Re: [PATCH v3 00/11] backlight, lcd, led: Remove fbdev dependencies

On Thu, Mar 13, 2025 at 04:51:51PM +0000, Lee Jones wrote:

On Thu, 06 Mar 2025, Thomas Zimmermann wrote:

quoted

This series removes the remaining dependencies on fbdev from the
backlight, lcd and led subsystems. Each depends on fbdev events to
track display state. Make fbdev inform each subsystem via a dedicated
interface instead.

Patches 1 to 3 make fbdev track blank state for each display, so that
backlight code doesn't have to.

Patches 4 to 6 remove fbdev event handling from backlight code. Patches
7 and 8 remove fbdev event handling from lcd code and patches 9 and 10
do the same for led's backlight trigger.

The final patch removes the event constants from fbdev.

With the series applied, the three subsystems do no longer depend on
fbdev. It's also a clean up for fbdev. Fbdev used to send out a large
number of events. That mechanism has been deprecated for some time and
converted call to dedicated functions instead.

Testing is very welcome, as I don't have the hardware to test this
series.

v3:
- export several symbols
- static-inline declare empty placeholders
v2:
- avoid IS_REACHABLE() in source file (Lee)
- simplify several interfaces and helpers
- use lock guards
- initialize global lists and mutices

Thomas Zimmermann (11):
  fbdev: Rework fb_blank()
  fbdev: Track display blanking state
  fbdev: Send old blank state in FB_EVENT_BLANK
  backlight: Implement fbdev tracking with blank state from event
  backlight: Move blank-state handling into helper
  backlight: Replace fb events with a dedicated function call
  backlight: lcd: Move event handling into helpers
  backlight: lcd: Replace fb events with a dedicated function call
  leds: backlight trigger: Move blank-state handling into helper
  leds: backlight trigger: Replace fb events with a dedicated function
    call
  fbdev: Remove constants of unused events

 drivers/leds/trigger/ledtrig-backlight.c |  48 +++++-----
 drivers/video/backlight/backlight.c      |  93 +++++--------------
 drivers/video/backlight/lcd.c            | 108 +++++++++--------------
 drivers/video/fbdev/core/fb_backlight.c  |  12 +++
 drivers/video/fbdev/core/fb_info.c       |   1 +
 drivers/video/fbdev/core/fbmem.c         |  82 ++++++++++++++---
 drivers/video/fbdev/core/fbsysfs.c       |   8 +-
 include/linux/backlight.h                |  22 ++---
 include/linux/fb.h                       |  12 +--
 include/linux/lcd.h                      |  21 ++++-
 include/linux/leds.h                     |   6 ++
 11 files changed, 205 insertions(+), 208 deletions(-)

No immediately obvious issues from the LEDs side.

Still needs reviews from Backlight and fbdev.

I looked throught the series and it's a small step, but I think it's the
right direction for where we want backlight/fbdev/drm-kms to head towards
long-term. So on the series:

Acked-by: Simona Vetter <redacted>

Cheers, Sima

-- 
Lee Jones [李琼斯]

-- 
Simona Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch