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SubjectRe: [PATCH 2/2] iio: chemical: Add driver support for sgp40
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On 7/31/21 9:39 AM, Jonathan Cameron wrote:
> On Tue, 27 Jul 2021 18:35:19 +0200
> Andreas Klinger <ak@it-klinger.de> 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@it-klinger.de>
>
> 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.

Guenter

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