw_set_autonomous(ldev, true);
+			goto err_revert;
+		}
+		ret = lamparray_restore_state(ldev);
+		if (ret) {
+			hid_warn(ldev->hdev, "Could not restore state: %d\n", ret);
+			lamparray_unregister_led(ldev);
+			lamparray_hw_set_autonomous(ldev, true);
+			goto err_revert;
+		}
+	} else {
+		lamparray_unregister_led(ldev);
+		ret = lamparray_hw_set_autonomous(ldev, true);
+		if (ret) {
+			hid_warn(ldev->hdev, "Could not enable autonomous mode: %d\n", ret);
+			return count;
+		}
+	}
+
+	return count;
+
+err_revert:
+	ldev->use_leds_uapi = old_val;
+	return ret;
+}
+static DEVICE_ATTR_RW(use_leds_uapi);
+
+static int lamparray_register_sysfs(struct lamparray_device *ldev)
+{
+	struct device *dev = &ldev->hdev->dev;
+	int ret;
+
+	ret = device_create_file(dev, &dev_attr_use_leds_uapi);
+	if (ret)
+		hid_err(ldev->hdev,
+			"Failed to create lamparray sysfs group: %d\n", ret);
+
+	return ret;
+}
+
+static void lamparray_remove_sysfs(struct lamparray_device *ldev)
+{
+	device_remove_file(&ldev->hdev->dev, &dev_attr_use_leds_uapi);
+}
+
+/* Public API */
+
+bool lamparray_is_supported_device(struct hid_device *hdev)
+{
+	unsigned int i;
+
+	hid_dbg(hdev, "lamparray: walking %u collections\n",
+		hdev->maxcollection);
+
+	for (i = 0; i < hdev->maxcollection; i++) {
+		struct hid_collection *col = &hdev->collection[i];
+		u16 page = (col->usage & HID_USAGE_PAGE) >> 16;
+		u16 code = col->usage & HID_USAGE;
+
+		hid_dbg(hdev,
+			"lamparray:  collection[%u]: type=%u level=%u usage=0x%08x page=0x%04x code=0x%04x\n",
+			i, col->type, col->level, col->usage, page, code);
+
+		if (col->type == HID_COLLECTION_APPLICATION &&
+		    page == HID_LIGHTING_ILLUMINATION_USAGE_PAGE &&
+		    code == HID_APPLICATION_COLLECTION_USAGE_TYPE) {
+			return true;
+		}
+	}
+	return false;
+}
+EXPORT_SYMBOL_GPL(lamparray_is_supported_device);
+
+struct lamparray *
+lamparray_register(struct hid_device *hdev,
+		   const struct lamparray_init_state *led_init_state)
+{
+	int ret;
+	struct lamparray_device *ldev;
+
+	if (!hdev)
+		return ERR_PTR(-ENODEV);
+
+	struct lamparray *la __free(kfree) = kzalloc_obj(*la, GFP_KERNEL);
+	if (!la)
+		return ERR_PTR(-ENOMEM);
+
+	ldev = &la->ldev;
+
+	mutex_init(&ldev->dev_lock);
+	mutex_init(&ldev->sysfs_lock);
+	ldev->hdev = hdev;
+	ldev->use_leds_uapi = true;
+	ldev->led_registered = false;
+
+	ret = lamparray_parse_update_report(ldev);
+	if (ret) {
+		hid_err(hdev, "No LampArray update report found: %d\n", ret);
+		goto err_free;
+	}
+
+	ret = lamparray_read_attributes_report(ldev);
+	if (ret) {
+		hid_err(hdev,
+			"Could not determine LampCount: %d\n",
+			ret);
+		goto err_free;
+	}
+
+	ret = lamparray_get_lamp_attributes(ldev);
+	if (ret) {
+		hid_err(hdev,
+			"Faulty device. Could not query lamp attributes.\n");
+		goto err_free;
+	}
+
+	/* Use black (all zeros) as default. */
+	if (led_init_state) {
+		ldev->last_r = min(led_init_state->r, ldev->max_r);
+		ldev->last_g = min(led_init_state->g, ldev->max_g);
+		ldev->last_b = min(led_init_state->b, ldev->max_b);
+		ldev->last_brightness = min(led_init_state->brightness,
+					    ldev->max_brightness);
+	}
+
+	/* No locking needed, no races are possible before sysfs setup. */
+	ret = lamparray_register_led(ldev);
+	if (ret) {
+		hid_warn(hdev, "Failed to register LED UAPI: %d\n", ret);
+		ldev->use_leds_uapi = false;
+	}
+
+	ret = xa_err(xa_store(&lamparray_by_hdev, (unsigned long)hdev, ldev,
+			      GFP_KERNEL));
+	if (ret)
+		goto err_unregister_led;
+
+	ret = lamparray_register_sysfs(ldev);
+	if (ret)
+		goto err_xa_erase;
+
+	ret = lamparray_hw_set_autonomous(ldev, false);
+	if (ret) {
+		hid_err(hdev, "Could not disable autonomous mode: %d", ret);
+		goto err_remove_sysfs;
+	}
+
+	hid_info(hdev, "LampArray device registered\n");
+
+	ret = lamparray_restore_state(ldev);
+	if (ret) {
+		hid_err(hdev, "Failed to set default state: %d", ret);
+		goto err_remove_sysfs;
+	}
+
+	return_ptr(la);
+
+err_remove_sysfs:
