linux-kernel - Re: [PATCH] platform/x86: dell-laptop: Filter out spurious keyboard backlight change events

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Date:   Fri, 5 Jan 2018 12:40:04 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Pali Rohár <pali.rohar@...il.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: dell-laptop: Filter out spurious keyboard
 backlight change events

On Thu, Jan 4, 2018 at 10:52 AM, Hans de Goede <hdegoede@...hat.com> wrote:
> On some Dell XPS models WMI events of type 0x0000 reporting a keycode of
> 0xe00c get reported when the brightness of the LCD panel changes.
>
> This leads to us reporting false-positive kbd_led change events to
> userspace which in turn leads to the kbd backlight OSD showing when it
> should not.
>
> We already read the current keyboard backlight brightness value when
> reporting events because the led_classdev_notify_brightness_hw_changed
> API requires this. Compare this value to the last known value and filter
> out duplicate events, fixing this.
>
> Note the fixed issue is esp. a problem on XPS models with an ambient light
> sensor and automatic brightness adjustments turned on, this causes the kbd
> backlight OSD to show all the time there.
>

Should it have Fixes tag?

Pali, any comment on this?

> BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1514969
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
> ---
>  drivers/platform/x86/dell-laptop.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
> index cd4725e7e0b5..2ef3297a9efc 100644
> --- a/drivers/platform/x86/dell-laptop.c
> +++ b/drivers/platform/x86/dell-laptop.c
> @@ -1133,6 +1133,7 @@ static u8 kbd_previous_mode_bit;
>
>  static bool kbd_led_present;
>  static DEFINE_MUTEX(kbd_led_mutex);
> +static enum led_brightness kbd_led_level;
>
>  /*
>   * NOTE: there are three ways to set the keyboard backlight level.
> @@ -1947,6 +1948,7 @@ static enum led_brightness kbd_led_level_get(struct led_classdev *led_cdev)
>  static int kbd_led_level_set(struct led_classdev *led_cdev,
>                              enum led_brightness value)
>  {
> +       enum led_brightness new_value = value;
>         struct kbd_state state;
>         struct kbd_state new_state;
>         u16 num;
> @@ -1976,6 +1978,9 @@ static int kbd_led_level_set(struct led_classdev *led_cdev,
>         }
>
>  out:
> +       if (ret == 0)
> +               kbd_led_level = new_value;
> +
>         mutex_unlock(&kbd_led_mutex);
>         return ret;
>  }
> @@ -2003,6 +2008,9 @@ static int __init kbd_led_init(struct device *dev)
>                 if (kbd_led.max_brightness)
>                         kbd_led.max_brightness--;
>         }
> +
> +       kbd_led_level = kbd_led_level_get(NULL);
> +
>         ret = led_classdev_register(dev, &kbd_led);
>         if (ret)
>                 kbd_led_present = false;
> @@ -2027,13 +2035,25 @@ static void kbd_led_exit(void)
>  static int dell_laptop_notifier_call(struct notifier_block *nb,
>                                      unsigned long action, void *data)
>  {
> +       bool changed = false;
> +       enum led_brightness new_kbd_led_level;
> +
>         switch (action) {
>         case DELL_LAPTOP_KBD_BACKLIGHT_BRIGHTNESS_CHANGED:
>                 if (!kbd_led_present)
>                         break;
>
> -               led_classdev_notify_brightness_hw_changed(&kbd_led,
> -                                               kbd_led_level_get(&kbd_led));
> +               mutex_lock(&kbd_led_mutex);
> +               new_kbd_led_level = kbd_led_level_get(&kbd_led);
> +               if (kbd_led_level != new_kbd_led_level) {
> +                       kbd_led_level = new_kbd_led_level;
> +                       changed = true;
> +               }
> +               mutex_unlock(&kbd_led_mutex);
> +
> +               if (changed)
> +                       led_classdev_notify_brightness_hw_changed(&kbd_led,
> +                                                               kbd_led_level);
>                 break;
>         }
>
> --
> 2.14.3
>



-- 
With Best Regards,
Andy Shevchenko