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

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Date:	Tue, 28 Sep 2010 16:35:01 +0300
From:	Felipe Balbi <balbi@...com>
To:	Samuel Ortiz <sameo@...ux.intel.com>
Cc:	"V, Hemanth" <hemanthv@...com>,
	Arun Murthy <arun.murthy@...ricsson.com>,
	"lars@...afoo.de" <lars@...afoo.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"philipp.zabel@...il.com" <philipp.zabel@...il.com>,
	"robert.jarzmik@...e.fr" <robert.jarzmik@...e.fr>,
	"marek.vasut@...il.com" <marek.vasut@...il.com>,
	"eric.y.miao@...il.com" <eric.y.miao@...il.com>,
	"rpurdie@...ys.net" <rpurdie@...ys.net>,
	"kgene.kim@...sung.com" <kgene.kim@...sung.com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
	"STEricsson_nomadik_linux@...t.st.com" 
	<STEricsson_nomadik_linux@...t.st.com>
Subject: Re: [PATCH 1/7] pwm: Add pwm core driver

On Tue, Sep 28, 2010 at 08:06:11AM -0500, Samuel Ortiz wrote:
>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.

FWIW, I agree with you Sam. Sooner or later, this will hit other SoCs.

-- 
balbi
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