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

Antheas Kapenekakis
2025-10-13T21:57:34Z

On Mon, 13 Oct 2025 at 23:44, Denis Benato <benato.denis96@gmail.com> wrote:
>
>
> 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?

You can reference the V1 description [1]

[1] https://lore.kernel.org/all/20250319191320.10092-1-lkml@antheas.dev/

> >
> > 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?

A listener is the handle that is passed to asus-wmi so that it can
communicate with hid-asus. Since the flow of communication flows from
asus-wmi -> hid-asus, the pointer is placed on asus-wmi.

The boolean kbd_led_avail is used to signify whether the BIOS supports
RGB commands. If not, we still want the common handler to be there to
link multiple hid-asus devices together. At the same time, we need to
skip calling the bios commands for brightness, and hold a value for
the previous brightness outside the bios.

The kbd_led_registered fixes the race condition that happens between
hid-asus and asus-wmi. Specifically, it ensures that the rgb listener
is only setup once, either once asus-wmi loads (if it supports RGB) or
when the first hid device loads.

Best,
Antheas

> > 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);
>