+	lamparray_remove_sysfs(ldev);
+err_xa_erase:
+	xa_erase(&lamparray_by_hdev, (unsigned long)hdev);
+err_unregister_led:
+	mutex_lock(&ldev->sysfs_lock);
+	lamparray_unregister_led(ldev);
+	mutex_unlock(&ldev->sysfs_lock);
+err_free:
+	mutex_destroy(&ldev->dev_lock);
+	mutex_destroy(&ldev->sysfs_lock);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(lamparray_register);
+
+void lamparray_unregister(struct lamparray *la)
+{
+	struct lamparray_device *ldev;
+
+	if (!la)
+		return;
+
+	ldev = &la->ldev;
+
+	lamparray_hw_set_autonomous(ldev, true);
+
+	lamparray_remove_sysfs(ldev);
+	xa_erase(&lamparray_by_hdev, (unsigned long)ldev->hdev);
+
+	mutex_lock(&ldev->sysfs_lock);
+	lamparray_unregister_led(ldev);
+	mutex_unlock(&ldev->sysfs_lock);
+
+	mutex_destroy(&ldev->dev_lock);
+	mutex_destroy(&ldev->sysfs_lock);
+	kfree(la);
+}
+EXPORT_SYMBOL_GPL(lamparray_unregister);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Tim Guttzeit <tgu@tuxedocomputers.com>");
+MODULE_AUTHOR("Aaron Erhardt <aer@tuxedocomputers.com>");
+MODULE_DESCRIPTION("HID LampArray helper module (single-zone RGB)");
diff --git a/include/linux/hid-lamparray.h b/include/linux/hid-lamparray.h
new file mode 100644
index 000000000000..a77869728d12
--- /dev/null
+++ b/include/linux/hid-lamparray.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _HID_LAMPARRAY_H
+#define _HID_LAMPARRAY_H
+
+#include <linux/hid.h>
+#include <linux/err.h>
+#include <linux/types.h>
+
+struct lamparray;
+
+/*
+ * Optional initial LED state for lamparray_register().
+ * Used to define the initial state of a LampArray's LEDs.
+ */
+struct lamparray_init_state {
+	u8 r;
+	u8 g;
+	u8 b;
+	u8 brightness;
+};
+
+#if IS_ENABLED(CONFIG_HID_LAMPARRAY)
+
+/**
+ * lamparray_is_supported_device() - check whether a HID device supports LampArray
+ * @hdev: HID device to inspect
+ *
+ * Check whether the given HID device exposes a Lighting/LampArray application
+ * collection as defined by the HID Lighting specification.
+ *
+ * This helper can be used by HID drivers to determine whether LampArray
+ * functionality should be enabled for a device.
+ *
+ * Return: %true if LampArray support is detected, %false otherwise.
+ */
+bool lamparray_is_supported_device(struct hid_device *hdev);
+
+/**
+ * lamparray_register() - initialize LampArray support for a HID device
+ * @hdev: HID device
+ * @led_init_state: Optional LED state at init specification
+ *
+ * Allocate and initialize internal LampArray state for the given HID device.
+ * The function parses required HID reports and fields and registers the
+ * associated miscdevice and sysfs attributes.
+ *
+ * Registers a multicolor LED class device to expose the LampArray functionality
+ * via the LED subsystem. If specified, the desired initial LED state is
+ * applied. If led_init_state is NULL, a default state is applied (all LEDs off).
+ *
+ * Return: pointer to a LampArray handle on success, or ERR_PTR() on failure.
+ */
+struct lamparray *lamparray_register(struct hid_device *hdev,
+				     const struct lamparray_init_state *led_init_state);
+
+/**
+ * lamparray_unregister() - tear down LampArray support
+ * @la: LampArray handle returned by lamparray_register()
+ *
+ * Remove all resources associated with a LampArray instance.
+ *
+ * This unregisters the LED class device (if present), removes the miscdevice
+ * and sysfs interfaces and frees all internal state associated with @la.
+ */
+void lamparray_unregister(struct lamparray *la);
+
+#else /* !CONFIG_HID_LAMPARRAY */
+
+static inline bool lamparray_is_supported_device(struct hid_device *hdev)
+{
+	return false;
+}
+
+static inline struct lamparray *
+lamparray_register(struct hid_device *hdev,
+		   const struct lamparray_init_state *led_init_state)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
+static inline void lamparray_unregister(struct lamparray *la)
+{
+}
+
+#endif /* CONFIG_HID_LAMPARRAY */
+
+#endif /* _HID_LAMPARRAY_H */
-- 
2.43.0

