From 6451e123dec34e295cb0affcd48f671275bdb671 Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Tue, 9 Jul 2019 12:00:04 -0700 Subject: MAINTAINERS: Add entry for stable backlight sysfs ABI documentation Add an entry for the stable backlight sysfs ABI to the MAINTAINERS file. Signed-off-by: Matthias Kaehlcke Acked-by: Daniel Thompson Signed-off-by: Lee Jones --- MAINTAINERS | 1 + 1 file changed, 1 insertion(+) (limited to 'MAINTAINERS') diff --git a/MAINTAINERS b/MAINTAINERS index 783569e3c4b4..5d7bb3024e13 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2906,6 +2906,7 @@ F: drivers/video/backlight/ F: include/linux/backlight.h F: include/linux/pwm_backlight.h F: Documentation/devicetree/bindings/leds/backlight +F: Documentation/ABI/stable/sysfs-class-backlight BATMAN ADVANCED M: Marek Lindner -- cgit v1.2.3 From d55c028f8b25bdaaba9ae08026052b5b44d031b0 Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Tue, 9 Jul 2019 12:00:05 -0700 Subject: backlight: Expose brightness curve type through sysfs 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 88ba95bedb79 "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 Reviewed-by: Daniel Thompson Signed-off-by: Lee Jones --- MAINTAINERS | 1 + 1 file changed, 1 insertion(+) (limited to 'MAINTAINERS') diff --git a/MAINTAINERS b/MAINTAINERS index 5d7bb3024e13..fe75bb96a317 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2907,6 +2907,7 @@ F: include/linux/backlight.h F: include/linux/pwm_backlight.h F: Documentation/devicetree/bindings/leds/backlight F: Documentation/ABI/stable/sysfs-class-backlight +F: Documentation/ABI/testing/sysfs-class-backlight BATMAN ADVANCED M: Marek Lindner -- cgit v1.2.3