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ACPI / video: change acpi-video brightness_switch_enabled default to 0 

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@redhat.com>
Reviewed-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
hifive-unleashed-5.1
Hans de Goede 2014-05-06 14:46:23 +02:00 committed by Rafael J. Wysocki
parent 43d9490244
commit 886129a8ee
2 changed files with 2 additions and 2 deletions
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2
Documentation/kernel-parameters.txt
View File

@ -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.

2
drivers/acpi/video.c
View File

@ -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);
/*