[PATCH v6 2/3] HID: generic: add LampArray support via hid-lamparray helper

[Aaron Erhardt]

The hid-generic driver now checks for LampArray support after
hid_parse() and optionally registers a lamparray instance. Failures in
the helper do not abort device probe to keep the device unchanged.

LampArray resources are released on driver remove.

This patch was successfully tested on the Microsoft MacroPad reference
implementation (https://github.com/microsoft/RP2040MacropadHidSample
1d6c3ad) and in combination with the tuxedo_nb04_wmi driver, albeit only
functional with a recent fix posted to the LKML.

Link:
https://lore.kernel.org/all/20260728115918.125349-2-aer@tuxedocomputers.com

Co-developed-by: Tim Guttzeit <tgu@tuxedocomputers.com>
Signed-off-by: Tim Guttzeit <tgu@tuxedocomputers.com>
Signed-off-by: Aaron Erhardt <aer@tuxedocomputers.com>
---
 drivers/hid/Kconfig       |  1 +
 drivers/hid/hid-generic.c | 41 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index ef1bb0037f4a..7f9529fd6011 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -82,6 +82,7 @@ config UHID
 
 config HID_GENERIC
 	tristate "Generic HID driver"
+	depends on HID_LAMPARRAY if HID_LAMPARRAY
 	default HID
 	help
 	Support for generic devices on the HID bus. This includes most
diff --git a/drivers/hid/hid-generic.c b/drivers/hid/hid-generic.c
index c2de916747de..fde772c5014b 100644
--- a/drivers/hid/hid-generic.c
+++ b/drivers/hid/hid-generic.c
@@ -20,6 +20,7 @@
 #include <asm/byteorder.h>
 
 #include <linux/hid.h>
+#include <linux/hid-lamparray.h>
 
 static struct hid_driver hid_generic;
 
@@ -60,6 +61,7 @@ static int hid_generic_probe(struct hid_device *hdev,
 			     const struct hid_device_id *id)
 {
 	int ret;
+	struct lamparray *la;
 
 	hdev->quirks |= HID_QUIRK_INPUT_PER_APP;
 
@@ -67,6 +69,34 @@ static int hid_generic_probe(struct hid_device *hdev,
 	if (ret)
 		return ret;
 
