linux.git/drivers/video/backlight/backlight.c, branch v5.8

backlight: Add backlight_device_get_by_name()

2020-05-11T06:39:16+00:00

Add a way to lookup a backlight device based on its name.
Will be used by a USB display gadget getting the name from configfs.

Signed-off-by: Noralf Trønnes 
Reviewed-by: Sam Ravnborg 
Reviewed-by: Daniel Thompson 
Acked-by: Jingoo Han 
Signed-off-by: Lee Jones

backlight: Expose brightness curve type through sysfs

2019-09-02T14:55:03+00:00

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

Revert "backlight/fbcon: Add FB_EVENT_CONBLANK"

2019-06-12T18:29:40+00:00

This reverts commit 994efacdf9a087b52f71e620b58dfa526b0cf928.

The justification is that if hw blanking fails (i.e. fbops->fb_blank)
fails, then we still want to shut down the backlight. Which is exactly
_not_ what fb_blank() does and so rather inconsistent if we end up
with different behaviour between fbcon and direct fbdev usage. Given
that the entire notifier maze is getting in the way anyway I figured
it's simplest to revert this not well justified commit.

v2: Add static inline to the dummy version.

Cc: Richard Purdie 
Signed-off-by: Daniel Vetter 
Reviewed-by: Sam Ravnborg 
Reviewed-by: Maarten Lankhorst 
Acked-by: Daniel Thompson 
Cc: Lee Jones 
Cc: Daniel Thompson 
Cc: Jingoo Han 
Cc: Bartlomiej Zolnierkiewicz 
Cc: Daniel Vetter 
Cc: Hans de Goede 
Cc: Yisheng Xie 
Cc: linux-fbdev@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20190528090304.9388-25-daniel.vetter@ffwll.ch

treewide: Add SPDX license identifier for more missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have MODULE_LICENCE("GPL*") inside which was used in the initial
   scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

video: backlight: Add devres versions of of_find_backlight

2018-01-29T15:34:53+00:00

Add devm_of_find_backlight and the corresponding release
function because some drivers use devres versions of functions
for acquiring device resources.

Acked-by: Daniel Thompson 
Reviewed-by: Noralf Trønnes 
Reviewed-by: Sean Paul 
Signed-off-by: Meghana Madhyastha 
Signed-off-by: Sean Paul 
Link: https://patchwork.freedesktop.org/patch/msgid/021f8fecfa3f374dc5dcb70fb07a6f6b019bea7b.1516810725.git.meghana.madhyastha@gmail.com

video: backlight: Add of_find_backlight helper in backlight.c

2018-01-29T15:34:53+00:00

Add of_find_backlight, a helper function which is a generic version
of tinydrm_of_find_backlight that can be used by other drivers to avoid
repetition of code and simplify things.

Acked-by: Daniel Thompson 
Reviewed-by: Noralf Trønnes 
Reviewed-by: Sean Paul 
Reviewed-by: Thierry Reding 
Signed-off-by: Meghana Madhyastha 
Signed-off-by: Sean Paul 
Link: https://patchwork.freedesktop.org/patch/msgid/116d160ba78be2e6dcbdcb6855622bce67da9472.1516810725.git.meghana.madhyastha@gmail.com

backlight: Report error on failure

2017-05-30T08:27:53+00:00

It is possible to update the backlight power and the brightness using
the sysfs and on writing it either returns the count or if the callback
function does not exist then returns the error code 'ENXIO'.

We have a situation where the userspace client is writing to the sysfs
to update the power and since the callback function exists the client
receives the return value as count and considers the operation to be
successful. That is correct as the write to the sysfs was successful.
But there is no way to know if the actual operation was done or not.

backlight_update_status() returns the error code if it fails. Pass that
to the userspace client who is trying to update the power so that the
client knows that the operation failed.

Signed-off-by: Sudip Mukherjee 
Acked-by: Daniel Thompson 
Signed-off-by: Lee Jones

video / backlight: remove the backlight_device_registered API

2016-05-04T21:41:14+00:00

Since we will need the backlight_device_get_by_type API, we can use it
instead of the backlight_device_registered API whenever necessary so
remove the backlight_device_registered API.

Signed-off-by: Aaron Lu 
Acked-by: Jingoo Han 
Signed-off-by: Rafael J. Wysocki

video / backlight: add two APIs for drivers to use

2016-05-04T21:41:14+00:00

It is useful to get the backlight device's pointer and use it to set
backlight in some cases(the following patch will make use of it) so add
the two APIs and export them.

Signed-off-by: Aaron Lu 
Acked-by: Jingoo Han 
Signed-off-by: Rafael J. Wysocki

backlight: Show brightness even if get_brightness is not implemented

2014-06-23T12:26:02+00:00

Many implementations of get_brightness operation returns only value
of props.brightness field. This change makes such implementations
unnecessary.

Acked-by: Jingoo Han 
Signed-off-by: Andrzej Hajda 
Signed-off-by: Lee Jones