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SubjectRe: [PATCH] Rationalise ACPI backlight implementation
Date
On Tuesday 25 December 2007 21:03, Matthew Garrett wrote:
> The sysfs backlight class provides no mechanism for querying the
> acceptable brightness for a backlight. The ACPI spec states that values
> are only valid if they are reported as available by the firmware. Since
> we can't provide that information to userspace, instead collapse the
> range to the number of actual values that can be set.
>
> Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>

I wish we did this in the first place.
But doing it now is an API change -- since
with the old way 100 always meant 100% brightness, yes?

so my concern is that if we change what "10" means, somebody like akpm
with an existing script gets grumpy.

-Len

> ---
>
> diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
> index 521645e..12b2adb 100644
> --- a/drivers/acpi/video.c
> +++ b/drivers/acpi/video.c
> @@ -296,18 +296,26 @@ static int acpi_video_device_set_state(struct acpi_video_device *device, int sta
> static int acpi_video_get_brightness(struct backlight_device *bd)
> {
> unsigned long cur_level;
> + int i;
> struct acpi_video_device *vd =
> (struct acpi_video_device *)bl_get_data(bd);
> acpi_video_device_lcd_get_level_current(vd, &cur_level);
> - return (int) cur_level;
> + for (i=2; i<vd->brightness->count; i++) {
> + if (vd->brightness->levels[i] == cur_level)
> + /* The first two entries are special - see page 575
> + of the ACPI spec 3.0 */
> + return i-2;
> + }
> + return 0;
> }
>
> static int acpi_video_set_brightness(struct backlight_device *bd)
> {
> - int request_level = bd->props.brightness;
> + int request_level = bd->props.brightness+2;
> struct acpi_video_device *vd =
> (struct acpi_video_device *)bl_get_data(bd);
> - acpi_video_device_lcd_set_level(vd, request_level);
> + acpi_video_device_lcd_set_level(vd,
> + vd->brightness->levels[request_level]);
> return 0;
> }
>
> @@ -656,7 +664,6 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
> kfree(obj);
>
> if (device->cap._BCL && device->cap._BCM && device->cap._BQC && max_level > 0){
> - unsigned long tmp;
> static int count = 0;
> char *name;
> name = kzalloc(MAX_NAME_LEN, GFP_KERNEL);
> @@ -664,11 +671,10 @@ static void acpi_video_device_find_cap(struct acpi_video_device *device)
> return;
>
> sprintf(name, "acpi_video%d", count++);
> - acpi_video_device_lcd_get_level_current(device, &tmp);
> device->backlight = backlight_device_register(name,
> NULL, device, &acpi_backlight_ops);
> - device->backlight->props.max_brightness = max_level;
> - device->backlight->props.brightness = (int)tmp;
> + device->backlight->props.max_brightness = device->brightness->count-3;
> + device->backlight->props.brightness = acpi_video_get_brightness(device->backlight);
> backlight_update_status(device->backlight);
>
> kfree(name);
>


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