mirros/rockchip-kernel
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

backlight: Expose brightness curve type through sysfs

Browse Source 
Backlight brightness curves can have different shapes. The two main
types are linear and non-linear curves. The human eye doesn't
perceive linearly increasing/decreasing brightness as linear (see
also 88ba95bedb "backlight: pwm_bl: Compute brightness of LED
linearly to human eye"), hence many backlights use non-linear (often
logarithmic) brightness curves. The type of curve currently is opaque
to userspace, so userspace often uses more or less reliable heuristics
(like the number of brightness levels) to decide whether to treat a
backlight device as linear or non-linear.

Export the type of the brightness curve via the new sysfs attribute
'scale'. The value of the attribute can be 'linear', 'non-linear' or
'unknown'. For devices that don't provide information about the scale
of their brightness curve the value of the 'scale' attribute is 'unknown'.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Matthias Kaehlcke
2019-07-09 12:00:05 -07:00
committed by Lee Jones
parent 6451e123de
commit d55c028f8b
4 changed files with 54 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/linux/backlight.h
View File

@@ -46,6 +46,12 @@ enum backlight_notification {
BACKLIGHT_UNREGISTERED,
};
enum backlight_scale {
BACKLIGHT_SCALE_UNKNOWN = 0,
BACKLIGHT_SCALE_LINEAR,
BACKLIGHT_SCALE_NON_LINEAR,
};
struct backlight_device;
struct fb_info;
@@ -80,6 +86,8 @@ struct backlight_properties {
enum backlight_type type;
/* Flags used to signal drivers of state changes */
unsigned int state;
/* Type of the brightness scale (linear, non-linear, ...) */
enum backlight_scale scale;
#define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */
#define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */