linux-kernel - Re: [PATCH v5 1/5] iio: adc: ad7949: define and use bitfield names

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Date:   Mon, 09 Aug 2021 13:03:10 -0700
From:   Joe Perches <joe@...ches.com>
To:     Liam Beguin <liambeguin@...il.com>, lars@...afoo.de,
        Michael.Hennerich@...log.com, jic23@...nel.org,
        charles-antoine.couret@...ensium.com, Nuno.Sa@...log.com
Cc:     linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, robh+dt@...nel.org
Subject: Re: [PATCH v5 1/5] iio: adc: ad7949: define and use bitfield names

On Sun, 2021-08-08 at 18:46 -0400, Liam Beguin wrote:
> On Sun Aug 8, 2021 at 12:51 PM EDT, Joe Perches wrote:
> > On Sat, 2021-08-07 at 21:56 -0400, Liam Beguin wrote:
> > > Replace raw configuration register values by using FIELD_PREP and
> > > defines to improve readability.
> > []
> > > diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> > []
> > +#define AD7949_CFG_BIT_INCC GENMASK(12, 10)
> > 
> 
> Hi Joe,
> 
> > I think the naming is a bit confusing as it appears as if
> > these bitfield ranges are single bits.
> 
> That makes sense.
> Would AD7949_CFG_BITS_* be good enough?

Sure, or add MASK or something else like AD7949_CFG_MASK_INCC.

It's pretty common to define _MASK and _SHIFT for these types
of uses.

For instance:
include/drm/drm_dp_helper.h-# define DP_DSC_MAJOR_MASK                  (0xf << 0)
include/drm/drm_dp_helper.h-# define DP_DSC_MINOR_MASK                  (0xf << 4)
include/drm/drm_dp_helper.h:# define DP_DSC_MAJOR_SHIFT                 0
include/drm/drm_dp_helper.h:# define DP_DSC_MINOR_SHIFT                 4