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

[Daniel Thompson]

On Fri, Jul 09, 2021 at 03:53:16PM +0200, Noralf Trønnes wrote:
> 
> 
> Den 09.07.2021 15.26, skrev Marek Vasut:
> > 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: <stable at vger.kernel.org> # 5.4+
Cc: <stable at vger.kernel.org> # 4.19.x: ec665b756e6f7: backlight: gpio-backlight: Correct initial power state handling


> > Signed-off-by: Marek Vasut <marex at denx.de>
> > Cc: Daniel Thompson <daniel.thompson at linaro.org>
> > Cc: Meghana Madhyastha <meghana.madhyastha at gmail.com>
> > Cc: Noralf Trønnes <noralf at tronnes.org>
> > Cc: Sean Paul <seanpaul at chromium.org>
> > Cc: Thierry Reding <treding at nvidia.com>
> > ---
> 
> Acked-by: Noralf Trønnes <noralf at tronnes.org>

With the above (or something similar to avoid problems with v4.19):
Reviewed-by: Daniel Thompson <daniel.thompson at linaro.org>


Daniel.