# Re: \[PATCH\] backlight: pwm\_bl: Fix brightness levels for non-DT case.

- List: linux-fbdev
- 2 messages, 2 authors
- Page: https://ratatoskr.run/linux-fbdev/2018/08/5363903/t

## Re: \[PATCH\] backlight: pwm\_bl: Fix brightness levels for non-DT case.

- From: Robert Jarzmik \<robert.jarzmik@free.fr\>
- Date: 2018-08-25 08:04:22 
- Message: https://ratatoskr.run/linux-fbdev/2018/08/5363903.md

```text
Enric Balletbo i Serra [ref] writes:

> Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED
> linearly to human eye")' allows the possibility to compute a default
> brightness table when there isn't the brightness-levels property in the
> DT. Unfortunately the changes made broke the pwm backlight for the
> non-DT boards.
>
> Usually, the non-DT boards don't pass the brightness levels via platform
> data, instead, they set the max_brightness in their platform data and the
> driver calculates the level without a table. The ofending patch assumed
> that when there is no brightness levels table we should create one, but this
> is clearly wrong for the non-DT case.
>
> After this patch the code handles the DT and the non-DT case taking in
> consideration also if max_brightness is set or not. The default table is
> only created when neither, brightness-levels and max_brightness, are
> set.
>
> The patch also fixes another issue found by Robert. Before this patch
> looks like a division by 0 was possible when state.period returned 0 by
> pwm_get_state(). This is because pwm_get_state() was called before
> pwm_apply_args() so state.period was not initialized. The patch moves
> the pwm_apply_args() call before any call to pwm_get_state().
>
> Fixes: '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")'
> Reported-by: Robert Jarzmik <robert.jarzmik@free.fr>
> Signed-off-by: Enric Balletbo i Serra <redacted>
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>

Cheers.

--
Robert
```

## Re: Re: \[PATCH\] backlight: pwm\_bl: Fix brightness levels for non-DT case.

- From: Daniel Thompson \<hidden\>
- Date: 2018-09-20 16:23:54 
- Message: https://ratatoskr.run/linux-fbdev/2018/09/5386363.md

```text
On 25/08/18 01:04, Robert Jarzmik wrote:
> Enric Balletbo i Serra [ref] writes:
> 
>> Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED
>> linearly to human eye")' allows the possibility to compute a default
>> brightness table when there isn't the brightness-levels property in the
>> DT. Unfortunately the changes made broke the pwm backlight for the
>> non-DT boards.
>>
>> Usually, the non-DT boards don't pass the brightness levels via platform
>> data, instead, they set the max_brightness in their platform data and the
>> driver calculates the level without a table. The ofending patch assumed
>> that when there is no brightness levels table we should create one, but this
>> is clearly wrong for the non-DT case.
>>
>> After this patch the code handles the DT and the non-DT case taking in
>> consideration also if max_brightness is set or not. The default table is
>> only created when neither, brightness-levels and max_brightness, are
>> set.
>>
>> The patch also fixes another issue found by Robert. Before this patch
>> looks like a division by 0 was possible when state.period returned 0 by
>> pwm_get_state(). This is because pwm_get_state() was called before
>> pwm_apply_args() so state.period was not initialized. The patch moves
>> the pwm_apply_args() call before any call to pwm_get_state().
>>
>> Fixes: '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")'
>> Reported-by: Robert Jarzmik <robert.jarzmik@free.fr>
>> Signed-off-by: Enric Balletbo i Serra <redacted>
> Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>

Acked-by: Daniel Thompson <redacted>

(and sorry for the delay)


Daniel.
```