Message-ID: 
 <CAGwozwGBt0tae2oqXAjigpoFYWTfhdUC0Jg5toggE8=kn4ghRQ@mail.gmail.com>
Date: Thu, 20 Nov 2025 15:40:49 +0100
From: Antheas Kapenekakis <lkml@...heas.dev>
To: Denis Benato <benato.denis96@...il.com>
Cc: platform-driver-x86@...r.kernel.org, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jiri Kosina <jikos@...nel.org>,
	Benjamin Tissoires <bentiss@...nel.org>,
 Corentin Chary <corentin.chary@...il.com>,
	"Luke D . Jones" <luke@...nes.dev>, Hans de Goede <hansg@...nel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v9 07/11] platform/x86: asus-wmi: Add support for multiple
 kbd led handlers

On Thu, 20 Nov 2025 at 14:46, Denis Benato <benato.denis96@...il.com> wrote:
>
>
> On 11/20/25 10:46, Antheas Kapenekakis wrote:
> > Some devices, such as the Z13 have multiple Aura devices connected
> > to them by USB. In addition, they might have a WMI interface for
> > RGB. In Windows, Armoury Crate exposes a unified brightness slider
> > for all of them, with 3 brightness levels.
> >
> > Therefore, to be synergistic in Linux, and support existing tooling
> > such as UPower, allow adding listeners to the RGB device of the WMI
> > interface. If WMI does not exist, lazy initialize the interface.
> >
> > Since hid-asus and asus-wmi can both interact with the led objects
> > including from an atomic context, protect the brightness access with a
> > spinlock and update the values from a workqueue. Use this workqueue to
> > also process WMI keyboard events, so they are handled asynchronously.
> >
> > Signed-off-by: Antheas Kapenekakis <lkml@...heas.dev>
> > ---
> >  drivers/platform/x86/asus-wmi.c            | 174 ++++++++++++++++++---
> >  include/linux/platform_data/x86/asus-wmi.h |  17 ++
> >  2 files changed, 167 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
> > index e72a2b5d158e..5f23aedbf34f 100644
> > --- a/drivers/platform/x86/asus-wmi.c
> > +++ b/drivers/platform/x86/asus-wmi.c
> > @@ -36,6 +36,7 @@
> >  #include <linux/rfkill.h>
> >  #include <linux/seq_file.h>
> >  #include <linux/slab.h>
> > +#include <linux/spinlock.h>
> >  #include <linux/types.h>
> >  #include <linux/units.h>
> >
> > @@ -258,6 +259,9 @@ struct asus_wmi {
> >       int tpd_led_wk;
> >       struct led_classdev kbd_led;
> >       int kbd_led_wk;
> > +     bool kbd_led_notify;
> > +     bool kbd_led_avail;
> > +     bool kbd_led_registered;
> >       struct led_classdev lightbar_led;
> >       int lightbar_led_wk;
> >       struct led_classdev micmute_led;
> > @@ -266,6 +270,7 @@ struct asus_wmi {
> >       struct work_struct tpd_led_work;
> >       struct work_struct wlan_led_work;
> >       struct work_struct lightbar_led_work;
> > +     struct work_struct kbd_led_work;
> >
> >       struct asus_rfkill wlan;
> >       struct asus_rfkill bluetooth;
> > @@ -1530,6 +1535,99 @@ static void asus_wmi_battery_exit(struct asus_wmi *asus)
> >
> >  /* LEDs ***********************************************************************/
> >
> > +struct asus_hid_ref {
> > +     struct list_head listeners;
> > +     struct asus_wmi *asus;
> > +     /* Protects concurrent access from hid-asus and asus-wmi to leds */
> > +     spinlock_t lock;
> > +};
> > +
> > +static struct asus_hid_ref asus_ref = {
> > +     .listeners = LIST_HEAD_INIT(asus_ref.listeners),
> > +     .asus = NULL,
> > +     /*
> > +      * Protects .asus, .asus.kbd_led_{wk,notify}, and .listener refs. Other
> > +      * asus variables are read-only after .asus is set. Except the led cdev
> > +      * device if not kbd_led_avail. That becomes read-only after the
> > +      * first hid-asus listener registers and triggers the work queue. It is
> > +      * then not referenced again until unregistering, which happens after
> > +      * .asus ref is dropped. Since .asus needs to be accessed by hid-asus
> > +      * IRQs to check if forwarding events is possible, a spinlock is used.
> > +      */
> What are "That" and "It" referring to in this context?
>
> Are you absolutely sure you want to begin a sentence with "Except"?

