Add a generic driver for LED-based backlight

Submitted by Jean-Jacques Hiblot on July 1, 2019, 3:14 p.m.

Details

Reviewer None
Submitted July 1, 2019, 3:14 p.m.
Last Updated Sept. 10, 2019, 1:27 p.m.
Revision 5

Cover Letter(s)

Revision 1
      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.

This series takes it from there and implements the binding that was
discussed in https://patchwork.kernel.org/patch/7293991/. In this new
binding the backlight device is a child of the LED controller instead of
being another platform device that uses a phandle to reference a LED.

Jean-Jacques Hiblot (2):
  leds: of: create a child device if the LED node contains a
    "compatible" string
  devicetree: Update led binding

Tomi Valkeinen (2):
  backlight: add led-backlight driver
  devicetree: Add led-backlight binding

 .../devicetree/bindings/leds/common.txt       |   3 +
 .../video/backlight/led-backlight.txt         |  39 ++++
 drivers/leds/led-class.c                      |  16 ++
 drivers/video/backlight/Kconfig               |   7 +
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/led_bl.c              | 217 ++++++++++++++++++
 include/linux/leds.h                          |  11 +
 7 files changed, 294 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/video/backlight/led-backlight.txt
 create mode 100644 drivers/video/backlight/led_bl.c
    
Revision 2
      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.

The series affects the LED core and add a new backlight driver.

changes in v2:
- bkl: the backlight can use more than one LED. As a consequence don't make
  the backlight device a child of a LED controller.
- bkl: make brightness-levels and default-brightness-level optional
- bkl: removed the option to use a GPIO enable.
- bkl: removed the option to use a regulator. It should be handled by the
  LED core
- led: removed the mechanism to bind a child device for each LED
- led: improve the way of_get_led() works and add a managed version of it

Jean-Jacques Hiblot (2):
  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 |  29 +++
 drivers/leds/led-class.c                      |  92 +++++++
 drivers/video/backlight/Kconfig               |   7 +
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/led_bl.c              | 235 ++++++++++++++++++
 include/linux/leds.h                          |   6 +
 6 files changed, 370 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
 create mode 100644 drivers/video/backlight/led_bl.c
    
Revision 3
      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 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 optionnal
- 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 (2):
  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                      |  92 ++++++
 drivers/video/backlight/Kconfig               |   7 +
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/led_bl.c              | 268 ++++++++++++++++++
 include/linux/leds.h                          |   6 +
 6 files changed, 402 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
 create mode 100644 drivers/video/backlight/led_bl.c
    
Revision 4
      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 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 (2):
  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                      |  92 ++++++
 drivers/video/backlight/Kconfig               |   7 +
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/led_bl.c              | 268 ++++++++++++++++++
 include/linux/leds.h                          |   6 +
 6 files changed, 402 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
 create mode 100644 drivers/video/backlight/led_bl.c
    
Revision 5
      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 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 (2):
  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                      |  92 +++++++
 drivers/video/backlight/Kconfig               |   7 +
 drivers/video/backlight/Makefile              |   1 +
 drivers/video/backlight/led_bl.c              | 260 ++++++++++++++++++
 include/linux/leds.h                          |   6 +
 6 files changed, 394 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/backlight/led-backlight.txt
 create mode 100644 drivers/video/backlight/led_bl.c
    

Revisions