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>
--
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);
/*
--
1.9.0
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
