linux-kernel - Re: [PATCH v2 05/22] iio: accel: adxl345: measure right-justified

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Message-ID: <CAFXKEHZdp7cSnE8fj8y9ek0x6zev3Up918B-Ox=WS0bv9KhviA@mail.gmail.com>
Date: Tue, 26 Nov 2024 14:51:19 +0100
From: Lothar Rubusch <l.rubusch@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: lars@...afoo.de, Michael.Hennerich@...log.com, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, eraretuya@...il.com
Subject: Re: [PATCH v2 05/22] iio: accel: adxl345: measure right-justified

Dear IIO Mailing-List, Hi Jonathan!

Thank you so much for the review. As you probably saw, most (all?) of
my commits have a huge invisible question mark attached. Most of my
questions you answered clearly. On particular topics I'd like to get
back, though. Generally I will try to apply the requested changes to
best of my understanding.

On Sun, Nov 24, 2024 at 7:07 PM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Sun, 17 Nov 2024 18:26:34 +0000
> Lothar Rubusch <l.rubusch@...il.com> wrote:
>
> > Make measurements right-justified, since it is the default for the
> > driver and sensor. By not setting the ADXL345_DATA_FORMAT_JUSTIFY bit,
> > the data becomes right-judstified. This was the original setting, there
> > is no reason to change it to left-justified, where right-justified
> > simplifies working on the registers.
>
> Surely this can't be changed independent of other changes as it will
> change the format of the data we are processing?
>
> Each change must stand on it's own so that I can apply up to any
> point in your patch set and have everything continue to work.

This is probably not quite clear. Originally the driver was
right-justified. One of my last commits
(f68ebfe1501bf1110eebf5e968c4d9186cba8706) changed the driver to work
with left-justified measurements. So, I feel changing the orginal
behavior is wrong, and here I try to re-establish the original driver
behavior.

When looking at the datasheet right-justified data seems to be easier
to handle, but I don't have any personal preference.

Lothar

[...]
> > ---
> >  drivers/iio/accel/adxl345_core.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iio/accel/adxl345_core.c b/drivers/iio/accel/adxl345_core.c
> > index 2b62e79248..926e397678 100644
> > --- a/drivers/iio/accel/adxl345_core.c
> > +++ b/drivers/iio/accel/adxl345_core.c
> > @@ -184,8 +184,13 @@ int adxl345_core_probe(struct device *dev, struct regmap *regmap,
> >       struct adxl34x_state *st;
> >       struct iio_dev *indio_dev;
> >       u32 regval;
> > +
> > +     /* NB: ADXL345_DATA_FORMAT_JUSTIFY or 0:
>         /*
>          * NB: AD...
>
> is the multiline comment style all IIO drivers use (and most of the kernel
> except for networking.
>
> > +      * do right-justified: 0, then adjust resolution according to 10-bit
> > +      * through 13-bit in channel - this is the default behavior, and can
> > +      * be modified here by oring ADXL345_DATA_FORMAT_JUSTIFY
> > +      */
> >       unsigned int data_format_mask = (ADXL345_DATA_FORMAT_RANGE |
> > -                                      ADXL345_DATA_FORMAT_JUSTIFY |
> >                                        ADXL345_DATA_FORMAT_FULL_RES |
> >                                        ADXL345_DATA_FORMAT_SELF_TEST);
> >       int ret;
>