linux-kernel - Re: [PATCH 11/42] ARM: shmobile: Register PFC platform device

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Message-ID: <20121126010205.GF20490@verge.net.au>
Date:	Mon, 26 Nov 2012 10:02:05 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	linux-kernel@...r.kernel.org, Paul Mundt <lethal@...ux-sh.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Phil Edworthy <phil.edworthy@...esas.com>,
	Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@...esas.com>
Subject: Re: [PATCH 11/42] ARM: shmobile: Register PFC platform device

On Wed, Nov 21, 2012 at 01:43:15PM +0100, Laurent Pinchart wrote:
> Hi Simon,
> 
> On Wednesday 21 November 2012 14:16:33 Simon Horman wrote:
> > On Wed, Nov 21, 2012 at 03:27:12AM +0100, Laurent Pinchart wrote:
> > > Add arch code to register the PFC platform device instead of calling the
> > > driver directly. Platform device registration in the sh-pfc driver will
> > > be removed.
> > 
> > I'm not really sure that I understand the motivation for
> > moving platform device registration from the driver into
> > mach-shmobile. Could you explain this a little?
> 
> Sure.
> 
> The traditional device model associates a driver with a device. For historical 
> reasons mach-shmobile doesn't define and register a platform device for PFC 
> hardware but calls an initialization function directly in the PFC driver, 
> passing it what is essentially platform data, including resources.
> 
> The PFC driver needs a struct device to pass to the pinctrl subsystem. As no 
> struct device corresponding to the hardware is created by mach-shmobile, the 
> driver creates one, registers it and registers itself as a platform driver. 
> The probe function is thus called synchronously, with a valid struct 
> platform_device.
> 
> This is a hack that can't support device tree based instantiation, as the 
> platform device will be created when the platform is populated from the DT in 
> that case. To support DT (and to remove the hack), I've moved platform device 
> registration to mach-shmobile as it should be, like already done for all (or 
> most, I haven't checked if there's no similar hacks in other drivers) the 
> platform devices. This allows converting a board to DT by just adding the PFC 
> device node in the DT and removing the platform device registration call in 
> board code.
> 
> I hope this made the intend of this part of the patch series clear. If not, 
> just tell me and I'll try to provide more explanations.

Thanks Laurent,

as it happens I was doing some work on pinmux and DT in as part of
my kzm9g series, so what you describe above now makes a lot of sense to me.

For this and all the other shmobile patches in this series:

Acked-by: Simon Horman <horms@...ge.net.au>


BTW, my kzm9g work is not intended to conflict with your work in any way
and I apologise if it does. I was just trying to make something quickly to
allow kzm9g DT work to move a little further forward. I very much welcome
your work in this area and naturally the kzm9g will use it once it is ready.

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