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2020-10-30docs: ABI: sysfs-class-backlight: unify ABI documentationMauro Carvalho Chehab1-0/+60
Both adp8860 and adp8870 define some extensions to the backlight class. This causes warnings: Warning: /sys/class/backlight/<backlight>/ambient_light_level is defined 2 times: /sys/class/backlight/<backlight>/ambient_light_level:8 /sys/class/backlight/<backlight>/ambient_light_level:30 Warning: /sys/class/backlight/<backlight>/ambient_light_zone is defined 2 times: /sys/class/backlight/<backlight>/ambient_light_zone:18 /sys/class/backlight/<backlight>/ambient_light_zone:40 As ABI definitions shouldn't be duplicated. Unfortunately, the ABI is dependent on the specific device features. As such, ambient_light_level range is somewhat different among the supported devices. The ambient_light_zone is even worse: the meanings of each preset are different, and there's no ABI to retrieve the supported types nor their meanins. Unfortunately, it is too late to fix it without causing regressions, as this has been used since Kernel v2.6.35. Rewrite those ABI documentation using the current documentation as a reference, and double-checking at the datasheets: https://www.analog.com/media/en/technical-documentation/data-sheets/ADP8870.pdf https://www.analog.com/media/en/technical-documentation/data-sheets/ADP8860.pdf in order to properly document the differences between those two drivers. Acked-by: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/342195ad5a819d9bcfcebc133c77ab69b4211672.1604042072.git.mchehab+huawei@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-09-02backlight: Expose brightness curve type through sysfsMatthias Kaehlcke1-0/+26
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 <mka@chromium.org> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Lee Jones <lee.jones@linaro.org>