Re: [PATCH v2 1/3] iio: gyro: adxrs290: Add triggered buffer support

[Nishant Malpani]

Hello,

Thanks for the review, Andy.

...

On Thu, Sep 3, 2020 at 6:50 PM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
>
> On Thu, Sep 3, 2020 at 4:10 PM Nishant Malpani <nish.malpani25@xxxxxxxxx> wrote:
> >
> > Provide a way for continuous data capture by setting up buffer support. The
> > data ready signal exposed at the SYNC pin of the ADXRS290 is exploited as
> > a hardware interrupt which triggers to fill the buffer.
> >
> > Triggered buffer setup was tested with both hardware trigger (DATA_RDY) and
> > software triggers (sysfs-trig & hrtimer).
>
> ...
>
> > +static int adxrs290_set_mode(struct iio_dev *indio_dev, enum adxrs290_mode mode)
> > +{
> > +       struct adxrs290_state *st = iio_priv(indio_dev);
> > +       int val, ret;
> > +
> > +       if (st->mode == mode) {
>
> > +               ret = 0;
> > +               goto done;
>
> Unlocking the not locked mutex is not good. Have you followed the
> Submitting Patches Checklist? It in particular suggests few debug
> options, like LOCKDEP, to be enabled.
>

Yikes, silly me. Thanks for the suggestion. Will fix this in v3.

> > +       }
> > +
> > +       mutex_lock(&st->lock);
> > +
> > +       ret = spi_w8r8(st->spi, ADXRS290_READ_REG(ADXRS290_REG_POWER_CTL));
> > +       if (ret < 0)
> > +               goto done;
> > +
> > +       val = ret;
> > +
> > +       switch (mode) {
> > +       case ADXRS290_MODE_STANDBY:
> > +               val &= ~ADXRS290_MEASUREMENT;
> > +               break;
> > +       case ADXRS290_MODE_MEASUREMENT:
> > +               val |= ADXRS290_MEASUREMENT;
> > +               break;
> > +       default:
> > +               ret = -EINVAL;
> > +               goto done;
> > +       }
> > +
> > +       ret = adxrs290_spi_write_reg(st->spi,
> > +                                    ADXRS290_REG_POWER_CTL,
> > +                                    val);
> > +       if (ret < 0) {
> > +               dev_err(&st->spi->dev, "unable to set mode: %d\n", ret);
> > +               goto done;
> > +       }
> > +
> > +       /* update cached mode */
> > +       st->mode = mode;
> > +
>
> > +done:
>
> Much better to call it out_unlock. It will help eliminate the mistakes
> like above.
>

Yes, makes sense.

> > +       mutex_unlock(&st->lock);
> > +       return ret;
> > +}
>
> ...
>
>
> What about
>
>   ret = -EINVAL;
>
> >         switch (mask) {
> >         case IIO_CHAN_INFO_LOW_PASS_FILTER_3DB_FREQUENCY:
> >                 lpf_idx = adxrs290_find_match(adxrs290_lpf_3db_freq_hz_table,
> >                                               ARRAY_SIZE(adxrs290_lpf_3db_freq_hz_table),
> >                                               val, val2);
> > -               if (lpf_idx < 0)
> > -                       return -EINVAL;
>
> > +               if (lpf_idx < 0) {
>
> > +                       ret = -EINVAL;
> > +                       break;
> > +               }
>
> Simple
>   break;
>
> and so on?
>

Umm, sure would save us a few lines but it seems to me like we are
trading off readability here. If no one agrees, will change it the way
you pointed out.

> > +
> >                 /* caching the updated state of the low-pass filter */
> >                 st->lpf_3db_freq_idx = lpf_idx;
> >                 /* retrieving the current state of the high-pass filter */
> >                 hpf_idx = st->hpf_3db_freq_idx;
> > -               return adxrs290_set_filter_freq(indio_dev, lpf_idx, hpf_idx);
> > +               ret = adxrs290_set_filter_freq(indio_dev, lpf_idx, hpf_idx);
> > +               break;
> > +
> >         case IIO_CHAN_INFO_HIGH_PASS_FILTER_3DB_FREQUENCY:
> >                 hpf_idx = adxrs290_find_match(adxrs290_hpf_3db_freq_hz_table,
> >                                               ARRAY_SIZE(adxrs290_hpf_3db_freq_hz_table),
> >                                               val, val2);
> > -               if (hpf_idx < 0)
> > -                       return -EINVAL;
> > +               if (hpf_idx < 0) {
> > +                       ret = -EINVAL;
> > +                       break;
> > +               }
> > +
> >                 /* caching the updated state of the high-pass filter */
> >                 st->hpf_3db_freq_idx = hpf_idx;
> >                 /* retrieving the current state of the low-pass filter */
> >                 lpf_idx = st->lpf_3db_freq_idx;
> > -               return adxrs290_set_filter_freq(indio_dev, lpf_idx, hpf_idx);
> > +               ret = adxrs290_set_filter_freq(indio_dev, lpf_idx, hpf_idx);
> > +               break;
> > +
> > +       default:
> > +               ret = -EINVAL;
> > +               break;
> >         }
> >
> > -       return -EINVAL;
> > +       iio_device_release_direct_mode(indio_dev);
> > +       return ret;
> >  }
>
> ...
>
> > +static irqreturn_t adxrs290_trigger_handler(int irq, void *p)
> > +{
>
> > +       /* exercise a bulk data capture starting from reg DATAX0... */
> > +       ret = spi_write_then_read(st->spi, &tx, sizeof(tx), st->buffer.channels,
> > +                                 sizeof(st->buffer.channels));
> > +       if (ret < 0)
> > +               goto done;
> > +
> > +       iio_push_to_buffers_with_timestamp(indio_dev, &st->buffer,
> > +                                          pf->timestamp);
> > +
> > +done:
>
> out_unlock_notify:
>

Okay.

> > +       mutex_unlock(&st->lock);
> > +       iio_trigger_notify_done(indio_dev->trig);
> > +
> > +       return IRQ_HANDLED;
> > +}
>
> ...
>
> > +static int adxrs290_probe_trigger(struct iio_dev *indio_dev)
> > +{
> > +       struct adxrs290_state *st = iio_priv(indio_dev);
> > +       int ret;
>
> > +       if (!st->spi->irq) {
> > +               dev_info(&st->spi->dev, "no irq, using polling\n");
> > +               return 0;
> > +       }
>
> Wouldn't it be better to have this check outside of the function?

I think this function making an early exit makes more sense. The
CHIP_probe() looks less "noisy" that way.

> And taking this into account...
>
> > +}
>
> ...
>
> > +       ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev,
> > +                                             &iio_pollfunc_store_time,
> > +                                             &adxrs290_trigger_handler, NULL);
> > +       if (ret < 0)
> > +               return dev_err_probe(&spi->dev, ret,
> > +                                    "iio triggered buffer setup failed\n");
>
> ...do you really have to set up a trigger buffer w/o trigger being probed?
>

I suppose one can use software triggers like hrtimer and sysfs-trig...

With regards,
Nishant Malpani

> > +       ret = adxrs290_probe_trigger(indio_dev);
> > +       if (ret < 0)
> > +               return ret;
>
> --
> With Best Regards,
> Andy Shevchenko