[PATCH v2] platform/x86: acer-wmi: support PH317-51 hwmon and kbd backlight

[Lucas Gillard <mirsella1@gmail.com>]

The Predator Helios 300 PH317-51 exposes early gaming WMI methods for
temperature and fan sensors, but lacks the platform-profile and
overclocking methods (22 and 23). Enable hwmon for this model without
enabling platform-profile support.

Its keyboard backlight is controlled by EC registers 0x30 and 0x31;
the WMI LED methods do not report or change it. Fn+F9 updates both EC
registers. Register an on/off keyboard LED with a blocking setter and
read its brightness directly from the EC, so sysfs reflects changes
made with Fn+F9.

Write both registers to match the firmware's on/off states. Use the LED
core to suspend and resume the backlight, reading its current state from
the EC before suspend.

Signed-off-by: Lucas Gillard <mirsella1@gmail.com>
Assisted-by: LLM
---
Hi Ilpo,

Thanks for the review. This revision is based on the platform-drivers-x86
for-next tree at 9d3475065167197742b0882aff21cf8e78393277.

Changes in v2:
- Use the existing hwmon quirk after the predator_v4 split.
- Name both EC registers and the state mask, and use them throughout.
- Convert brightness to an explicit u8 on/off value without modifying
  the enum argument; remove the redundant mask parentheses.
- Use brightness_set_blocking and return EC write errors.
- Use managed LED registration and remove the explicit off-write on
  unregister. LED core handles teardown.
- Use LED-core helpers for suspend, resume and shutdown, draining pending
  LED work before suspend/shutdown. Read the live EC state before suspend
  to preserve Fn+F9 changes.

I'm currently away from the machine and haven't retested v2 on hardware. I'm sending this update for review.

I used an LLM for code changes, review and local validation.

v1: https://lore.kernel.org/r/6aad63a9.f9180b46.32931.492b@mx.google.com
Review: https://lore.kernel.org/r/ea6d7395-c70f-9346-fc3f-9465adb5fef1@linux.intel.com

Thanks,
Lucas

 drivers/platform/x86/acer-wmi.c | 85 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 84 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/acer-wmi.c b/drivers/platform/x86/acer-wmi.c
index 3a018fdf513891a8a012aeaa7185a3de521ecf47..b893e04712966fb1d792e4eb27955f3dbc8fad1d 100644
--- a/drivers/platform/x86/acer-wmi.c
+++ b/drivers/platform/x86/acer-wmi.c
@@ -310,6 +310,11 @@ struct hotkey_function_type_aa {
 #define ACER_CAP_PLATFORM_PROFILE	BIT(10)
 #define ACER_CAP_HWMON			BIT(11)
 #define ACER_CAP_PWM			BIT(12)
+#define ACER_CAP_KBD_BACKLIGHT		BIT(13)
+
+#define ACER_KBD_BACKLIGHT_EC_STATE	0x30
+#define ACER_KBD_BACKLIGHT_EC_MIRROR	0x31
+#define ACER_KBD_BACKLIGHT_MASK		BIT(0)
 
 /*
  * Interface type flags
@@ -406,6 +411,7 @@ struct quirk_entry {
 	bool hwmon;
 	bool platform_profile;
 	bool pwm;
+	bool kbd_backlight;
 };
 
 static struct quirk_entry *quirks;
@@ -430,6 +436,9 @@ static void __init set_quirks(void)
 
 	if (quirks->pwm)
 		interface->capability |= ACER_CAP_PWM;
+
+	if (quirks->kbd_backlight)
+		interface->capability |= ACER_CAP_KBD_BACKLIGHT;
 }
 
 static int __init dmi_matched(const struct dmi_system_id *dmi)
@@ -474,6 +483,12 @@ static struct quirk_entry quirk_acer_predator_ph315_53 = {
 	.gpu_fans = 1,
 };
 
+/* Firmware supports sensors but lacks the platform-profile/OC methods. */
+static struct quirk_entry quirk_acer_predator_ph317_51 = {
+	.hwmon = true,
+	.kbd_backlight = true,
+};
+
 static struct quirk_entry quirk_acer_nitro_anv15_51 = {
 	.cpu_fans = 1,
 	.gpu_fans = 1,
@@ -717,6 +732,15 @@ static const struct dmi_system_id acer_quirks[] __initconst = {
 		},
 		.driver_data = &quirk_acer_predator_ph315_53,
 	},
+	{
+		.callback = dmi_matched,
+		.ident = "Acer Predator PH317-51",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Predator PH317-51"),
+		},
+		.driver_data = &quirk_acer_predator_ph317_51,
+	},
 	{
 		.callback = dmi_matched,
 		.ident = "Acer Predator PHN16-71",
@@ -1968,7 +1992,7 @@ static void __init acer_commandline_init(void)
 }
 