+	/*
+	 * Optional: attach LampArray support if present.
+	 * Never fail probe on LampArray errors; keep device functional.
+	 */
+	if (IS_ENABLED(CONFIG_HID_LAMPARRAY) && lamparray_is_supported_device(hdev)) {
+		/*
+		 * Use HID_CONNECT_DRIVER to make sure requests are
+		 * processed in hid_report_raw_event. Without this,
+		 * hid-core will skip parsing for devices that are only
+		 * claimed by hidraw, thus making it impossible to query
+		 * the required information.
+		 * See 7704ac937345 for more information about this flag
+		 * and why it is necessary.
+		 */
+		ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT | HID_CONNECT_DRIVER);
+		if (ret)
+			return ret;
+
+		la = lamparray_register(hdev, NULL);
+		if (IS_ERR(la)) {
+			hid_hw_stop(hdev);
+			hid_warn(hdev, "LampArray init failed: %ld\n", PTR_ERR(la));
+		} else {
+			hid_set_drvdata(hdev, la);
+			return 0;
+		}
+	}
+
 	return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
 }
 
@@ -78,6 +108,16 @@ static int hid_generic_reset_resume(struct hid_device *hdev)
 	return 0;
 }
 
+static void hid_generic_remove(struct hid_device *hdev)
+{
+	struct lamparray *la = hid_get_drvdata(hdev);
+
+	if (IS_ENABLED(CONFIG_HID_LAMPARRAY) && la)
+		lamparray_unregister(la);
+
+	hid_hw_stop(hdev);
+}
+
 static const struct hid_device_id hid_table[] = {
 	{ HID_DEVICE(HID_BUS_ANY, HID_GROUP_ANY, HID_ANY_ID, HID_ANY_ID) },
 	{ }
@@ -90,6 +130,7 @@ static struct hid_driver hid_generic = {
 	.match = hid_generic_match,
 	.probe = hid_generic_probe,
 	.reset_resume = hid_generic_reset_resume,
+	.remove = hid_generic_remove,
 };
 module_hid_driver(hid_generic);
 
-- 
2.43.0

[PATCH v6 3/3] HID: lamparray: blank lamps across suspend and restore on resume

[Aaron Erhardt]

From: Cristian Mazzotta <cmmazzo@icloud.com>

The helper installs no PM callbacks, so lamps keep their last state
across suspend. Firmware is not required to turn them off in low power
states, and on devices where it does not, they stay lit for the whole
suspend.

On an Acer Predator PT14-52T, system power draw during s2idle is 12.35W
with the lamps lit and 2.84W with them blanked, measured at the charger.

Add lamparray_suspend(), which writes zeroes to the color channels
while leaving the cached RGB and brightness untouched, and
lamparray_resume(), which restores that cache. Both return early when
use_leds_uapi is 0 so a userspace driver keeps full control. hid-generic
gains suspend and resume callbacks to drive them, and calls
lamparray_resume() from reset_resume as well.

Some devices return to firmware control across a hibernate transition
while still reporting AutonomousMode = 0, and ignore host lamp updates
until the value genuinely transitions. Force a 1 -> 0 on resume
before restoring state.

Co-developed-by: Aaron Erhardt <aer@tuxedocomputers.com>
Signed-off-by: Aaron Erhardt <aer@tuxedocomputers.com>
Signed-off-by: Cristian Mazzotta <cmmazzo@icloud.com>
---
 drivers/hid/hid-generic.c     | 29 ++++++++++++++++++-
 drivers/hid/hid-lamparray.c   | 54 +++++++++++++++++++++++++++++++++++
 include/linux/hid-lamparray.h | 29 +++++++++++++++++++
 3 files changed, 111 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-generic.c b/drivers/hid/hid-generic.c
index fde772c5014b..f78c62f796fb 100644
--- a/drivers/hid/hid-generic.c
+++ b/drivers/hid/hid-generic.c
@@ -102,9 +102,34 @@ static int hid_generic_probe(struct hid_device *hdev,
 
 static int hid_generic_reset_resume(struct hid_device *hdev)
 {
+	struct lamparray *la = hid_get_drvdata(hdev);
+
 	if (hdev->claimed & HID_CLAIMED_INPUT)
 		hidinput_reset_resume(hdev);
 
