Re: [PATCH 2/2] backlight: pwm_bl: Get number of brightness levels for CIE 1931 from the device tree

[Pavel Machek]

On Mon 2019-06-10 16:37:39, Matthias Kaehlcke wrote:
> Commit 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED
> linearly to human eye") uses pwm_period / hweight32(pwm_period) as
> as heuristic to determine the number of brightness levels when the DT
> doesn't provide a brightness level table. This heuristic is broken
> and can result in excessively large brightness tables.
> 
> Instead of using the heuristic try to retrieve the number of
> brightness levels from the device tree (property 'max-brightness'
> + 1). If the value is not specified use a default of 256 levels.
> 
> Fixes: 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")

I don't think this one is suitable for stable. I'm pretty sure the
heuristics works well for many boards, and you just replaced it with
another heuristics ("256").

> Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>

Acked-by: Pavel Machek <pavel@xxxxxx>

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