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| author | Aaron Lu <aaron.lu@intel.com> | 2013-11-06 09:07:10 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-11-29 11:11:43 -0800 |
| commit | 602b910bb0b18c5d7887df7a05e256fac780cf49 (patch) | |
| tree | 43160bc953b4e48ef3b6d114f1793a5620f8b2e3 /drivers/acpi | |
| parent | 968f56ccc37ae686e226fbd2cec9b826c4b6f7c4 (diff) | |
| download | linux-3.10-602b910bb0b18c5d7887df7a05e256fac780cf49.tar.gz linux-3.10-602b910bb0b18c5d7887df7a05e256fac780cf49.tar.bz2 linux-3.10-602b910bb0b18c5d7887df7a05e256fac780cf49.zip | |
ACPI / video: Quirk initial backlight level 0
commit 2c62333a408f5badd2d2ffd7177f95deeccc5ca4 upstream.
Some firmware doesn't initialize initial backlight level to a proper
value and _BQC will return 0 on first time evaluation. We used to be
able to detect such incorrect value with our code logic, as value 0
normally isn't a valid value in _BCL. But with the introduction of Win8,
firmware begins to fill _BCL with values from 0 to 100, now 0 becomes
a valid value but that value will make user's screen black. This patch
test initial _BQC for value 0, if such a value is returned, do not use
it.
References: https://bugzilla.kernel.org/show_bug.cgi?id=64031
References: https://bugzilla.kernel.org/show_bug.cgi?id=61231
References: https://bugzilla.kernel.org/show_bug.cgi?id=63111
Reported-by: Qingshuai Tian <qingshuai.tian@intel.com>
Tested-by: Aaron Lu <aaron.lu@intel.com> # on "Idealpad u330p"
Reported-and-tested-by: <erno@iki.fi> # on "Acer Aspire V5-573G"
Reported-and-tested-by: Kirill Tkhai <tkhai@yandex.ru> # on "HP 250 G1"
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 0e4b96b62c7..055dfdfd734 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -846,7 +846,7 @@ acpi_video_init_brightness(struct acpi_video_device *device) for (i = 2; i < br->count; i++) if (level_old == br->levels[i]) break; - if (i == br->count) + if (i == br->count || !level) level = max_level; } |