On Tuesday, May 06, 2014 02:46:23 PM Hans de Goede wrote:
> acpi-video is unique in that it not only generates brightness up/down
> keypresses, but also (sometimes) actively changes the brightness itself.
>
> This presents an inconsistent kernel interface to userspace, basically there
> are 2 different scenarios, depending on the laptop model:
>
> 1) On some laptops a brightness up/down keypress means: show a brightness osd
> with the current brightness, iow it is a brightness has changed notification.
>
> 2) Where as on (a lot of) other laptops it means a brightness up/down key was
> pressed, deal with it.
>
> Most of the desktop environments interpret any press as in scenario 2, and
> change the brightness up / down as a response to the key events, causing it
> to be changed twice, once by acpi-video and once by the DE.
>
> With the new default for video.use_native_backlight we will be moving even
> more laptops over to behaving as in scenario 2. Making the remaining laptops
> even more of a weird exception. Also note that it is hard to detect scenario
> 1 properly in userspace, and AFAIK none of the DE-s deals with it.
>
> Therefor this commit changes the default of brightness_switch_enabled to 0
> making its behavior consistent with all the other backlight drivers.
>
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> Reviewed-by: Aaron Lu <aaron.lu@xxxxxxxxx>
I've queued this up for 3.16, thanks!
> --
>
> Changes in v2:
> Also update Documentation/kernel-parameters.txt for the new default.
> ---
> Documentation/kernel-parameters.txt | 2 +-
> drivers/acpi/video.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 4384217..cc2c243 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -3461,7 +3461,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> the allocated input device; If set to 0, video driver
> will only send out the event without touching backlight
> brightness level.
> - default: 1
> + default: 0
>
> virtio_mmio.device=
> [VMMIO] Memory mapped virtio (platform) device.
> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> index cebc74d..34198b2 100644
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -68,7 +68,7 @@ MODULE_AUTHOR("Bruno Ducrot");
> MODULE_DESCRIPTION("ACPI Video Driver");
> MODULE_LICENSE("GPL");
>
> -static bool brightness_switch_enabled = 1;
> +static bool brightness_switch_enabled;
> module_param(brightness_switch_enabled, bool, 0644);
>
> /*
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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