linux-kernel - Re: [RFC PATCH v3 0/2] drivers: mfd: Versatile Express SPC support

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Message-ID: <1371547782.16725.11.camel@hornet>
Date:	Tue, 18 Jun 2013 10:29:42 +0100
From:	Pawel Moll <pawel.moll@....com>
To:	Samuel Ortiz <sameo@...ux.intel.com>
Cc:	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	Jon Medhurst <tixy@...aro.org>,
	Achin Gupta <Achin.Gupta@....com>,
	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [RFC PATCH v3 0/2] drivers: mfd: Versatile Express SPC support

Morning, Samuel,

On Tue, 2013-06-18 at 10:09 +0100, Samuel Ortiz wrote:
> Hi Pawell,

Double l in the wrong place ;-)

> > If you feel strongly about it, I'm ready to split it into mfd_cells and
> > move the gpio and leds code into separate drivers, however I'm not
> > convinced that it's worth the effort.
> Well, after seeing your last patch for ifdef'ing the GPIO and LED code,
> I think it is worth the effort.

Good point. But as this - obviously - won't happen on time for 3.11, I
hope you would be kind enough to take the #ifdef patch in for now.

> > Now, as to the vexpress-config.c... The first time I've posted the
> > series, all parts lived in "driver/misc(/vexpress)", but (if I remember
> > correctly) Arnd had some feelings about "misc" existence at all... I was
> > thinking about a separate directory for random "system/platform/machine
> > configuration" drivers, but the idea didn't get any traction.
> drivers/misc would already have been a nicer option imo.

Ok. Quite conveniently Arnd is the driver/misc maintainer so I'll get
first-hand feedback on this.

> > > Not only that, but the whole vexpress-config code design is not the
> > > nicest piece of code I've ever seen. And I'm usually not picky. e.g. the
> > > whole vexpress-config ad-hoc API is awkward and I wonder if it could be
> > > implemented as a bus instead.
> > 
> > Funny you mention this :-) Again, the first version actually was a
> > vexpress-config bus. The feedback was - a whole bus_type is over the top
> > (I'm simplifying the letter slightly but this was the spirit).
> I think it would make sense to have it under drivers/bus/. It might be a
> little over the top, but when I look at the current code I'd be really
> happy to read an over-the-top bus driver instead. At least we'd know
> straight away what youre trying to achieve with this code and it would
> probably remove a fair chunk of the weird bridge API (the registering
> and the function reference stuff).
> Do you have a reference for the patch first version ?

http://thread.gmane.org/gmane.linux.ports.arm.kernel/185014/focus=185019

> > So to summarize - I'm open to any suggestions and ready to spend time on
> > this stuff.
> I'd say splitting the sysreg driver and leaving only the MFD bits in the
> MFD driver would be a first step.
> Also, re-considering the bus implementation for the config part would
> also be interesting. 

Ok, so what I'll do:

1. Split vexpress-sysreg into
* gpio driver
* leds driver
* the rest (still in mfd though)

2. Move the vexpress-sysreg "platform management" functions into misc
(unless we get any better place for it)

3. Move vexpress-config into drivers/bus as it is (however I see no one
in MAINTAINERS for this directory)

4. *Try* to use more of the standard bus (aka bus_type) infrastructure,
however this will be the trickiest part of this all - as I've mentioned
the code must be functional before SLAB is up...

You shall see some patches before 3.11-rc1.

Paweł


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