 /*
- * LED device (Mail LED only, no other LEDs known yet)
+ * Mail LED device
  */
 static void mail_led_set(struct led_classdev *led_cdev,
 enum led_brightness value)
@@ -1992,6 +2016,40 @@ static void acer_led_exit(void)
 	led_classdev_unregister(&mail_led);
 }
 
+/*
+ * No WMI method drives this keyboard backlight. Fn+F9 changes both EC
+ * registers, so write both to reproduce the firmware's on/off states.
+ */
+static int kbd_led_set(struct led_classdev *led_cdev,
+		       enum led_brightness brightness)
+{
+	u8 value = brightness == LED_OFF ? 0 : ACER_KBD_BACKLIGHT_MASK;
+	int ret;
+
+	ret = ec_write(ACER_KBD_BACKLIGHT_EC_STATE, value);
+	if (ret)
+		return ret;
+
+	return ec_write(ACER_KBD_BACKLIGHT_EC_MIRROR, value);
+}
+
+static enum led_brightness kbd_led_get(struct led_classdev *led_cdev)
+{
+	u8 value;
+
+	if (ec_read(ACER_KBD_BACKLIGHT_EC_STATE, &value))
+		return LED_OFF;
+
+	return value & ACER_KBD_BACKLIGHT_MASK ? LED_ON : LED_OFF;
+}
+
+static struct led_classdev kbd_led = {
+	.name = "acer-wmi::kbd_backlight",
+	.brightness_set_blocking = kbd_led_set,
+	.brightness_get = kbd_led_get,
+	.max_brightness = LED_ON,
+};
+
 /*
  * Backlight device
  */
@@ -2847,8 +2905,15 @@ static int acer_platform_probe(struct platform_device *device)
 			goto error_hwmon;
 	}
 
+	if (has_cap(ACER_CAP_KBD_BACKLIGHT)) {
+		err = devm_led_classdev_register(&device->dev, &kbd_led);
+		if (err)
+			goto error_kbd_backlight;
+	}
+
 	return 0;
 
+error_kbd_backlight:
 error_hwmon:
 error_platform_profile:
 	acer_rfkill_exit();
@@ -2877,6 +2942,7 @@ static int acer_suspend(struct device *dev)
 {
 	u32 value;
 	struct acer_data *data = &interface->data;
+	int ret;
 
 	if (!data)
 		return -ENOMEM;
@@ -2892,6 +2958,17 @@ static int acer_suspend(struct device *dev)
 		data->brightness = value;
 	}
 
+	if (has_cap(ACER_CAP_KBD_BACKLIGHT)) {
+		u8 state;
+
+		ret = ec_read(ACER_KBD_BACKLIGHT_EC_STATE, &state);
+		if (ret)
+			return ret;
+
+		kbd_led.brightness = state & ACER_KBD_BACKLIGHT_MASK;
+		led_classdev_suspend(&kbd_led);
+	}
+
 	return 0;
 }
 
@@ -2908,6 +2985,9 @@ static int acer_resume(struct device *dev)
 	if (has_cap(ACER_CAP_BRIGHTNESS))
 		set_u32(data->brightness, ACER_CAP_BRIGHTNESS);
 
+	if (has_cap(ACER_CAP_KBD_BACKLIGHT))
+		led_classdev_resume(&kbd_led);
+
 	if (acer_wmi_accel_dev)
 		acer_gsensor_init();
 
@@ -2929,6 +3009,9 @@ static void acer_platform_shutdown(struct platform_device *device)
 
 	if (has_cap(ACER_CAP_MAILLED))
 		set_u32(LED_OFF, ACER_CAP_MAILLED);
+
+	if (has_cap(ACER_CAP_KBD_BACKLIGHT))
+		led_classdev_suspend(&kbd_led);
 }
 
 static struct platform_driver acer_platform_driver = {

base-commit: 9d3475065167197742b0882aff21cf8e78393277