Re: [PATCH v6 4/4] media: pwm-ir-tx: trigger edges from hrtimer interrupt context

Sean Young
2023-12-09T09:52:14Z

On Fri, Dec 08, 2023 at 05:29:55PM +0100, Thierry Reding wrote:
> On Wed, Nov 29, 2023 at 09:13:37AM +0000, Sean Young wrote:
> > This makes the generated IR much more precise. Before this change, the
> > driver is unreliable and many users opted to use gpio-ir-tx instead.
> >
> > Signed-off-by: Sean Young <sean@mess.org>
> > ---
> > drivers/media/rc/pwm-ir-tx.c | 79 ++++++++++++++++++++++++++++++++++--
> > 1 file changed, 76 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/media/rc/pwm-ir-tx.c b/drivers/media/rc/pwm-ir-tx.c
> > index cf51e2760975..8575c4596d7b 100644
> > --- a/drivers/media/rc/pwm-ir-tx.c
> > +++ b/drivers/media/rc/pwm-ir-tx.c
> > @@ -10,6 +10,8 @@
> > #include <linux/slab.h>
> > #include <linux/of.h>
> > #include <linux/platform_device.h>
> > +#include <linux/hrtimer.h>
> > +#include <linux/completion.h>
> > #include <media/rc-core.h>
> >
> > #define DRIVER_NAME "pwm-ir-tx"
> > @@ -17,8 +19,14 @@
> >
> > struct pwm_ir {
> > struct pwm_device *pwm;
> > - unsigned int carrier;
> > - unsigned int duty_cycle;
> > + struct hrtimer timer;
> > + struct completion tx_done;
> > + struct pwm_state *state;
> > + u32 carrier;
> > + u32 duty_cycle;
> > + uint *txbuf;
>
> Maybe mark this as const to signal that it's not going to get modified?

Ah nice, I usually forget const.

> > + uint txbuf_len;
> > + uint txbuf_index;
>
> uint is rather rare. Or so I thought. There seem to be quite a few
> occurrences throughout the kernel. I'd still prefer unsigned int over
> this abbreviated form, but ultimately up to you and Mauro to decide.

Yes, unsigned int is used a lot more. Changed.

> > static int pwm_ir_probe(struct platform_device *pdev)
> > {
> > struct pwm_ir *pwm_ir;
> > @@ -103,10 +167,19 @@ static int pwm_ir_probe(struct platform_device *pdev)
> > if (!rcdev)
> > return -ENOMEM;
> >
> > + if (pwm_is_atomic(pwm_ir->pwm)) {
> > + init_completion(&pwm_ir->tx_done);
> > + hrtimer_init(&pwm_ir->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> > + pwm_ir->timer.function = pwm_ir_timer;
> > + rcdev->tx_ir = pwm_ir_tx_atomic;
> > + } else {
> > + dev_info(&pdev->dev, "tx will not be accurate as pwm device does not support atomic mode");
>
> s/tx/TX and s/pwm/PWM/? Also, I'm a bit unhappy about "atomic mode" here
> because the term is overloaded in PWM. If you call pwm_appy_*() then by
> definition it's going to be "atomic" in the "atomic state" sense. So
> maybe switch to something like:
>
> "TX will not be accurate as PWM device might sleep"
>
> ?

Very nice, changed.

Thanks
Sean