Re: [PATCH] video: backlight: Drop maximum brightness override for brightness zero

On Fri, Jul 09, 2021 at 03:53:16PM +0200, Noralf Trønnes wrote:

Den 09.07.2021 15.26, skrev Marek Vasut:

quoted

The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper
in backlight.c") says that gpio-backlight uses brightness as power state.
This has been fixed since in ec665b756e6f7 ("backlight: gpio-backlight:
Correct initial power state handling") and other backlight drivers do not
require this workaround. Drop the workaround.

This fixes the case where e.g. pwm-backlight can perfectly well be set to
brightness 0 on boot in DT, which without this patch leads to the display
brightness to be max instead of off.

Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c")

I not sure about the rules, but if this is automatically picked up for
stable, maybe this is needed to avoid changing behaviour on 4.19:


of_find_backlight() was added in 4.17 and the gpio fix in 5.4.

Or perhaps there are other ways to signal this dependency.

Agree we need to make sure the Fixes: tag doesn't provoke regressions
in v4.19.

Is this the syntax appropriate?

Cc: <redacted> # 5.4+
Cc: <redacted> # 4.19.x: ec665b756e6f7: backlight: gpio-backlight: Correct initial power state handling

quoted

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Daniel Thompson <redacted>
Cc: Meghana Madhyastha <redacted>
Cc: Noralf Trønnes <redacted>
Cc: Sean Paul <redacted>
Cc: Thierry Reding <redacted>
---

Acked-by: Noralf Trønnes <redacted>

With the above (or something similar to avoid problems with v4.19):
Reviewed-by: Daniel Thompson <redacted>


Daniel.