linux-kernel - Re: [PATCH 1/7] pwm: Add pwm core driver

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Date:	Tue, 28 Sep 2010 15:06:11 +0200
From:	Samuel Ortiz <sameo@...ux.intel.com>
To:	Hemanth V <hemanthv@...com>
Cc:	Arun Murthy <arun.murthy@...ricsson.com>, lars@...afoo.de,
	Andrew Morton <akpm@...ux-foundation.org>,
	kernel@...gutronix.de, philipp.zabel@...il.com,
	robert.jarzmik@...e.fr, marek.vasut@...il.com,
	eric.y.miao@...il.com, rpurdie@...ys.net, kgene.kim@...sung.com,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
	STEricsson_nomadik_linux@...t.st.com
Subject: Re: [PATCH 1/7] pwm: Add pwm core driver

On Tue, Sep 28, 2010 at 06:23:24PM +0530, Hemanth V wrote:
> ----- Original Message ----- From: "Arun Murthy"
> <arun.murthy@...ricsson.com>
> 
> 
> >The existing pwm based led and backlight driver makes use of the
> >pwm(include/linux/pwm.h). So all the board specific pwm drivers will
> >be exposing the same set of function name as in include/linux/pwm.h.
> >As a result build fails in case of multi soc environments where each soc
> >has a pwm device in it.
> 
> This seems very specific to ST environment,  
No it's not. It's an issue Arun has hit while enabling one of the ST MFD chip,
but he's tackling a generic issue.

> looking at the driver list from
> ( [PATCH 4/7] pwm: Align existing pwm drivers with pwm-core ) it seems
> most multi SOC environments might support PWM in either one of the SOC.
> 
> arch/arm/plat-mxc/pwm.c
> arch/arm/plat-pxa/pwm.c
> arch/arm/plat-samsung/pwm.c
> arch/mips/jz4740/pwm.c
> drivers/mfd/twl6030-pwm.c
> 
> Unless people have examples of other SOCs which might use this,
> the better approach might be to go for a custom driver rather than changing
> the framework.
I wouldn't call the current pwm code a framework. It's a bunch of header
definitions that happens to work in the specific case of 1 pwm per
sub architecture.
What Arun is proposing is an actual framework. And it seems to be clean and
simple enough.

Cheers,
Samuel.

-- 
Intel Open Source Technology Centre
http://oss.intel.com/
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