Re: [PATCH v1 2/2] iio: temperature: add driver support for ti tmp117

[Lars-Peter Clausen]

On 3/21/21 6:07 AM, Lars-Peter Clausen wrote:
> On 3/20/21 7:45 AM, Puranjay Mohan wrote:
> > TMP117 is a Digital temperature sensor with integrated NV memory.
> >
> > Add support for tmp117 driver in iio subsystem.
> >
> > Datasheet:-https://www.ti.com/lit/gpn/tmp117
> >
> > Signed-off-by: Puranjay Mohan <puranjay12@xxxxxxxxx>
>
> This looks good to me. Just two small bits I overlooked during the 
> first review, sorry for that.
>
> > +};
> > +
> > [...]
> > +static int tmp117_read_raw(struct iio_dev *indio_dev,
> > +        struct iio_chan_spec const *channel, int *val,
> > +        int *val2, long mask)
> > +{
> > +    struct tmp117_data *data = iio_priv(indio_dev);
> > +    u16 tmp, off;
> > +
> > +    switch (mask) {
> > +    case IIO_CHAN_INFO_RAW:
> > +        tmp = tmp117_read_reg(data, TMP117_REG_TEMP);
> > +        *val = tmp;
> No need for tmp here. Just directly assign to val.

Actually thinking about this, does the current implementation work 
correctly for negative temperatures?

I think there are two options to fix it. Either cast to s16 or use the 
sign_extend32() function.

Have a look at how the tmp006 driver handles this. It is a good example, 
including the error checking. In general you should check if your I2C 
read failed and return an error in that case rather than a bogus value 
for the measurement. Same for when reading the calibration offset.

Another thing. IIO reports temperature values in milli degrees Celsius. 
I believe in the current implementation the scale is so that it will 
report in degrees Celsius instead.