I think it is pretty clear that both of them refer to the led cdev
device. Phrasing could be a bit better but it is not ambiguous.

> On "ref is dropped" I would continue with ": since .asus .....".

Add spaces in-between your replies, these are easy to miss.

Since... is a separate sentence and its meaning is correct. It should
not be chained with the first sentence.

Essentially, this paragraph says three things: 1) .asus,
.asus.kbd_led_{wk,notify}, and .listener refs are protected by the
spinlock. 2) the led cdev is not, because it is either initialized
during probe before asus.ref is registered so hid-asus cannot touch it
or in the workqueue (if not kbd_led_avail) which is single threaded
and guaranteed to continue until asus-wmi touches that variable again
because it will have destroyed the workqueue first. 3) A spinlock is
used because these variables are accessed in an IRQ context.

> > +     .lock = __SPIN_LOCK_UNLOCKED(asus_ref.lock),
> > +};
> > +
> > +/*
> > + * Allows registering hid-asus listeners that want to be notified of
> > + * keyboard backlight changes.
> > + */
> > +int asus_hid_register_listener(struct asus_hid_listener *bdev)
> > +{
> > +     struct asus_wmi *asus;
> > +
> > +     guard(spinlock_irqsave)(&asus_ref.lock);
> > +     list_add_tail(&bdev->list, &asus_ref.listeners);
> > +     asus = asus_ref.asus;
> > +     if (asus)
> > +             queue_work(asus->led_workqueue, &asus->kbd_led_work);
> Are you sure this has to be protected by the guard too?

Yes. After you get a reference to asus_ref.asus you need to hold a
spinlock until it is dropped so asus-wmi is not able to exit or mutate
itself.

For the same reason, the workqueue can be triggered by both asus-wmi
and multiple hid-asus devices, so it needs to be bound as well.

