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

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Date:   Sat, 2 Mar 2019 19:07:16 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     "Ardelean, Alexandru" <Alex.Ardelean@...log.com>
Cc:     "lars@...afoo.de" <lars@...afoo.de>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "Popa, Stefan Serban" <StefanSerban.Popa@...log.com>,
        "knaack.h@....de" <knaack.h@....de>,
        "Hennerich, Michael" <Michael.Hennerich@...log.com>,
        "renatogeh@...il.com" <renatogeh@...il.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "giuliano.belinassi@....br" <giuliano.belinassi@....br>,
        "pmeerw@...erw.net" <pmeerw@...erw.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "kernel-usp@...glegroups.com" <kernel-usp@...glegroups.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 3/9] staging: iio: ad7780: set pattern values and
 masks directly

On Fri, 1 Mar 2019 07:17:04 +0000
"Ardelean, Alexandru" <Alex.Ardelean@...log.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@...il.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.

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
> >