Re: [PATCH v4 4/9] staging:iio:ad7780: add chip ID values and mask

[Renato Lui Geh]

On 03/04, Ardelean, Alexandru wrote:
> On Sun, 2019-03-03 at 14:53 +0000, Jonathan Cameron wrote:
> > [External]
> >
> >
> > On Sun, 3 Mar 2019 11:01:09 -0300
> > Renato Lui Geh <renatogeh@xxxxxxxxx> wrote:
> >
> > > On 03/01, Ardelean, Alexandru wrote:
> > > > On Thu, 2019-02-28 at 11:24 -0300, Renato Lui Geh wrote:
> > > > >
> > > > >
> > > > > The ad7780 supports both the ad778x and ad717x families. Each chip
> > > > > has
> > > > > a corresponding ID. This patch provides a mask for extracting ID
> > > > > values
> > > > > from the status bits and also macros for the correct values for the
> > > > > ad7170, ad7171, ad7780 and ad7781.
> > > > >
> > > > > Signed-off-by: Renato Lui Geh <renatogeh@xxxxxxxxx>
> > > > > ---
> > > > >  drivers/staging/iio/adc/ad7780.c | 8 ++++++--
> > > > >  1 file changed, 6 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/staging/iio/adc/ad7780.c
> > > > > b/drivers/staging/iio/adc/ad7780.c
> > > > > index 56c49e28f432..ad7617a3a141 100644
> > > > > --- a/drivers/staging/iio/adc/ad7780.c
> > > > > +++ b/drivers/staging/iio/adc/ad7780.c
> > > > > @@ -26,10 +26,14 @@
> > > > >  #define AD7780_RDY             BIT(7)
> > > > >  #define AD7780_FILTER          BIT(6)
> > > > >  #define AD7780_ERR             BIT(5)
> > > > > -#define AD7780_ID1             BIT(4)
> > > > > -#define AD7780_ID0             BIT(3)
> > > > >  #define AD7780_GAIN            BIT(2)
> > > > >
> > > > > +#define AD7170_ID              0
> > > > > +#define AD7171_ID              1
> > > > > +#define AD7780_ID              1
> > > > > +#define AD7781_ID              0
> > > > > +
> > > > > +#define AD7780_ID_MASK         (BIT(3) | BIT(4))
> > > >
> > > > This also doesn't have any functionality change.
> > > > The AD7170_ID, AD7171_ID, AD7780_ID & AD7781_ID IDs are also unused
> > > > (maybe
> > > > in a later patch they are ?).
> > >
> > > They aren't. I added them following a previous review suggestion.
> > > Should
> > > I remove them?
> >
> > Can we check them?  It's always useful to confirm that the device is
> > the one you think it is.  Then we can either use what is there
> > with a suitable warning, or if that is tricky just fault out as the
> > dt is giving us the wrong part number.
> >
> > J
>
> I guess `dev_warn_ratelimited()` could be used to make sure syslog isn't
> spammed-to-death when doing multiple conversions, and the ID isn't correct.
> Since these IDs are read after you get a sample, I'm a bit fearful of log-
> spam.
>
> I wouldn't throw an error in the ad7780_postprocess_sample() for this, but
> warning [with rate-limit] sounds reasonable.

Looking at dev_warn_ratelimited's definition (and its use in other parts
of the kernel), I see that we'd need the device to be stored somewhere
(perhaps in ad7780_state?) in order for us to pass it as argument to
dev_warn from within postprocess_sample. Should this be stored in
ad7780_state?  Or can I get the spi_device some other way?
> > > >
> > > > I would also leave the AD7780_ID1 & AD7780_ID0 definitions in place,
> > > > since
> > > > they're easier matched with the datasheet.
> > > >
> > > > >
> > > > >  #define AD7780_PATTERN_GOOD    1
> > > > >  #define AD7780_PATTERN_MASK    GENMASK(1, 0)
> > > > > --
> > > > > 2.21.0
> > > > >