> > +     return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(asus_hid_register_listener);
> > +
> > +/*
> > + * Allows unregistering hid-asus listeners that were added with
> > + * asus_hid_register_listener().
> > + */
> > +void asus_hid_unregister_listener(struct asus_hid_listener *bdev)
> > +{
> > +     guard(spinlock_irqsave)(&asus_ref.lock);
> > +     list_del(&bdev->list);
> > +}
> > +EXPORT_SYMBOL_GPL(asus_hid_unregister_listener);
> > +
> > +static void do_kbd_led_set(struct led_classdev *led_cdev, int value);
> > +
> > +static void kbd_led_update_all(struct work_struct *work)
> > +{
> > +     struct asus_wmi *asus;
> > +     bool registered, notify;
> > +     int ret, value;
> > +
> > +     asus = container_of(work, struct asus_wmi, kbd_led_work);
> > +
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock) {
> > +             registered = asus->kbd_led_registered;
> > +             value = asus->kbd_led_wk;
> > +             notify = asus->kbd_led_notify;
> > +     }
> > +
> > +     if (!registered) {
> > +             /*
> > +              * This workqueue runs under asus-wmi, which means probe has
> > +              * completed and asus-wmi will keep running until it finishes.
> > +              * Therefore, we can safely register the LED without holding
> > +              * a spinlock.
> > +              */
> > +             ret = devm_led_classdev_register(&asus->platform_device->dev,
> > +                                         &asus->kbd_led);
> > +             if (!ret) {
> > +                     scoped_guard(spinlock_irqsave, &asus_ref.lock)
> > +                             asus->kbd_led_registered = true;
> > +             } else {
> > +                     pr_warn("Failed to register keyboard backlight LED: %d\n", ret);
> > +                     return;
> > +             }
> > +     }
> > +
> > +     if (value >= 0)
> > +             do_kbd_led_set(&asus->kbd_led, value);
> > +     if (notify) {
> > +             scoped_guard(spinlock_irqsave, &asus_ref.lock)
> > +                     asus->kbd_led_notify = false;
> > +             led_classdev_notify_brightness_hw_changed(&asus->kbd_led, value);
> > +     }
> > +}
> > +
> >  /*
> >   * These functions actually update the LED's, and are called from a
> >   * workqueue. By doing this as separate work rather than when the LED
> > @@ -1576,7 +1674,8 @@ static void kbd_led_update(struct asus_wmi *asus)
> >  {
> >       int ctrl_param = 0;
> >
> > -     ctrl_param = 0x80 | (asus->kbd_led_wk & 0x7F);
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock)
> > +             ctrl_param = 0x80 | (asus->kbd_led_wk & 0x7F);
> >       asus_wmi_set_devstate(ASUS_WMI_DEVID_KBD_BACKLIGHT, ctrl_param, NULL);
> >  }
> >
> > @@ -1609,14 +1708,23 @@ static int kbd_led_read(struct asus_wmi *asus, int *level, int *env)
> >
> >  static void do_kbd_led_set(struct led_classdev *led_cdev, int value)
> >  {
> > +     struct asus_hid_listener *listener;
> >       struct asus_wmi *asus;
> >       int max_level;
> >
> >       asus = container_of(led_cdev, struct asus_wmi, kbd_led);
> >       max_level = asus->kbd_led.max_brightness;
> >
> > -     asus->kbd_led_wk = clamp_val(value, 0, max_level);
> > -     kbd_led_update(asus);
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock)
> > +             asus->kbd_led_wk = clamp_val(value, 0, max_level);
> > +
> > +     if (asus->kbd_led_avail)
> > +             kbd_led_update(asus);
> > +
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock) {
> > +             list_for_each_entry(listener, &asus_ref.listeners, list)
> > +                     listener->brightness_set(listener, asus->kbd_led_wk);
> > +     }
> >  }
> >
> >  static void kbd_led_set(struct led_classdev *led_cdev,
> > @@ -1631,10 +1739,11 @@ static void kbd_led_set(struct led_classdev *led_cdev,
> >
> >  static void kbd_led_set_by_kbd(struct asus_wmi *asus, enum led_brightness value)
> >  {
> > -     struct led_classdev *led_cdev = &asus->kbd_led;
> > -
> > -     do_kbd_led_set(led_cdev, value);
> > -     led_classdev_notify_brightness_hw_changed(led_cdev, asus->kbd_led_wk);
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock) {
> > +             asus->kbd_led_wk = value;
> > +             asus->kbd_led_notify = true;
> > +     }
> > +     queue_work(asus->led_workqueue, &asus->kbd_led_work);
> >  }
> >
> >  static enum led_brightness kbd_led_get(struct led_classdev *led_cdev)
> > @@ -1644,10 +1753,18 @@ static enum led_brightness kbd_led_get(struct led_classdev *led_cdev)
> >
> >       asus = container_of(led_cdev, struct asus_wmi, kbd_led);
> >
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock) {
> > +             if (!asus->kbd_led_avail)
> > +                     return asus->kbd_led_wk;
> > +     }
> > +
> >       retval = kbd_led_read(asus, &value, NULL);
> >       if (retval < 0)
> >               return retval;
> >
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock)
> > +             asus->kbd_led_wk = value;
> > +
> >       return value;
> >  }
> >
> > @@ -1759,7 +1876,9 @@ static int camera_led_set(struct led_classdev *led_cdev,
> >
> >  static void asus_wmi_led_exit(struct asus_wmi *asus)
> >  {
> > -     led_classdev_unregister(&asus->kbd_led);
