On Friday, August 02, 2013 02:37:09 PM Felipe Contreras wrote: > If the _BCL package is descending, the first level (br->levels[2]) will > 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. But if > the _BCL package 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). > > Signed-off-by: Felipe Contreras <felipe.contreras@xxxxxxxxx> Looks reasonable. Aaron, what do you think? Rafael > --- > > On top of this we might want to test yet another value, because br->levels[3] > might be the current value (although very unlikely). > > 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 0ec434d..e1284b8 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) > -- 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