+	if (IS_ENABLED(CONFIG_HID_LAMPARRAY) && la)
+		lamparray_resume(la);
+
+	return 0;
+}
+
+static int hid_generic_suspend(struct hid_device *hdev, pm_message_t message)
+{
+	struct lamparray *la = hid_get_drvdata(hdev);
+
+	if (IS_ENABLED(CONFIG_HID_LAMPARRAY) && la)
+		lamparray_suspend(la);
+
+	return 0;
+}
+
+static int hid_generic_resume(struct hid_device *hdev)
+{
+	struct lamparray *la = hid_get_drvdata(hdev);
+
+	if (IS_ENABLED(CONFIG_HID_LAMPARRAY) && la)
+		lamparray_resume(la);
+
 	return 0;
 }
 
@@ -129,8 +154,10 @@ static struct hid_driver hid_generic = {
 	.id_table = hid_table,
 	.match = hid_generic_match,
 	.probe = hid_generic_probe,
-	.reset_resume = hid_generic_reset_resume,
 	.remove = hid_generic_remove,
+	.reset_resume = pm_ptr(hid_generic_reset_resume),
+	.suspend = pm_ptr(hid_generic_suspend),
+	.resume = pm_ptr(hid_generic_resume),
 };
 module_hid_driver(hid_generic);
 
diff --git a/drivers/hid/hid-lamparray.c b/drivers/hid/hid-lamparray.c
index acc00950495b..c7d4d3d1b02d 100644
--- a/drivers/hid/hid-lamparray.c
+++ b/drivers/hid/hid-lamparray.c
@@ -847,6 +847,60 @@ void lamparray_unregister(struct lamparray *la)
 }
 EXPORT_SYMBOL_GPL(lamparray_unregister);
 
+/*
+ * Blank all lamps on suspend rather than handing control back to the firmware,
+ * which may not turn them off in low power states. On an Acer Predator PT14-52T,
+ * system power draw during s2idle was ~12.35W with lamps lit, and ~2.84W with
+ * them blanked; the lighting accounted for ~77% of the power draw during suspend.
+ * Since writing zeroes is well defined on all lamparray devices, always do it.
+ * This is ignored if use_leds_uapi is 0; let userspace keep full control.
+ */
+void lamparray_suspend(struct lamparray *la)
+{
+	struct lamparray_device *ldev;
+
+	if (!la)
+		return;
+
+	ldev = &la->ldev;
+
+	if (!ldev->use_leds_uapi)
+		return;
+
+	mutex_lock(&ldev->dev_lock);
+	lamparray_hw_set_state(ldev, 0, 0, 0, 0);
+	mutex_unlock(&ldev->dev_lock);
+
+	hid_hw_wait(ldev->hdev);
+}
+EXPORT_SYMBOL_GPL(lamparray_suspend);
+
+void lamparray_resume(struct lamparray *la)
+{
+	struct lamparray_device *ldev;
+
+	if (!la)
+		return;
+
+	ldev = &la->ldev;
+
+	if (!ldev->use_leds_uapi)
+		return;
+
+	/*
+	 * After a S4 transition, some devices report
+	 * AutonomousMode = 0 while still ignoring host lamp updates.
+	 * Writing 0 again does nothing; forcing a 1 -> 0
+	 * will guarantee the device will update.
+	 */
+	lamparray_hw_set_autonomous(ldev, true);
+	hid_hw_wait(ldev->hdev);
+	lamparray_hw_set_autonomous(ldev, false);
+
+	lamparray_restore_state(ldev);
+}
+EXPORT_SYMBOL_GPL(lamparray_resume);
+
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Tim Guttzeit <tgu@tuxedocomputers.com>");
 MODULE_AUTHOR("Aaron Erhardt <aer@tuxedocomputers.com>");
diff --git a/include/linux/hid-lamparray.h b/include/linux/hid-lamparray.h
index a77869728d12..f7d0e22305e5 100644
--- a/include/linux/hid-lamparray.h
+++ b/include/linux/hid-lamparray.h
@@ -65,6 +65,27 @@ struct lamparray *lamparray_register(struct hid_device *hdev,
  */
 void lamparray_unregister(struct lamparray *la);
 
