linux-kernel - Re: [PATCH] gpio: em: Add Device Tree support

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Date:	Thu, 28 Feb 2013 14:11:23 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	Magnus Damm <magnus.damm@...il.com>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-kernel@...r.kernel.org, grant.likely@...retlab.ca,
	linus.walleij@...aro.org, linux-sh@...r.kernel.org
Subject: Re: [PATCH] gpio: em: Add Device Tree support

On Wed, Feb 27, 2013 at 07:13:46PM +0900, Magnus Damm wrote:
> Hi Dmitry,
> 
> Thanks for your feedback!
> 
> On Wed, Feb 27, 2013 at 7:41 AM, Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
> > Hi Magnus,
> >
> > On Tue, Feb 26, 2013 at 10:26:23PM +0900, Magnus Damm wrote:
> >> From: Magnus Damm <damm@...nsource.se>
> >>
> >> Update the Emma Mobile GPIO driver to add DT support.
> >>
> >
> > ...
> >
> >> @@ -366,15 +387,33 @@ static int em_gio_remove(struct platform
> >>       return 0;
> >>  }
> >>
> >
> > #ifdef CONFIG_OF here? No need to have extra aliases in modules if OF
> > support is not enabled (or is entire ARM arch now enables device tree?).
> >
> >> +static const struct of_device_id em_gio_dt_ids[] = {
> >> +     { .compatible = "renesas,em-gio", },
> >> +     {},
> >> +};
> >> +MODULE_DEVICE_TABLE(of, em_gio_dt_ids);
> >> +
> 
> I suppose we could sprinkle a couple of #ifdefs across the code, but I
> have to say that I'm not that fond of #ifdefs in general. So if it was
> up to me only then I would aim at having exactly zero #ifdefs in my
> drivers at the expense of slightly larger binaries in some cases.

My take on this is as follows (if anyone cares):

* The driver in question is currently only useful in conjunction with
  the Emev2 SoC and the kzm9g board which uses that SoC. The current
  (and to date only) practice when booting that board and thus SoC
  with merged upstream code is to do so using DT.

* The inclusion of the code above does not appear to cause build-time
  breakage even if CONFIG_OF is not set.

So it seems to me that it is reasonable to leave the code as is
without being guarded by an #ifdef.
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