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock)
> > +             asus_ref.asus = NULL;
> > +
> >       led_classdev_unregister(&asus->tpd_led);
> >       led_classdev_unregister(&asus->wlan_led);
> >       led_classdev_unregister(&asus->lightbar_led);
> > @@ -1797,22 +1916,25 @@ static int asus_wmi_led_init(struct asus_wmi *asus)
> >                       goto error;
> >       }
> >
> > -     if (!kbd_led_read(asus, &led_val, NULL) && !dmi_check_system(asus_use_hid_led_dmi_ids)) {
> > -             pr_info("using asus-wmi for asus::kbd_backlight\n");
> > -             asus->kbd_led_wk = led_val;
> > -             asus->kbd_led.name = "asus::kbd_backlight";
> > -             asus->kbd_led.flags = LED_BRIGHT_HW_CHANGED;
> > -             asus->kbd_led.brightness_set = kbd_led_set;
> > -             asus->kbd_led.brightness_get = kbd_led_get;
> > -             asus->kbd_led.max_brightness = 3;
> > +     asus->kbd_led.name = "asus::kbd_backlight";
> > +     asus->kbd_led.flags = LED_BRIGHT_HW_CHANGED;
> > +     asus->kbd_led.brightness_set = kbd_led_set;
> > +     asus->kbd_led.brightness_get = kbd_led_get;
> > +     asus->kbd_led.max_brightness = 3;
> > +     asus->kbd_led_avail = !kbd_led_read(asus, &led_val, NULL);
> > +     INIT_WORK(&asus->kbd_led_work, kbd_led_update_all);
> >
> > +     if (asus->kbd_led_avail) {
> > +             asus->kbd_led_wk = led_val;
> >               if (num_rgb_groups != 0)
> >                       asus->kbd_led.groups = kbd_rgb_mode_groups;
> > +     } else
> > +             asus->kbd_led_wk = -1;
> >
> > -             rv = led_classdev_register(&asus->platform_device->dev,
> > -                                        &asus->kbd_led);
> > -             if (rv)
> > -                     goto error;
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock) {
> > +             asus_ref.asus = asus;
> > +             if (asus->kbd_led_avail || !list_empty(&asus_ref.listeners))
> > +                     queue_work(asus->led_workqueue, &asus->kbd_led_work);
> >       }
> >
> >       if (asus_wmi_dev_is_present(asus, ASUS_WMI_DEVID_WIRELESS_LED)
> > @@ -4272,6 +4394,7 @@ static int asus_wmi_get_event_code(union acpi_object *obj)
> >
> >  static void asus_wmi_handle_event_code(int code, struct asus_wmi *asus)
> >  {
> > +     enum led_brightness led_value;
> >       unsigned int key_value = 1;
> >       bool autorelease = 1;
> >
> > @@ -4288,19 +4411,22 @@ static void asus_wmi_handle_event_code(int code, struct asus_wmi *asus)
> >               return;
> >       }
> >
> > +     scoped_guard(spinlock_irqsave, &asus_ref.lock)
> > +             led_value = asus->kbd_led_wk;
> > +
> >       if (code == NOTIFY_KBD_BRTUP) {
> > -             kbd_led_set_by_kbd(asus, asus->kbd_led_wk + 1);
> > +             kbd_led_set_by_kbd(asus, led_value + 1);
> >               return;
> >       }
> >       if (code == NOTIFY_KBD_BRTDWN) {
> > -             kbd_led_set_by_kbd(asus, asus->kbd_led_wk - 1);
> > +             kbd_led_set_by_kbd(asus, led_value - 1);
> >               return;
> >       }
> >       if (code == NOTIFY_KBD_BRTTOGGLE) {
> > -             if (asus->kbd_led_wk == asus->kbd_led.max_brightness)
> > +             if (led_value == asus->kbd_led.max_brightness)
> >                       kbd_led_set_by_kbd(asus, 0);
> >               else
> > -                     kbd_led_set_by_kbd(asus, asus->kbd_led_wk + 1);
> > +                     kbd_led_set_by_kbd(asus, led_value + 1);
> >               return;
> >       }
> >
> > diff --git a/include/linux/platform_data/x86/asus-wmi.h b/include/linux/platform_data/x86/asus-wmi.h
> > index 8a515179113d..1165039013b1 100644
> > --- a/include/linux/platform_data/x86/asus-wmi.h
> > +++ b/include/linux/platform_data/x86/asus-wmi.h
> > @@ -163,11 +163,20 @@ enum asus_ally_mcu_hack {
> >       ASUS_WMI_ALLY_MCU_HACK_DISABLED,
> >  };
> >
> > +/* Used to notify hid-asus when asus-wmi changes keyboard backlight */
> > +struct asus_hid_listener {
> > +     struct list_head list;
> > +     void (*brightness_set)(struct asus_hid_listener *listener, int brightness);
> > +};
> > +
> >  #if IS_REACHABLE(CONFIG_ASUS_WMI)
> >  void set_ally_mcu_hack(enum asus_ally_mcu_hack status);
> >  void set_ally_mcu_powersave(bool enabled);
> >  int asus_wmi_set_devstate(u32 dev_id, u32 ctrl_param, u32 *retval);
> >  int asus_wmi_evaluate_method(u32 method_id, u32 arg0, u32 arg1, u32 *retval);
> > +
> > +int asus_hid_register_listener(struct asus_hid_listener *cdev);
> > +void asus_hid_unregister_listener(struct asus_hid_listener *cdev);
> >  #else
> >  static inline void set_ally_mcu_hack(enum asus_ally_mcu_hack status)
> >  {
> > @@ -184,6 +193,14 @@ static inline int asus_wmi_evaluate_method(u32 method_id, u32 arg0, u32 arg1,
> >  {
> >       return -ENODEV;
> >  }
> > +
> > +static inline int asus_hid_register_listener(struct asus_hid_listener *bdev)
> > +{
> > +     return -ENODEV;
> > +}
> > +static inline void asus_hid_unregister_listener(struct asus_hid_listener *bdev)
> > +{
> > +}
> >  #endif
> >
> >  /* To be used by both hid-asus and asus-wmi to determine which controls kbd_brightness */
>

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