+/**
+ * lamparray_suspend() - blank all lamps ahead of sleep transition
+ * @la: LampArray handle returned by lamparray_register()
+ *
+ * Writes zeroes to the rgb values only, keeping the brightness, unless the
+ * use_leds_uapi sysfs attribute is 0, in which case, it will return early
+ * before writing anything. The cached state is left untouched so
+ * lamparray_resume() can restore it.
+ */
+void lamparray_suspend(struct lamparray *la);
+
+/**
+ * lamparray_resume() - restore host control and LampArray state
+ * @la: LampArray handle returned by lamparray_register()
+ *
+ * Disables autonomous mode (in case device returns to firmware control after suspend)
+ * and restores the cached state of the device. If the use_leds_uapi attribute is 0,
+ * it will return early and prevent any unwanted writing.
+ */
+void lamparray_resume(struct lamparray *la);
+
 #else /* !CONFIG_HID_LAMPARRAY */
 
 static inline bool lamparray_is_supported_device(struct hid_device *hdev)
@@ -83,6 +104,14 @@ static inline void lamparray_unregister(struct lamparray *la)
 {
 }
 
+static inline void lamparray_suspend(struct lamparray *la)
+{
+}
+
+static inline void lamparray_resume(struct lamparray *la)
+{
+}
+
 #endif /* CONFIG_HID_LAMPARRAY */
 
 #endif /* _HID_LAMPARRAY_H */
-- 
2.43.0

Re: [PATCH v6 0/3] HID: generic: add LampArray support via hid-lamparray helper

[Cristian Mazzotta]

On 16.09.26 16:48, Aaron Erhardt wrote:
> Add a new hid-lamparray helper module and integrate it with the hid-generic
> driver.

Thanks for picking these up!

I do have two corrections on patch 3 however, and both were mine
originally, so my bad:

 - The measurement in the commit message and in the comment above
   lamparray_suspend() is wrong. It should be 12.35 W with lamps lit and
   3.14 W blanked, which is 9.21 W or about 75% of s2idle draw, not
   2.84 W / 77%. The 2.84 W was an earlier test on a local branch that
   includes full multi-zone support. It's worth noting in the comment that
   the 3.14 W still includes the lid zone, which single-zone control
   cannot reach on this device.

 - The kerneldoc for lamparray_suspend() still says it "writes zeroes to
   the rgb values only, keeping the brightness", but the call is now
   lamparray_hw_set_state(ldev, 0, 0, 0, 0). The code is fine, but the doc
   should follow it.

On your question about the default state: I think the lights "look like
they don't work" can be a real conclusion, but the cause is the intensity
default rather than the brightness default.

With led_init_state NULL, last_r/g/b stay zero, register_led copies
them into subleds[].intensity, and brightness_set reads r/g/b back out
of subled_info[].intensity. So every brightness write sends
(0, 0, 0, brightness), which is black at any brightness. The
zero-brightness quirk does not change this since it only forces RGB to
zero when brightness is already zero.

The LED class device is therefore inert rather than just dark;
systemd-backlight restoring a saved brightness, or a DE slider, or
UPower, all write brightness and see nothing happen. This is because
nothing in that stack writes multi_intensity first.

Defaulting to autonomous mode would not fix that. It would replace an
inert knob with an ignored one: the cached RGB and brightness would
describe nothing the hardware is doing, and a DE would have to
discover and write use_leds_uapi to make the node real. That is
driver-specific knowledge that desktop environments are unlikely to
carry.

On a second look, I would suggest keeping brightness at LED_OFF, but
defaulting the intensities to max_r/max_g/max_b. The device is still
dark at probe, autonomous mode is still disabled so the cached state
matches the hardware, and the first brightness write from existing
userspace lights it up. Combined with the quirk you added for Armin's
device, it stays dark even on firmware that ignores the intensity channel.

One hardware data point, since discoverability came up: on the Acer
Predator PT14-52T the keyboard brightness keys are handled entirely in
the EC and never reach the LED class device, so they cannot be relied
on to show the user that anything is controllable.

On multi-collection, I don't see myself getting to it soon. I might work
on it during fall or winter break of my university, however I cannot
guarantee it, so please do not consider it blocked on me. The ENE
controller exposes two LampArrayAttributesReport collections and
lamparray_parse_update_report() only keeps the last.

