On Sat, 31 Jul 2021 11:06:25 -0700
Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> On 7/31/21 9:39 AM, Jonathan Cameron wrote:
> > On Tue, 27 Jul 2021 18:35:19 +0200
> > Andreas Klinger <ak@xxxxxxxxxxxxx> wrote:
> >
> >> sgp40 is a gas sensor used for measuring the air quality.
> >>
> >> This driver is reading the raw resistance value which can be passed to
> >> a userspace algorithm for further calculation.
> >>
> >> The raw value is also used to calculate an estimated absolute voc index
> >> in the range from 0 to 500. For this purpose the raw_mean value of the
> >> resistance for which the index value is 250 might be set up as a
> >> calibration step.
> >>
> >> Compensation of relative humidity and temperature is supported and can
> >> be used by writing to device attributes of the driver.
> >>
> >> There is a predecesor sensor type (sgp30) already existing. This driver
> >> module was not extended because the new sensor is quite different in its
> >> i2c telegrams.
> >>
> >> Signed-off-by: Andreas Klinger <ak@xxxxxxxxxxxxx>
> >
> > Hi Andreas,
> >
> > Non standard ABI in here, so we are missing documentation in Documentation/ABI/testing/sysfs-bus-iio-*
> >
> > Otherwise a few suggestions inline.
> >
> > Thanks,
> >
> > Jonathan
> >
> >
> >> ---
> [ ... ]
>
> >> +static int sgp40_read_raw(struct iio_dev *indio_dev,
> >> + struct iio_chan_spec const *chan, int *val,
> >> + int *val2, long mask)
> >> +{
> >> + struct sgp40_data *data = iio_priv(indio_dev);
> >> + int ret;
> >> + u16 raw;
> >> + int voc;
> >> +
> >> + switch (mask) {
> >> + case IIO_CHAN_INFO_RAW:
> >> + mutex_lock(&data->lock);
> >> + ret = sgp40_measure_raw(data, &raw);
> >> + if (ret) {
> >> + mutex_unlock(&data->lock);
> >> + return ret;
> >> + }
> >> + *val = raw;
> >> + ret = IIO_VAL_INT;
> >> + mutex_unlock(&data->lock);
> >> + break;
> >> + case IIO_CHAN_INFO_PROCESSED:
> >> + mutex_lock(&data->lock);
> >> + ret = sgp40_measure_raw(data, &raw);
> >> + if (ret) {
> >> + mutex_unlock(&data->lock);
> >> + return ret;
> >> + }
> >> + ret = sgp40_calc_voc(data, raw, &voc);
> >> + if (ret) {
> >> + mutex_unlock(&data->lock);
> >> + return ret;
> >> + }
> >> + *val = voc;
> >> + ret = IIO_VAL_INT;
> >> + mutex_unlock(&data->lock);
> >
> > You are holding the lock longer than needed - it would be good
> > to reduce this, hopefully removing the need for unlocking separately
> > in each of the error paths.
> >
> >> + break;
> >> + default:
> >> + return -EINVAL;
> >> + }
> >> +
> >> + return ret;
> >
> > Drop this as you can't get here.
> >
>
> Are you sure ? I see several "break;" above.
Doh! In that case, return directly where it has break above so we don't
need to go see if anything else happens in those paths.
>
> Guenter
