Re: [PATCH v6 4/7] HID: asus: listen to the asus-wmi brightness device instead of creating one

[Denis Benato <benato.denis96@gmail.com>]

On 10/13/25 22:15, Antheas Kapenekakis wrote:
> Some ROG laptops expose multiple interfaces for controlling the
> keyboard/RGB brightness. This creates a name conflict under
> asus::kbd_brightness, where the second device ends up being
> named asus::kbd_brightness_1 and they are both broken.
Can you please reference a bug report and/or an analysis of why they ends
up being broken?
>
> Therefore, register a listener to the asus-wmi brightness device
> instead of creating a new one.
>
> Reviewed-by: Luke D. Jones <luke@ljones.dev>
> Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
> ---
>  drivers/hid/hid-asus.c | 64 +++++++-----------------------------------
>  1 file changed, 10 insertions(+), 54 deletions(-)
>
> diff --git a/drivers/hid/hid-asus.c b/drivers/hid/hid-asus.c
> index a62559e3e064..0af19c8ef035 100644
> --- a/drivers/hid/hid-asus.c
> +++ b/drivers/hid/hid-asus.c
> @@ -102,7 +102,7 @@ MODULE_DESCRIPTION("Asus HID Keyboard and TouchPad");
>  #define TRKID_SGN       ((TRKID_MAX + 1) >> 1)
>  
>  struct asus_kbd_leds {
> -	struct led_classdev cdev;
> +	struct asus_hid_listener listener;
It is my understanding from "register a listener .... instead of creating a new one"
that you are attempting to use the same listener among many devices... so why isn't
this a pointer? And more importantly: why do we have bool available, bool registered
instead of either one or the other being replaced by this field being possibly NULL?
>  	struct hid_device *hdev;
>  	struct work_struct work;
>  	unsigned int brightness;
> @@ -495,11 +495,11 @@ static void asus_schedule_work(struct asus_kbd_leds *led)
>  	spin_unlock_irqrestore(&led->lock, flags);
>  }
>  
> -static void asus_kbd_backlight_set(struct led_classdev *led_cdev,
> -				   enum led_brightness brightness)
> +static void asus_kbd_backlight_set(struct asus_hid_listener *listener,
> +				   int brightness)
>  {
> -	struct asus_kbd_leds *led = container_of(led_cdev, struct asus_kbd_leds,
> -						 cdev);
> +	struct asus_kbd_leds *led = container_of(listener, struct asus_kbd_leds,
> +						 listener);
>  	unsigned long flags;
>  
>  	spin_lock_irqsave(&led->lock, flags);
> @@ -509,20 +509,6 @@ static void asus_kbd_backlight_set(struct led_classdev *led_cdev,
>  	asus_schedule_work(led);
>  }
>  
> -static enum led_brightness asus_kbd_backlight_get(struct led_classdev *led_cdev)
> -{
> -	struct asus_kbd_leds *led = container_of(led_cdev, struct asus_kbd_leds,
> -						 cdev);
> -	enum led_brightness brightness;
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&led->lock, flags);
> -	brightness = led->brightness;
> -	spin_unlock_irqrestore(&led->lock, flags);
> -
> -	return brightness;
> -}
> -
>  static void asus_kbd_backlight_work(struct work_struct *work)
>  {
>  	struct asus_kbd_leds *led = container_of(work, struct asus_kbd_leds, work);
> @@ -539,34 +525,6 @@ static void asus_kbd_backlight_work(struct work_struct *work)
>  		hid_err(led->hdev, "Asus failed to set keyboard backlight: %d\n", ret);
>  }
>  
> -/* WMI-based keyboard backlight LED control (via asus-wmi driver) takes
> - * precedence. We only activate HID-based backlight control when the
> - * WMI control is not available.