I have a local branch which includes working multi-collection support.
It's based off of Tim's v4, and it's what I referred to in the original
v4 thread; I'd be happy to send over my branch as a reference, though
porting it to v6 is not trivial.

Re: [PATCH v6 0/3] HID: generic: add LampArray support via hid-lamparray helper

[Aaron Erhardt]

Am 16.09.26 um 18:15 schrieb Cristian Mazzotta:
> On 16.09.26 16:48, Aaron Erhardt wrote:
>> Add a new hid-lamparray helper module and integrate it with the hid-generic
>> driver.
> 
> Thanks for picking these up!
> 
> I do have two corrections on patch 3 however, and both were mine
> originally, so my bad:
> 
>  - The measurement in the commit message and in the comment above
>    lamparray_suspend() is wrong. It should be 12.35 W with lamps lit and
>    3.14 W blanked, which is 9.21 W or about 75% of s2idle draw, not
>    2.84 W / 77%. The 2.84 W was an earlier test on a local branch that
>    includes full multi-zone support. It's worth noting in the comment that
>    the 3.14 W still includes the lid zone, which single-zone control
>    cannot reach on this device.
> 
>  - The kerneldoc for lamparray_suspend() still says it "writes zeroes to
>    the rgb values only, keeping the brightness", but the call is now
>    lamparray_hw_set_state(ldev, 0, 0, 0, 0). The code is fine, but the doc
>    should follow it.

Ack. Will be fixed in v7.

> 
> On your question about the default state: I think the lights "look like
> they don't work" can be a real conclusion, but the cause is the intensity
> default rather than the brightness default.
> 
> With led_init_state NULL, last_r/g/b stay zero, register_led copies
> them into subleds[].intensity, and brightness_set reads r/g/b back out
> of subled_info[].intensity. So every brightness write sends
> (0, 0, 0, brightness), which is black at any brightness. The
> zero-brightness quirk does not change this since it only forces RGB to
> zero when brightness is already zero.
> 
> The LED class device is therefore inert rather than just dark;
> systemd-backlight restoring a saved brightness, or a DE slider, or
> UPower, all write brightness and see nothing happen. This is because
> nothing in that stack writes multi_intensity first.
> 
> Defaulting to autonomous mode would not fix that. It would replace an
> inert knob with an ignored one: the cached RGB and brightness would
> describe nothing the hardware is doing, and a DE would have to
> discover and write use_leds_uapi to make the node real. That is
> driver-specific knowledge that desktop environments are unlikely to
> carry.
> 
> On a second look, I would suggest keeping brightness at LED_OFF, but
> defaulting the intensities to max_r/max_g/max_b. The device is still
> dark at probe, autonomous mode is still disabled so the cached state
> matches the hardware, and the first brightness write from existing
> userspace lights it up. Combined with the quirk you added for Armin's
> device, it stays dark even on firmware that ignores the intensity channel.

I think this is a good idea. In general, the default should probably
either set intensities to max_(r|g|b) or brightness to max_brightness.
This would reduce the amount of writes necessary to see a result and I
agree that probably the brightness knob is most likely to be used by
userspace. Still, I'd like to have some more feedback, especially from
the maintainers before integrating this behavior in v7.

> 
> One hardware data point, since discoverability came up: on the Acer
> Predator PT14-52T the keyboard brightness keys are handled entirely in
> the EC and never reach the LED class device, so they cannot be relied
> on to show the user that anything is controllable.
> 
> On multi-collection, I don't see myself getting to it soon. I might work
> on it during fall or winter break of my university, however I cannot
> guarantee it, so please do not consider it blocked on me. The ENE
> controller exposes two LampArrayAttributesReport collections and
> lamparray_parse_update_report() only keeps the last.
> 
> I have a local branch which includes working multi-collection support.
> It's based off of Tim's v4, and it's what I referred to in the original
> v4 thread; I'd be happy to send over my branch as a reference, though
> porting it to v6 is not trivial.

I could have a look at your branch, but I think it's better to wait for
this series to be merged before exploring more advanced features. I
can't guarantee that I will work on that actively, especially since I
don't have access to such hardware, but I'm curious to see what changes
you have applied to make it work with v4.