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

[Nishant Malpani]

Hello,

Thanks for the review, Andy. Comments inline...

On 26/08/20 9:40 pm, Andy Shevchenko wrote:
> On Tue, Aug 25, 2020 at 4:11 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;
> > +
> > +       mutex_lock(&st->lock);
> > +
> > +       if (st->mode == mode) {
>
> > +               ret = 0;
>
> Can be done outside of mutex.
Yep, makes sense.
> > +               goto done;
> > +       }
> > +
>
> > +       val = spi_w8r8(st->spi, ADXRS290_READ_REG(ADXRS290_REG_POWER_CTL));
> > +       if (val < 0) {
> > +               ret = val;
> > +               goto done;
> > +       }
>
> Consider other way around
>   ret = ...
>   ...
>   val = ret;
I suppose that does make things consistent; will do so in v2.

> > +       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:
> > +       mutex_unlock(&st->lock);
> > +       return ret;
> > +}
>
> ...
>
> > +                               goto err_release;
> >
> > -                       return IIO_VAL_INT;
> > +                       ret = IIO_VAL_INT;
> > +                       break;
> >                  default:
> > -                       return -EINVAL;
> > +                       ret = -EINVAL;
> > +                       break;
> >                  }
>
> > +err_release:
>
> I didn't get the purpose of this. Wasn't the break statement enough?
It is indeed; I just thought the labeling was a preferred way to jump to 
error handling paths. Will use just the 'break' in v2.

> > +               iio_device_release_direct_mode(indio_dev);
> > +               return ret;
> >          case IIO_CHAN_INFO_SCALE:
> >                  switch (chan->type) {
> >                  case IIO_ANGL_VEL:
>
> ...
>
> > +                       goto err_release;
>
> Ditto.
Got it.

> > +               }
> > +
> >                  /* 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;
> > +err_release:
> > +       iio_device_release_direct_mode(indio_dev);
> > +       return ret;
> >   }
>
> ...
>
> > +       val = (state ? ADXRS290_SYNC(ADXRS290_DATA_RDY_OUT) : 0);
>
> Purpose of outer parentheses?
> I personally find that more readable but I think I'm violating the 
coding style in the kernel; will remove the parentheses in v2.

> ...
>
> > +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;
> > +       }
> > +
> > +       st->dready_trig = devm_iio_trigger_alloc(&st->spi->dev,
> > +                                                "%s-dev%d",
> > +                                                indio_dev->name,
> > +                                                indio_dev->id);
> > +       if (!st->dready_trig)
> > +               return -ENOMEM;
> > +
> > +       st->dready_trig->dev.parent = &st->spi->dev;
> > +       st->dready_trig->ops = &adxrs290_trigger_ops;
> > +       iio_trigger_set_drvdata(st->dready_trig, indio_dev);
> > +
> > +       ret = devm_request_irq(&st->spi->dev, st->spi->irq,
> > +                              &iio_trigger_generic_data_rdy_poll,
> > +                              IRQF_ONESHOT,
> > +                              "adxrs290_irq", st->dready_trig);
> > +       if (ret < 0) {
>
> > +               dev_err(&st->spi->dev, "request irq %d failed\n", st->spi->irq);
> > +               return ret;
>
> return dev_err_probe(...);
Nice, wasn't aware of this. Thanks. Will use 'dev_err_probe()' in v2 
wherever pointed.

With regards,
Nishant Malpani

> > +       }
> > +
> > +       ret = devm_iio_trigger_register(&st->spi->dev, st->dready_trig);
> > +       if (ret) {
>
> > +               dev_err(&st->spi->dev, "iio trigger register failed\n");
> > +               return ret;
>
> return dev_err_probe(...);
>
> > +       }
> > +
> > +       indio_dev->trig = iio_trigger_get(st->dready_trig);
> > +
> > +       return 0;
> > +}
>
> ...
>
> > +       ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev,
> > +                                             &iio_pollfunc_store_time,
> > +                                             &adxrs290_trigger_handler, NULL);
> > +       if (ret < 0) {
>
> > +               dev_err(&spi->dev, "iio triggered buffer setup failed\n");
> > +               return ret;
>
> return dev_err_probe(...);
>
> > +       }