From: Jonathan Cameron <jic23@kernel.org>
To: Dan Robertson <dan@dlrobertson.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
linux-iio <linux-iio@vger.kernel.org>,
Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
devicetree <devicetree@vger.kernel.org>,
Hartmut Knaack <knaack.h@gmx.de>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [PATCH v4 2/2] iio: (bma400) add driver for the BMA400
Date: Sat, 23 Nov 2019 12:51:35 +0000 [thread overview]
Message-ID: <20191123125135.4c7efcb0@archlinux> (raw)
In-Reply-To: <20191118002504.GA29469@nessie>
On Mon, 18 Nov 2019 00:25:04 +0000
Dan Robertson <dan@dlrobertson.com> wrote:
> Sorry for the incredibly late reply. Before I submit the next patchset version,
> I have a question from the last set of reviews.
>
> On Mon, Oct 21, 2019 at 04:20:16PM +0100, Jonathan Cameron wrote:
> > On Sat, 19 Oct 2019 02:43:51 +0000
> > Dan Robertson <dan@dlrobertson.com> wrote:
> > > On Fri, Oct 18, 2019 at 10:23:38AM +0300, Andy Shevchenko wrote:
> > > > On Fri, Oct 18, 2019 at 6:44 AM Dan Robertson <dan@dlrobertson.com> wrote:
> > > > > +static const int bma400_osr_table[] = { 0, 1, 3 };
> > > >
> > > > > +/* See the ACC_CONFIG1 section of the datasheet */
> > > > > +static const int bma400_sample_freqs[] = {
> > > > > + 12, 500000,
> > > > > + 25, 0,
> > > > > + 50, 0,
> > > > > + 100, 0,
> > > > > + 200, 0,
> > > > > + 400, 0,
> > > > > + 800, 0,
> > > > > +};
> > > >
> > > > This can be replaced by a formula(s).
> > >
> > > Yeah I think I can implement the get, set, and read functions for sample_freq
> > > with a formula, but the scale and sample frequency tables are needed by the
> > > implementation of read_avail. A implementation of read_avail with a range and
> > > a step would be ideal, but I couldn't find any documentation on implementing
> > > read_avail where the step value of the range is a multiple. Please correct
> > > me if I've missed something.
> >
> > Indeed. We've only defined it as being fixed intervals.
> > I'm not keen to expand the options for the userspace interface any
> > further.
> >
> > You could compute the values at startup and store it in your state structure
> > I think (or compute them on demand, but you'd need to have the space somewhere
> > non volatile).
> >
>
> I ended up writing an implementation that uses a formula for the get/set
> functions of the sample frequency and scale, but uses a table for the
> implementation of the read_avail function. While it does work, I worry
> that this makes the driver less maintainable and would make it harder to
> add support for a new hypothetical future BMA4xx device. Also, the majority
> of drivers seem to use a table for the raw value to user input conversion,
> so a move from this might make the code less "familiar".
>
> If we do stick with the translation table, would it be better to have two
> tables (a translation table and a read_avail table) so that we do not have
> a step distance of two? This would mean we would need to maintain two
> tables, but would simplify the code.
If a function is your preferred route you could also just use it to compute
the values for the available table at startup?
Otherwise, its fine to just use a table for both.
>
> Random workflow question:
>
> The sampling ratio, frequency, etc code seems to be the most complicated part
> of the driver. Is it typically recommended to upstream a more minimal driver
> that might assume the defaults?
Often people upstream a first version that just uses defaults, then follow
up (if they care) with later series adding the more fiddly elements.
Sometimes those more fiddly bits never come as a particular author
never needed them. That's absolutely fine. It's a rare driver
that supports all the features on a non trivial device!
Thanks,
Jonathan
>
> Cheers,
>
> - Dan
>
next prev parent reply other threads:[~2019-11-23 12:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 3:18 [PATCH v3 0/2] iio: add driver for Bosch BMA400 accelerometer Dan Robertson
2019-10-18 3:18 ` [PATCH v4 1/2] dt-bindings: iio: accel: bma400: add bindings Dan Robertson
2019-10-25 16:35 ` Rob Herring
2019-10-18 3:18 ` [PATCH v4 2/2] iio: (bma400) add driver for the BMA400 Dan Robertson
2019-10-18 4:25 ` Randy Dunlap
2019-10-19 1:35 ` Dan Robertson
2019-10-18 7:23 ` Andy Shevchenko
2019-10-19 2:43 ` Dan Robertson
2019-10-21 15:20 ` Jonathan Cameron
2019-11-18 0:25 ` Dan Robertson
2019-11-23 12:51 ` Jonathan Cameron [this message]
2019-11-24 22:37 ` Dan Robertson
2019-10-19 4:25 ` Joe Perches
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191123125135.4c7efcb0@archlinux \
--to=jic23@kernel.org \
--cc=andy.shevchenko@gmail.com \
--cc=dan@dlrobertson.com \
--cc=devicetree@vger.kernel.org \
--cc=knaack.h@gmx.de \
--cc=linux-iio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=pmeerw@pmeerw.net \
--cc=rdunlap@infradead.org \
--cc=robh+dt@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).