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| author |   Felipe Contreras <felipe.contreras@gmail.com> | 2013-08-03 23:00:25 +0200 |
|---|---|---|
| committer |   Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2013-08-04 23:45:39 +0200 |
| commit | b3b301c5fed8a0868e56c98b922cb0c881b3857d (patch) | |
| tree | add3a807e37d55993d7ae9ea74fff062dae5da32 /drivers/acpi | |
| parent | Linux 3.11-rc4 (diff) | |
| download | linux-dev-b3b301c5fed8a0868e56c98b922cb0c881b3857d.tar.xz linux-dev-b3b301c5fed8a0868e56c98b922cb0c881b3857d.zip | |
ACPI / video: improve quirk check in acpi_video_bqc_quirk()
If the _BCL package ordering is descending, the first level
(br->levels[2]) is likely to be 0, and if the number of levels
matches the number of steps, we might confuse a returned level to
mean the index.
For example:
current_level = max_level = 100
test_level = 0
returned level = 100
In this case 100 means the level, not the index, and _BCM failed.
Still, if the _BCL package ordering is descending, the index of
level 0 is also 100, so we assume _BQC is indexed, when it's not.
This causes all _BQC calls to return bogus values causing weird
behavior from the user's perspective. For example:
xbacklight -set 10; xbacklight -set 20;
would flash to 90% and then slowly down to the desired level (20).
The solution is simple; test anything other than the first level
(e.g. 1).
[rjw: Changelog]
Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi')
| -rw-r--r-- | drivers/acpi/video.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c index 0ec434d2586d..e1284b8dc6ee 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -689,7 +689,7 @@ static int acpi_video_bqc_quirk(struct acpi_video_device *device, * Some systems always report current brightness level as maximum * through _BQC, we need to test another value for them. */ - test_level = current_level == max_level ? br->levels[2] : max_level; + test_level = current_level == max_level ? br->levels[3] : max_level; result = acpi_video_device_lcd_set_level(device, test_level); if (result) |