linux-kernel - Re: [net-next PATCH v3 09/15] device property: Introduce fwnode_get

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Date:   Fri, 22 Jan 2021 17:34:12 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Calvin Johnson <calvin.johnson@....nxp.com>,
        Grant Likely <grant.likely@....com>,
        Jeremy Linton <jeremy.linton@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Cristi Sovaiala <cristian.sovaiala@....com>,
        Florin Laurentiu Chiculita <florinlaurentiu.chiculita@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Pieter Jansen Van Vuuren <pieter.jansenvv@...boosystems.io>,
        Jon <jon@...id-run.com>,
        Diana Madalina Craciun <diana.craciun@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "linux.cj" <linux.cj@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [net-next PATCH v3 09/15] device property: Introduce fwnode_get_id()

On Wed, Jan 20, 2021 at 9:01 PM Saravana Kannan <saravanak@...gle.com> wrote:
>
> On Wed, Jan 20, 2021 at 11:15 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> > On Wed, Jan 20, 2021 at 7:51 PM Andy Shevchenko
> > <andy.shevchenko@...il.com> wrote:
> > >
> > > On Wed, Jan 20, 2021 at 8:18 PM Rafael J. Wysocki <rafael@...nel.org> wrote:
> > > > On Tue, Jan 12, 2021 at 7:02 PM Andy Shevchenko
> > > > <andy.shevchenko@...il.com> wrote:
> > > > > On Tue, Jan 12, 2021 at 09:30:31AM -0800, Saravana Kannan wrote:
> > > > > > On Tue, Jan 12, 2021 at 5:42 AM Calvin Johnson
> > > > > > <calvin.johnson@....nxp.com> wrote:
> > >
> > > ...
> > >
> > > > > > > +       ret = fwnode_property_read_u32(fwnode, "reg", id);
> > > > > > > +       if (!(ret && is_acpi_node(fwnode)))
> > > > > > > +               return ret;
> > > > > > > +
> > > > > > > +#ifdef CONFIG_ACPI
> > > > > > > +       status = acpi_evaluate_integer(ACPI_HANDLE_FWNODE(fwnode),
> > > > > > > +                                      METHOD_NAME__ADR, NULL, &adr);
> > > > > > > +       if (ACPI_FAILURE(status))
> > > > > > > +               return -EINVAL;
> > > > > > > +       *id = (u32)adr;
> > > > > > > +#endif
> > > > > > > +       return 0;
> > >
> > > > > > Also ACPI and DT
> > > > > > aren't mutually exclusive if I'm not mistaken.
> > > > >
> > > > > That's why we try 'reg' property for both cases first.
> > > > >
> > > > > is_acpi_fwnode() conditional is that what I don't like though.
> > > >
> > > > I'm not sure what you mean here, care to elaborate?
> > >
> > > I meant is_acpi_node(fwnode) in the conditional.
> > >
> > > I think it's redundant and we can simple do something like this:
> > >
> > >   if (ret) {
> > > #ifdef ACPI
> > >     ...
> > > #else
> > >     return ret;
> > > #endif
> > >   }
> > >   return 0;
> > >
> > > --
> >
> > Right, that should work.  And I'd prefer it too.
>
> Rafael,
>
> I'd rather this new function be an ops instead of a bunch of #ifdef or
> if (acpi) checks. Thoughts?

Well, it looks more like a helper function than like an op and I'm not
even sure how many potential users of it will expect that _ADR should
be evaluated in the absence of the "reg" property.

It's just that the "reg" property happens to be kind of an _ADR
equivalent in this particular binding AFAICS.