On 11/07/2013 06:04 AM, Rafael J. Wysocki wrote: > On Wednesday, November 06, 2013 09:07:10 AM Aaron Lu wrote: >> 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. >> >> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=64031 >> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=61231 >> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=63111 >> Reported-by: Qingshuai Tian <qingshuai.tian@xxxxxxxxx> >> Tested-by: Aaron Lu <aaron.lu@xxxxxxxxx> on "Idealpad u330p" >> Reported-and-tested-by: <erno@xxxxxx> on "Acer Aspire V5-573G" >> Reported-and-tested-by: Kirill Tkhai <tkhai@xxxxxxxxx> on "HP 250 G1" >> Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> >> Cc: stable <stable@xxxxxxxxxxxxxxx> > > All stable, or any particular series? All stable. Thanks, Aaron > >> --- >> drivers/acpi/video.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c >> index bf521b36c2f9..a049fa9360d0 100644 >> --- a/drivers/acpi/video.c >> +++ b/drivers/acpi/video.c >> @@ -858,7 +858,7 @@ acpi_video_init_brightness(struct acpi_video_device *device) >> for (i = 2; i < br->count; i++) >> if (level == br->levels[i]) >> break; >> - if (i == br->count) >> + if (i == br->count || !level) >> level = max_level; >> } >> >> -- 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
