linux-kernel - Re: [PATCH] platform: set of_node in platform_device_register

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Date:   Wed, 20 Feb 2019 22:50:00 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Måns Rullgård <mans@...sr.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform: set of_node in platform_device_register_full()

On Wed, Feb 20, 2019 at 1:26 PM Måns Rullgård <mans@...sr.com> wrote:
>
> "Rafael J. Wysocki" <rafael@...nel.org> writes:
>
> > On Wed, Feb 20, 2019 at 1:12 PM Måns Rullgård <mans@...sr.com> wrote:
> >>
> >> Johan Hovold <johan@...nel.org> writes:
> >>
> >> > On Wed, Feb 20, 2019 at 11:35:06AM +0000, Mans Rullgard wrote:
> >> >> If the provided fwnode is an OF node, set dev.of_node as well.
> >> >>
> >> >> Some drivers are just shims that create extra "glue" devices with the
> >> >> DT device as parent and have the real driver bind to these.  In these
> >> >> cases, the glue device needs to get a reference to the original DT node
> >> >> in order for the main driver to access properties and child nodes.
> >> >>
> >> >> For example, the sunxi-musb driver creates such a glue device using
> >> >> platform_device_register_full().  Consequently, devices attached to
> >> >> this USB interface don't get associated with DT nodes, if present,
> >> >> the way they do with EHCI.
> >> >>
> >> >> This change will allow sunxi-musb and similar driver to easily
> >> >> propagate the DT node to child devices as required.
> >> >
> >> > Just a drive-by comment, didn't look to closely at this patch, but this
> >> > all sounds familiar.
> >> >
> >> > Note that if both platform devices are bound to drivers you may end up
> >> > with some resources like pinctrl which are handled automatically by
> >> > driver core at probe time to be requested twice (and failing the second
> >> > time).
> >> >
> >> > Take a look at 4e75e1d7dac9 ("driver core: add helper to reuse a
> >> > device-tree node"), which provides a means to avoid this, and
> >> > 49484abd93ab ("USB: musb: dsps: propagate device-tree node").
> >>
> >> Thanks, and ugh.  So we should be setting the of_node_reused flag when
> >> this is the case.  It's easy for the musb-dsps driver since it doesn't
> >> use platform_device_register_full() and can do this before the
> >> device_add() call.  How can we convey that this flag needs to be set?
> >
> > Through pdevinfo I guess?
>
> Not without adding another field to it.  The most direct is of course to
> simply add an of_node_reused flag there too and copy it over.  Would
> that be OK, or is there a better way?

That's what I meant. :-)