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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 <mka@chromium.org> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> Signed-off-by: Lee Jones <lee.jones@linaro.org>
2019-07-10 03:00:05 +08:00
What: /sys/class/backlight/<backlight>/scale
Date: July 2019
KernelVersion: 5.4
Contact: Daniel Thompson <daniel.thompson@linaro.org>
Description:
Description of the scale of the brightness curve.
The human eye senses brightness approximately logarithmically,
hence linear changes in brightness are perceived as being
non-linear. To achieve a linear perception of brightness changes
controls like sliders need to apply a logarithmic mapping for
backlights with a linear brightness curve.
Possible values of the attribute are:
unknown
The scale of the brightness curve is unknown.
linear
The brightness changes linearly with each step. Brightness
controls should apply a logarithmic mapping for a linear
perception.
non-linear
The brightness changes non-linearly with each step. Brightness
controls should use a linear mapping for a linear perception.
docs: ABI: sysfs-class-backlight: unify ABI documentation 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>
2020-10-30 15:40:56 +08:00
What: /sys/class/backlight/<backlight>/ambient_light_level
Date: Apr, 2010
KernelVersion: v2.6.35
Contact: Michael Hennerich <michael.hennerich@analog.com>
Description:
(RO) Get conversion value of the light sensor.
The value is automatically updated every 80 ms when the
light sensor is enabled.
The value range is device-driver specific:
For ADP8870:
It returns integer between 0 (dark) and 8000 (max ambient
brightness).
For ADP8860:
It returns a 13-bits integer.
What: /sys/class/backlight/<backlight>/ambient_light_zone
Date: Apr, 2010
KernelVersion: v2.6.35
Contact: Michael Hennerich <michael.hennerich@analog.com>,
device-drivers-devel@blackfin.uclinux.org
Description:
(RW) Read or write the specific brightness level at which the
backlight operates.
The value meaning is device-driver specific:
For ADP8860:
== ==========================
0 Off: Backlight set to 0 mA
1 Level 1: daylight
2 Level 2: bright
3 Level 3: dark
== ==========================
For ADP8870:
== ==========================
0 Off: Backlight set to 0 mA
1 Level 1: daylight
2 Level 2: bright
3 Level 3: office
4 Level 4: indoor
5 Level 5: dark
== ==========================
Writing 0 returns to normal/automatic ambient light level
operation.
It can be enabled by writing the value stored in
/sys/class/backlight/<backlight>/max_brightness to
/sys/class/backlight/<backlight>/brightness.
docs: ABI: sysfs-class-backlight: unify ambient light zone nodes ./scripts/get_abi.pl is warning about duplicated symbol definition: Warning: /sys/class/backlight/<backlight>/l1_daylight_max is defined 2 times: ./Documentation/ABI/testing/sysfs-class-backlight-driver-adp8870:4 ./Documentation/ABI/testing/sysfs-class-backlight-adp8860:12 What happens is that 3 drivers use the same pattern to report max and dim setting for different ambient light zones. It should be noticed that the adp8870 doc was missing an entry for l1_daylight_dim, which was fixed on this patch. While the ambient light zone is device-specific, the sysfs definition is actually common. So, unify them at: Documentation/ABI/testing/sysfs-class-backlight and use as the contact point, the e-mail reported by get_maintainers.pl for the subsystem. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/c13c6ebd03cd04a0d15d89018f8d529918fc0a73.1621413933.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2021-05-19 16:51:45 +08:00
What: /sys/class/backlight/<backlight>/<ambient light zone>_max
Date: Sep, 2009
KernelVersion: v2.6.32
Contact: device-drivers-devel@blackfin.uclinux.org
Description:
Control the maximum brightness for <ambient light zone>
on this <backlight>. Values are between 0 and 127. This file
will also show the brightness level stored for this
<ambient light zone>.
The <ambient light zone> is device-driver specific:
For ADP5520 and ADP5501, <ambient light zone> can be:
=========== ================================================
Ambient sysfs entry
light zone
=========== ================================================
daylight /sys/class/backlight/<backlight>/daylight_max
office /sys/class/backlight/<backlight>/office_max
dark /sys/class/backlight/<backlight>/dark_max
=========== ================================================
For ADP8860, <ambient light zone> can be:
=========== ================================================
Ambient sysfs entry
light zone
=========== ================================================
l1_daylight /sys/class/backlight/<backlight>/l1_daylight_max
l2_office /sys/class/backlight/<backlight>/l2_office_max
l3_dark /sys/class/backlight/<backlight>/l3_dark_max
=========== ================================================
For ADP8870, <ambient light zone> can be:
=========== ================================================
Ambient sysfs entry
light zone
=========== ================================================
l1_daylight /sys/class/backlight/<backlight>/l1_daylight_max
l2_bright /sys/class/backlight/<backlight>/l2_bright_max
l3_office /sys/class/backlight/<backlight>/l3_office_max
l4_indoor /sys/class/backlight/<backlight>/l4_indoor_max
l5_dark /sys/class/backlight/<backlight>/l5_dark_max
=========== ================================================
See also: /sys/class/backlight/<backlight>/ambient_light_zone.
What: /sys/class/backlight/<backlight>/<ambient light zone>_dim
Date: Sep, 2009
KernelVersion: v2.6.32
Contact: device-drivers-devel@blackfin.uclinux.org
Description:
Control the dim brightness for <ambient light zone>
on this <backlight>. Values are between 0 and 127, typically
set to 0. Full off when the backlight is disabled.
This file will also show the dim brightness level stored for
this <ambient light zone>.
The <ambient light zone> is device-driver specific:
For ADP5520 and ADP5501, <ambient light zone> can be:
=========== ================================================
Ambient sysfs entry
light zone
=========== ================================================
daylight /sys/class/backlight/<backlight>/daylight_dim
office /sys/class/backlight/<backlight>/office_dim
dark /sys/class/backlight/<backlight>/dark_dim
=========== ================================================
For ADP8860, <ambient light zone> can be:
=========== ================================================
Ambient sysfs entry
light zone
=========== ================================================
l1_daylight /sys/class/backlight/<backlight>/l1_daylight_dim
l2_office /sys/class/backlight/<backlight>/l2_office_dim
l3_dark /sys/class/backlight/<backlight>/l3_dark_dim
=========== ================================================
For ADP8870, <ambient light zone> can be:
=========== ================================================
Ambient sysfs entry
light zone
=========== ================================================
l1_daylight /sys/class/backlight/<backlight>/l1_daylight_dim
l2_bright /sys/class/backlight/<backlight>/l2_bright_dim
l3_office /sys/class/backlight/<backlight>/l3_office_dim
l4_indoor /sys/class/backlight/<backlight>/l4_indoor_dim
l5_dark /sys/class/backlight/<backlight>/l5_dark_dim
=========== ================================================
See also: /sys/class/backlight/<backlight>/ambient_light_zone.