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From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
CC:     Colin Foster <colin.foster@in-advantage.com>,
        devicetree <devicetree@vger.kernel.org>,
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Subject: Re: [PATCH v11 net-next 1/9] mfd: ocelot: add helper to get regmap
 from a resource
Thread-Topic: [PATCH v11 net-next 1/9] mfd: ocelot: add helper to get regmap
 from a resource
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Date:   Tue, 28 Jun 2022 15:33:21 +0000
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On Tue, Jun 28, 2022 at 02:50:36PM +0200, Andy Shevchenko wrote:
> On Tue, Jun 28, 2022 at 10:17 AM Colin Foster
> <colin.foster@in-advantage.com> wrote:
> >
> > Several ocelot-related modules are designed for MMIO / regmaps. As such=
,
> > they often use a combination of devm_platform_get_and_ioremap_resource =
and
> > devm_regmap_init_mmio.
> >
> > Operating in an MFD might be different, in that it could be memory mapp=
ed,
> > or it could be SPI, I2C... In these cases a fallback to use IORESOURCE_=
REG
> > instead of IORESOURCE_MEM becomes necessary.
> >
> > When this happens, there's redundant logic that needs to be implemented=
 in
> > every driver. In order to avoid this redundancy, utilize a single funct=
ion
> > that, if the MFD scenario is enabled, will perform this fallback logic.
>=20
> > +       regs =3D devm_platform_get_and_ioremap_resource(pdev, index, &r=
es);
> > +
> > +       if (!res)
> > +               return ERR_PTR(-ENOENT);
>=20
> This needs a comment why the original error code from devm_ call above
> is not good here.

I think what is really needed is an _optional() variant of
ocelot_platform_init_regmap_from_resource(), which just returns NULL on
missing resource and doesn't ioremap anything. It can be easily open
coded, i.e. instead of creating devm_platform_get_and_ioremap_resource_opti=
onal(),
we could just call platform_get_resource() and devm_ioremap_resource()
individually.=