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

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Date:   Wed, 20 Jan 2021 19:18:39 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        Calvin Johnson <calvin.johnson@....nxp.com>,
        Grant Likely <grant.likely@....com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        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@...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 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:
> > >
> > > Using fwnode_get_id(), get the reg property value for DT node
> > > or get the _ADR object value for ACPI node.
>
> ...
>
> > > +/**
> > > + * fwnode_get_id - Get the id of a fwnode.
> > > + * @fwnode: firmware node
> > > + * @id: id of the fwnode
> > > + *
> > > + * This function provides the id of a fwnode which can be either
> > > + * DT or ACPI node. For ACPI, "reg" property value, if present will
> > > + * be provided or else _ADR value will be provided.
> > > + * Returns 0 on success or a negative errno.
> > > + */
> > > +int fwnode_get_id(struct fwnode_handle *fwnode, u32 *id)
> > > +{
> > > +#ifdef CONFIG_ACPI
> > > +       unsigned long long adr;
> > > +       acpi_status status;
> > > +#endif
> > > +       int ret;
> > > +
> > > +       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;
> > > +}
> > > +EXPORT_SYMBOL_GPL(fwnode_get_id);
>
> > Please don't do it this way. The whole point of fwnode_operations is
> > to avoid conditional stuff at the fwnode level.
>
> Not fully true. We have non-POD getters that are conditional. Moreover,
> we have additional layer of Primary / Secondary fwnodes on top of that.
>
> The caller of fwnode API is indeed agnostic, but under the hood it differs by
> the definition (obviously due to natural differences between ACPI and DT and
> whatever else might come in the future.
>
> > 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?