lkml.org 
[lkml]   [2013]   [Aug]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] acpi: video: improve quirk check
Date
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@gmail.com>

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.


\
 
 \ /
  Last update: 2013-08-03 02:01    [W:0.108 / U:17.560 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site