> - */
> -static bool asus_kbd_wmi_led_control_present(struct hid_device *hdev)
> -{
> -	struct asus_drvdata *drvdata = hid_get_drvdata(hdev);
> -	u32 value;
> -	int ret;
> -
> -	if (!IS_ENABLED(CONFIG_ASUS_WMI))
> -		return false;
> -
> -	if (drvdata->quirks & QUIRK_ROG_NKEY_KEYBOARD &&
> -			dmi_check_system(asus_use_hid_led_dmi_ids)) {
> -		hid_info(hdev, "using HID for asus::kbd_backlight\n");
> -		return false;
> -	}
> -
> -	ret = asus_wmi_evaluate_method(ASUS_WMI_METHODID_DSTS,
> -				       ASUS_WMI_DEVID_KBD_BACKLIGHT, 0, &value);
> -	hid_dbg(hdev, "WMI backlight check: rc %d value %x", ret, value);
> -	if (ret)
> -		return false;
> -
> -	return !!(value & ASUS_WMI_DSTS_PRESENCE_BIT);
> -}
> -
>  /*
>   * We don't care about any other part of the string except the version section.
>   * Example strings: FGA80100.RC72LA.312_T01, FGA80100.RC71LS.318_T01
> @@ -701,14 +659,11 @@ static int asus_kbd_register_leds(struct hid_device *hdev)
>  	drvdata->kbd_backlight->removed = false;
>  	drvdata->kbd_backlight->brightness = 0;
>  	drvdata->kbd_backlight->hdev = hdev;
> -	drvdata->kbd_backlight->cdev.name = "asus::kbd_backlight";
> -	drvdata->kbd_backlight->cdev.max_brightness = 3;
> -	drvdata->kbd_backlight->cdev.brightness_set = asus_kbd_backlight_set;
> -	drvdata->kbd_backlight->cdev.brightness_get = asus_kbd_backlight_get;
> +	drvdata->kbd_backlight->listener.brightness_set = asus_kbd_backlight_set;
>  	INIT_WORK(&drvdata->kbd_backlight->work, asus_kbd_backlight_work);
>  	spin_lock_init(&drvdata->kbd_backlight->lock);
>  
> -	ret = devm_led_classdev_register(&hdev->dev, &drvdata->kbd_backlight->cdev);
> +	ret = asus_hid_register_listener(&drvdata->kbd_backlight->listener);
>  	if (ret < 0) {
>  		/* No need to have this still around */
>  		devm_kfree(&hdev->dev, drvdata->kbd_backlight);
> @@ -1105,7 +1060,7 @@ static int __maybe_unused asus_resume(struct hid_device *hdev) {
>  
>  	if (drvdata->kbd_backlight) {
>  		const u8 buf[] = { FEATURE_KBD_REPORT_ID, 0xba, 0xc5, 0xc4,
> -				drvdata->kbd_backlight->cdev.brightness };
> +				drvdata->kbd_backlight->brightness };
>  		ret = asus_kbd_set_report(hdev, buf, sizeof(buf));
>  		if (ret < 0) {
>  			hid_err(hdev, "Asus failed to set keyboard backlight: %d\n", ret);
> @@ -1241,7 +1196,6 @@ static int asus_probe(struct hid_device *hdev, const struct hid_device_id *id)
>  	}
>  
>  	if (is_vendor && (drvdata->quirks & QUIRK_USE_KBD_BACKLIGHT) &&
> -	    !asus_kbd_wmi_led_control_present(hdev) &&
>  	    asus_kbd_register_leds(hdev))
>  		hid_warn(hdev, "Failed to initialize backlight.\n");
>  
> @@ -1282,6 +1236,8 @@ static void asus_remove(struct hid_device *hdev)
>  	unsigned long flags;
>  
>  	if (drvdata->kbd_backlight) {
> +		asus_hid_unregister_listener(&drvdata->kbd_backlight->listener);
> +
>  		spin_lock_irqsave(&drvdata->kbd_backlight->lock, flags);
>  		drvdata->kbd_backlight->removed = true;
>  		spin_unlock_irqrestore(&drvdata->kbd_backlight->lock, flags);