linux-kernel - Re: [PATCH] Driver Core: Add platform device arch data V3

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Message-Id: <200906251634.12222.rjw@sisk.pl>
Date:	Thu, 25 Jun 2009 16:34:11 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Magnus Damm <magnus.damm@...il.com>
Cc:	linux-kernel@...r.kernel.org, paul@...an.com, gregkh@...e.de,
	khilman@...prootsystems.com, stern@...land.harvard.edu,
	linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH] Driver Core: Add platform device arch data V3

On Thursday 25 June 2009, Magnus Damm wrote:
> On Thu, Jun 25, 2009 at 3:50 AM, Rafael J. Wysocki<rjw@...k.pl> wrote:
> > On Wednesday 24 June 2009, Magnus Damm wrote:
> >> On Fri, Jun 19, 2009 at 1:21 AM, Kevin
> >> Hilman<khilman@...prootsystems.com> wrote:
> >> > Magnus Damm <magnus.damm@...il.com> writes:
> >> >
> >> >> From: Magnus Damm <damm@...l.co.jp>
> >> >>
> >> >> Allow architecture specific data in struct platform_device V3.
> >> >>
> >> >> With this patch struct pdev_archdata is added to struct
> >> >> platform_device, similar to struct dev_archdata in found in
> >> >> struct device. Useful for architecture code that needs to
> >> >> keep extra data associated with each platform device.
> >> >>
> >> >> Struct pdev_archdata is different from dev.platform_data, the
> >> >> convention is that dev.platform_data points to driver-specific
> >> >> data. It may or may not be required by the driver. The format
> >> >> of this depends on driver but is the same across architectures.
> >> >>
> >> >> The structure pdev_archdata is a place for architecture specific
> >> >> data. This data is handled by architecture specific code (for
> >> >> example runtime PM), and since it is architecture specific it
> >> >> should _never_ be touched by device driver code. Exactly like
> >> >> struct dev_archdata but for platform devices.
> >> >>
> >> >> Signed-off-by: Magnus Damm <damm@...l.co.jp>
> >> >
> >> > Since there is no 'Feature-desired-by:' tag, I'll addd
> >> >
> >> > Acked-by: Kevin Hilman <khilman@...prootsystems.com>
> >> >
> >> > For PM on ARM in general, and OMAP in particular we definitely need a
> >> > generic way to handle arch-specific data per platform_device.
> >>
> >> Thanks, Kevin! So ARM in general or at least OMAP wants this, and so
> >> does SuperH.
> >>
> >> Rafael, you kindly gave feedback on earlier versions, are you ok with
> >> this version?
> >
> > Yes, I am.  I'm planning to include it into my linux-next branch for 2.6.32, if
> > no one objects.
> 
> Do you have any specific reason for not including this one in 2.6.31?

Basically, it was too late for the merge window.

I think changes of this kind should really go in at the beginning of a merge
window, after spending a few weeks in linux-next so that no one is surprised.

It also needs an ACK from Greg.

> I guess you were thinking of keeping it together with your Runtime PM
> patches targeted for 2.6.32?
> 
> IMO, this patch is decoupled from Runtime PM. It will of course be
> used for Runtime PM on SuperH, but it can for instance also be used
> together with the clock framework.  On top of that, the patch is only
> adding code so it's very unlikely to cause any breakage.
> 
> If possible, I'd like this to be merged as early as possible since a
> lot of processor specific changes will depend on it. With this
> included in 2.6.31 I can easily build arch specific code for 2.6.32.
> Anything I can do to make that happen?
> 
> My top priority is Runtime PM for SuperH on top of your code, and I
> intend to post a prototype for SuperH before the PM Summit. It would
> be great to minimize the dependencies though, and including this in
> 2.6.31 would certainly help.

I'm going to add this patch to my linux-next branch shortly and if your 2.6.32
development is based on that branch (I'd recommend that anyway), there
shouldn't be any problems during the 2.6.32 merge window.

Thanks,
Rafael
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