linux-kernel - Re: Re: [PATCH v2 1/2] iio: adc: ad7291: convert to device tree

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Date:   Tue, 31 Mar 2020 13:56:32 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Michael Auchter <michael.auchter@...com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Stefan Popa <stefan.popa@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>
Subject: Re: Re: [PATCH v2 1/2] iio: adc: ad7291: convert to device tree

On Mon, Mar 30, 2020 at 11:12 PM Michael Auchter <michael.auchter@...com> wrote:
> On Sun, Mar 22, 2020 at 01:46:21AM +0200, Andy Shevchenko wrote:
> > On Tue, Mar 17, 2020 at 4:53 PM Michael Auchter <michael.auchter@...com> wrote:

...

> > > +       chip->reg = devm_regulator_get_optional(&client->dev, "vref");
> > > +       if (!IS_ERR(chip->reg)) {
> >
> > Why not to go with usual positive conditional?
>
> I took this pattern from ad7266.c which Lars pointed me to. I agree that
> a positive conditional here would probably be more natural. I'll change
> that if you'd prefer.

Yes, please do.

...

> > > +               .of_match_table = of_match_ptr(ad7291_of_match),
> >
> > No need to use of_match_ptr(). Haven't you got a compiler warning in !OF case?
>
> Hm, no warning as far as I can see with !OF...

Have you used `make W=1 ...`? With it you should get a warning that
table defined but not used.

> but agreed that this
> doesn't make much sense as-is.
>
> Is dropping of_match_ptr() the preferred route here? The driver doesn't
> depend on OF, so it seems like keeping of_match_ptr and instead guarding
> the ad7291_of_match table with #ifdef CONFIG_OF would be preferred. Of
> course, maybe that's not worth it for saving some bytes from the final
> image.

You need either both (of_match_ptr() _and_ ugly ifdeffery, and note
you will need of.h for that) or none (mod_devicetable.h maybe needed,
though).

> Let me know which route would be preferred.

If we would like to use this in non-DT environment, then drop all that
OF-specific stuff.

-- 
With Best Regards,
Andy Shevchenko