Re: [PATCH v4 3/9] staging: iio: ad7780: set pattern values and masks directly

[Jonathan Cameron <jic23@jic23.retrosnub.co.uk>]

On Sat, 2 Mar 2019 19:07:16 +0000
Jonathan Cameron <jic23@kernel.org> wrote:

> On Fri, 1 Mar 2019 07:17:04 +0000
> "Ardelean, Alexandru" <Alex.Ardelean@analog.com> wrote:
> 
> > On Thu, 2019-02-28 at 11:24 -0300, Renato Lui Geh wrote:  
> > > 
> > > 
> > > The AD7780 driver contains status pattern bits designed for checking
> > > whether serial transfers have been correctly performed. Pattern macros
> > > were previously generated through bit fields. This patch sets good
> > > pattern values directly and masks through GENMASK.
> > > 
> > > Signed-off-by: Renato Lui Geh <renatogeh@gmail.com>
> > > ---
> > >  drivers/staging/iio/adc/ad7780.c | 20 +++++++++-----------
> > >  1 file changed, 9 insertions(+), 11 deletions(-)
> > > 
> > > diff --git a/drivers/staging/iio/adc/ad7780.c
> > > b/drivers/staging/iio/adc/ad7780.c
> > > index 7a68e90ddf14..56c49e28f432 100644
> > > --- a/drivers/staging/iio/adc/ad7780.c
> > > +++ b/drivers/staging/iio/adc/ad7780.c
> > > @@ -17,6 +17,7 @@
> > >  #include <linux/sched.h>
> > >  #include <linux/gpio/consumer.h>
> > >  #include <linux/module.h>
> > > +#include <linux/bits.h>
> > > 
> > >  #include <linux/iio/iio.h>
> > >  #include <linux/iio/sysfs.h>
> > > @@ -28,16 +29,13 @@
> > >  #define AD7780_ID1             BIT(4)
> > >  #define AD7780_ID0             BIT(3)
> > >  #define AD7780_GAIN            BIT(2)
> > > -#define AD7780_PAT1            BIT(1)
> > > -#define AD7780_PAT0            BIT(0)    
> > 
> > I don't see a problem to leave the bitfields;  they can be read & matched
> > easier with the datasheet.
> >   
> > > 
> > > -#define AD7780_PATTERN         (AD7780_PAT0)
> > > -#define AD7780_PATTERN_MASK    (AD7780_PAT0 | AD7780_PAT1)
> > > 
> > > -#define AD7170_PAT2            BIT(2)    
> >   
> > > +#define AD7780_PATTERN_GOOD    1    
> > 
> > It was also nice before that the PAT0..PAT2 bitfields were used to define a
> > good pattern, since it's easier to match with the datasheet.  
> This one was much suggestion.  Not particularly important one.
Not enough sleep this week clearly :)  
This one was _my_ suggestion.

> 
> Personally if a datasheet is pointlessly confusing I tend to ignore it.
> This is a two bit field as the bits don't have independent meaning!
> 
> I'm not strongly tied to it though and as it's an Analog driver and
> you all do a good job maintaining the set I'll go with your preference!
> I do prefer the naming of PATTERN_GOOD though if nothing else!
> > 
> >   
> > > +#define AD7780_PATTERN_MASK    GENMASK(1, 0)    
> > 
> > I like the general usage of GENMASK, but I'm not sure in this case it's
> > worth doing. Maybe I missed a discussion somewhere, about doing this
> > change, but it is mostly a cosmetic without any functional change.
> > 
> >   
> > > 
> > > -#define AD7170_PATTERN         (AD7780_PAT0 | AD7170_PAT2)
> > > -#define AD7170_PATTERN_MASK    (AD7780_PAT0 | AD7780_PAT1 | AD7170_PAT2)
> > > +#define AD7170_PATTERN_GOOD    5
> > > +#define AD7170_PATTERN_MASK    GENMASK(2, 0)
> > > 
> > >  #define AD7780_GAIN_MIDPOINT   64
> > >  #define AD7780_FILTER_MIDPOINT 13350
> > > @@ -209,25 +207,25 @@ static const struct ad_sigma_delta_info
> > > ad7780_sigma_delta_info = {
> > >  static const struct ad7780_chip_info ad7780_chip_info_tbl[] = {
> > >         [ID_AD7170] = {
> > >                 .channel = AD7170_CHANNEL(12, 24),
> > > -               .pattern = AD7170_PATTERN,
> > > +               .pattern = AD7170_PATTERN_GOOD,
> > >                 .pattern_mask = AD7170_PATTERN_MASK,
> > >                 .is_ad778x = false,
> > >         },
> > >         [ID_AD7171] = {
> > >                 .channel = AD7170_CHANNEL(16, 24),
> > > -               .pattern = AD7170_PATTERN,
> > > +               .pattern = AD7170_PATTERN_GOOD,
> > >                 .pattern_mask = AD7170_PATTERN_MASK,
> > >                 .is_ad778x = false,
> > >         },
> > >         [ID_AD7780] = {
> > >                 .channel = AD7780_CHANNEL(24, 32),
> > > -               .pattern = AD7780_PATTERN,
> > > +               .pattern = AD7780_PATTERN_GOOD,
> > >                 .pattern_mask = AD7780_PATTERN_MASK,
> > >                 .is_ad778x = true,
> > >         },
> > >         [ID_AD7781] = {
> > >                 .channel = AD7780_CHANNEL(20, 32),
> > > -               .pattern = AD7780_PATTERN,
> > > +               .pattern = AD7780_PATTERN_GOOD,
> > >                 .pattern_mask = AD7780_PATTERN_MASK,
> > >                 .is_ad778x = true,
> > >         },
> > > --
> > > 2.21.0
> > >     
>