linux-kernel - Re: [PATCH 2/2] of/platform: Disable generic device linking code for PowerPC

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Message-ID: <CAL_JsqLdcn5aZdenLs3RSVCOE1PRNK_qYNmQR=fXPV+ZOQ9+PQ@mail.gmail.com>
Date:   Wed, 14 Aug 2019 17:41:19 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Frank Rowand <frowand.list@...il.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Android Kernel Team <kernel-team@...roid.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] of/platform: Disable generic device linking code for PowerPC

On Tue, Aug 6, 2019 at 4:04 PM Saravana Kannan <saravanak@...gle.com> wrote:
>
> On Tue, Aug 6, 2019 at 2:27 PM Rob Herring <robh+dt@...nel.org> wrote:
> >
> > On Tue, Aug 6, 2019 at 1:27 PM Saravana Kannan <saravanak@...gle.com> wrote:
> > >
> > > PowerPC platforms don't use the generic of/platform code to populate the
> > > devices from DT.
> >
> > Yes, they do.
>
> No they don't. My wording could be better, but they don't use
> of_platform_default_populate_init()
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/of/platform.c#n511

Right, but the rest of the of/platform code is used (guess where it
got moved here from?).

> > > Therefore the generic device linking code is never used
> > > in PowerPC.  Compile it out to avoid warning about unused functions.
> >
> > I'd prefer this get disabled on PPC using 'if (IS_ENABLED(CONFIG_PPC))
> > return' rather than #ifdefs.
>
> I'm just moving the existing ifndef some lines above. I don't want to
> go change existing #ifndef in this patch. Maybe that should be a
> separate patch series that goes and fixes all such code in drivers/of/
> or driver/

So the initcall was originally just supposed to call
of_platform_default_populate(), but it's grown beyond that. That could
make things fragile as it is possible for platforms to call
of_platform_populate() (directly or indirectly) before
of_platform_default_populate_init(). That was supposed to work, but
now I think it's getting more fragile.

Anyways, I guess this patch is fine for now.

Rob