Re: [PATCH v12 2/2] leds: Add driver for Qualcomm LPG

[Doug Anderson]

Hi,

On Tue, Feb 15, 2022 at 8:54 PM Bjorn Andersson
<bjorn.andersson@xxxxxxxxxx> wrote:
>
> +static int lpg_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +                        const struct pwm_state *state)
> +{
> +       struct lpg *lpg = container_of(chip, struct lpg, pwm);
> +       struct lpg_channel *chan = &lpg->channels[pwm->hwpwm];
> +       int ret;
> +
> +       if (state->polarity != PWM_POLARITY_NORMAL)
> +               return -EINVAL;
> +
> +       mutex_lock(&lpg->lock);
> +
> +       if (state->enabled) {
> +               ret = lpg_calc_freq(chan, state->period);
> +               if (ret < 0)
> +                       goto out_unlock;
> +
> +               lpg_calc_duty(chan, state->duty_cycle);
> +       }
> +       chan->enabled = state->enabled;
> +
> +       lpg_apply(chan);
> +
> +       triled_set(lpg, chan->triled_mask, chan->enabled ? chan->triled_mask : 0);
> +
> +out_unlock:
> +       mutex_unlock(&lpg->lock);
> +
> +       return ret;
> +}

My compiler (correctly) yelled that `ret` is returned uninitialized if
`state->enabled` is false. I initialized `ret` to 0 and the problem
went away. I assume that the patch will need to spin to fix that
unless everything else looks great and a maintainer wants to fix that
when applying.

With that fix, I was able to use Bjorn's patch along with Satya's
patches adding pm8350c support (removing the now defunct
"pwm_9bit_mask" property) to make the PWM on my board work. Thus, once
the error my compiler complained about is fixed I'm happy with my
`Tested-by` being added.

For now I haven't actually reviewed the code here, but if folks feel
like it needs an extra pair of eyes then please yell and I'll find
some time to do it.

-Doug