[PATCH v9 0/5] Add a generic driver for LED-based backlight

[Jean-Jacques Hiblot]

This series aims to add a led-backlight driver, similar to pwm-backlight,
but using a LED class device underneath.

A few years ago (2015), Tomi Valkeinen posted a series implementing a
backlight driver on top of a LED device:
https://patchwork.kernel.org/patch/7293991/
https://patchwork.kernel.org/patch/7294001/
https://patchwork.kernel.org/patch/7293981/

The discussion stopped because Tomi lacked the time to work on it.

changes in v9:
- let to_of_node() check if the fwnode is actually a of_node
- add some checks in of_led_get()
- let dev_of_node() do the check about OF availabilty
- refactor led_bl_probe() to register a cleanup function with
  devm_add_action_or_reset(). This simplifies the error handling (which
  was not 100% done in v7) and allows to get rid of led_bl_remove()

changes in v8:
- use class_find_device_by_of_node() instead of class_find_device()
- renamed devm_led_get() as devm_of_led_get()

changes in v7:
- rebased on top of linux-leds/for-next
- populate the of_node member of the LED device if fwnode is a of_node
  (this is a new patch and the first of the series).
- devm_led_get() works only when the device tree is used. Add a few checks
  for that.  

changes in v6:
- trim the list of included headers
- remove useless definition of BKL_FULL_BRIGHTNESS

changes in v5:
- removed LED brightness scaling
- disable sysfs the interface of the LEDs when used by the backlight device

changes in v4:
- fix dev_err() messages and commit logs following the advices of Pavel
- cosmetic changes (indents, getting rid of  "? 1 : 0" in
  led_match_led_node())

changes in v3:
- dt binding: don't limit the brightness range to 0-255. Use the range of
  the underlying LEDs. as a side-effect, all LEDs must now have the same
  range
- driver: Adapt to dt binding update.
- driver: rework probe() for clarity and remove the remaining goto.

changes in v2:
- handle more than one LED.
- don't make the backlight device a child of the LED controller.
- make brightness-levels and default-brightness-level optional
- removed the option to use a GPIO enable.
- removed the option to use a regulator. It should be handled by the LED
  core
- don't make any change to the LED core (not needed anymore)

Jean-Jacques Hiblot (3):
  leds: populate the device's of_node
  leds: Add managed API to get a LED from a device driver
  dt-bindings: backlight: Add led-backlight binding

Tomi Valkeinen (2):
  leds: Add of_led_get() and led_put()
  backlight: add led-backlight driver

 .../bindings/leds/backlight/led-backlight.txt |  28 ++
 drivers/leds/led-class.c                      | 103 ++++++-
 drivers/video/backlight/Kconfig               |   7 +
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/led_bl.c              | 258 ++++++++++++++++++
 include/linux/leds.h                          |   6 +
 6 files changed, 402 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
 create mode 100644 drivers/video/backlight/led_bl.c

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2.17.1