linux-kernel - Re: [PATCH 2/3] i2c: slave-mqueue: add a slave backend to receive and queue messages

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Message-ID: <CAHp75VfPYC7xDfsGRZsSy8eV1xoMANsVmyuU_yF0kPG0fMtLCQ@mail.gmail.com>
Date:   Wed, 5 Jun 2019 18:58:54 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Eduardo Valentin <eduval@...zon.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Haiyue Wang <haiyue.wang@...ux.intel.com>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] i2c: slave-mqueue: add a slave backend to receive and
 queue messages

On Wed, Jun 5, 2019 at 6:31 PM Eduardo Valentin <eduval@...zon.com> wrote:
> On Wed, Jun 05, 2019 at 06:20:37PM +0300, Andy Shevchenko wrote:
> > On Wed, Jun 5, 2019 at 5:32 PM Eduardo Valentin <eduval@...zon.com> wrote:
> > > On Wed, Jun 05, 2019 at 11:25:39AM +0300, Andy Shevchenko wrote:
> > > > On Wed, Jun 5, 2019 at 6:30 AM Eduardo Valentin <eduval@...zon.com> wrote:

> > > > > > > +           .of_match_table = of_match_ptr(i2c_slave_mqueue_of_match),
> > > > > >
> > > > > > Wouldn't compiler warn you due to unused data?
> > > > > > Perhaps drop of_match_ptr() for good...
> > > > >
> > > > > Not sure what you meant here. I dont see any compiler warning.
> > > > > Also, of_match_ptr seams to be well spread in the kernel.
> > > >
> > > > If this will be compiled with CONFIG_OF=n...
> > >
> > > I see.. I obviously did not test with that config..
> > >
> > > > Though I didn't check all dependencies to see if it even possible. In
> > > > any case of_match_ptr() is redundant in both cases here.
> > > > Either you need to protect i2c_slave_mqueue_of_match with #ifdef
> > > > CONFIG_OF, or drop the macro use.
> > >
> > > I will wrap it into CONFIG_OF..
> >
> > Would be this expected to work in the case of CONFIG_OF=n?
> > If no, why to introduce ugly #ifdef:s and additional macros?
>
> I do hate those too...
>
> > Wouldn't be better to have
> >   depends on OF || COMPILE_TEST
>
> Well, technically, the original author had a case for using this
> without CONFIG_OF. That is why I did not force here to be a strong
> dependency on CONFIG_OF. So, I guess in this case the driver will
> work properly in both cases if we:
>
> +#ifdef CONFIG_OF
> +static const struct of_device_id i2c_slave_mqueue_of_match[] = {
> +       {
> +               .compatible = "i2c-slave-mqueue",
> +       },
> +       { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, i2c_slave_mqueue_of_match);
> +#endif
> +
> +static struct i2c_driver i2c_slave_mqueue_driver = {
> +       .driver = {
> +               .name   = "i2c-slave-mqueue",
> +               .of_match_table = of_match_ptr(i2c_slave_mqueue_of_match),
> +       },
> +       .probe          = i2c_slave_mqueue_probe,
> +       .remove         = i2c_slave_mqueue_remove,
> +       .id_table       = i2c_slave_mqueue_id,
> +};
>
> The above is a well stablish pattern across the drivers.

My point here that you may achieve the same by simple dropping of_match_ptr().

P.S. Many of the drivers just old enough and not being simplified due
to pointless churn there, but for new drivers we may avoid it.

-- 
With Best Regards,
Andy Shevchenko