linux-kernel - Re: [PATCH v2] media: ir-rx51: Switch to atomic PWM API

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Date:   Thu, 4 Nov 2021 18:43:25 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Maíra Canal <maira.canal@....br>
Cc:     sean@...s.org, mchehab@...nel.org, thierry.reding@...il.com,
        lee.jones@...aro.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: [PATCH v2] media: ir-rx51: Switch to atomic PWM API

On Thu, Nov 04, 2021 at 04:29:13PM +0100, Uwe Kleine-König wrote:
> On Sun, Oct 31, 2021 at 07:15:45PM -0300, Maíra Canal wrote:
> > Remove legacy PWM interface (pwm_config, pwm_enable, pwm_disable) and
> > replace it for the atomic PWM API.
> > 
> > Signed-off-by: Maíra Canal <maira.canal@....br>
> > ---
> > V1 -> V2: remove conceptually wrong chunk of code and correct the position
> > of pwm_init_state function
> > ---
> >  drivers/media/rc/ir-rx51.c | 16 +++++++++-------
> >  1 file changed, 9 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/media/rc/ir-rx51.c b/drivers/media/rc/ir-rx51.c
> > index a0d9c02a7588..41d4a4338072 100644
> > --- a/drivers/media/rc/ir-rx51.c
> > +++ b/drivers/media/rc/ir-rx51.c
> > @@ -19,6 +19,7 @@
> >  struct ir_rx51 {
> >  	struct rc_dev *rcdev;
> >  	struct pwm_device *pwm;
> > +	struct pwm_state *state;
> >  	struct hrtimer timer;
> >  	struct device	     *dev;
> >  	wait_queue_head_t     wqueue;
> > @@ -32,22 +33,22 @@ struct ir_rx51 {
> >  
> >  static inline void ir_rx51_on(struct ir_rx51 *ir_rx51)
> >  {
> > -	pwm_enable(ir_rx51->pwm);
> > +	ir_rx51->state->enabled = true;
> > +	pwm_apply_state(ir_rx51->pwm, ir_rx51->state);
> >  }
> >  
> >  static inline void ir_rx51_off(struct ir_rx51 *ir_rx51)
> >  {
> > -	pwm_disable(ir_rx51->pwm);
> > +	ir_rx51->state->enabled = false;
> > +	pwm_apply_state(ir_rx51->pwm, ir_rx51->state);
> >  }
> >  
> >  static int init_timing_params(struct ir_rx51 *ir_rx51)
> >  {
> > -	struct pwm_device *pwm = ir_rx51->pwm;
> > -	int duty, period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, ir_rx51->freq);
> > +	struct pwm_state *state = ir_rx51->state;
> >  
> > -	duty = DIV_ROUND_CLOSEST(ir_rx51->duty_cycle * period, 100);
> > -
> > -	pwm_config(pwm, duty, period);
> > +	state->period = DIV_ROUND_CLOSEST(NSEC_PER_SEC, ir_rx51->freq);
> > +	pwm_set_relative_duty_cycle(state, ir_rx51->duty_cycle, 100);
> >  
> >  	return 0;
> >  }
> > @@ -242,6 +243,7 @@ static int ir_rx51_probe(struct platform_device *dev)
> >  
> >  	/* Use default, in case userspace does not set the carrier */
> >  	ir_rx51.freq = DIV_ROUND_CLOSEST_ULL(pwm_get_period(pwm), NSEC_PER_SEC);
> > +	pwm_init_state(pwm, ir_rx51.state);
> >  	pwm_put(pwm);
> >  
> 
> Orthogonal to this patch I wonder why probe calls pwm_get() and
> pwm_put(), just to have another call to pwm_get() in the open callback.
> 
> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>

Oh, I missed something: the member added to struct ir_rx51 must be a
plain struct pwm_state, not a pointer to it. As suggested here the
driver runs into a NULL pointer exception.

Best regards
Uwe


-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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