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? > --- > 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; > } > > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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
