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authorAaron Lu <aaron.lu@intel.com>2013-11-06 09:07:10 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-11-29 11:11:43 -0800
commit602b910bb0b18c5d7887df7a05e256fac780cf49 (patch)
tree43160bc953b4e48ef3b6d114f1793a5620f8b2e3 /drivers/acpi
parent968f56ccc37ae686e226fbd2cec9b826c4b6f7c4 (diff)
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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.c2
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;
}