[U-Boot] [PATCH] video: backlight: fix pwm invertation

[Stefan Mavrodiev]

Hi,

On 7/2/19 11:42 AM, Nicolas Chauvet wrote:
> Le mar. 2 juil. 2019 à 09:41, Stefan Mavrodiev <stefan at olimex.com> a écrit :
>> Hi,
>>
>> On 6/27/19 9:56 PM, marvin24 at posteo.de wrote:
>>> Am Freitag, 21. Juni 2019, 22:01:35 CEST schrieb Marc Dietrich:
>>>> Fixes: 57e7775413 ("video: backlight: Parse PWM polarity cell")
>>>>
>>>> set_pwm will always fail if pwm_set_invert is not implemented, leaving the
>>>> backlight dark. Fix this by calling pwm_set_invert only if pwm is inverted.
>> I'm not sure if this is true. pwm_set_invert() checks for .set_invert.
>> Which pwm driver you're using?
> This is drivers/pwm/pwm_tegra.c
> Here .set_invert is not implemented.
>
> Thx for the review.
>
You're right. Some drivers has #pwm-cells = <2> and in this case 
polarity is 0.

However your approach is wrong. You will break other drivers with 
#pwm-cells = <3>.
I think your patch should look something like this:

ret = pwm_set_invert(priv->pwm, priv->channel, priv->polarity);
if (ret == -ENOSYS)
     ret = 0;

return log_ret(ret);

This will not return error if set_inverted is not implemented.


Stefan