linux-kernel - Re: [PATCH V2 1/3] drivers/pwm st_pwm: Add support for ST's Pulse Width Modulator

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Message-ID: <4DEDF909.2000608@st.com>
Date:	Tue, 7 Jun 2011 15:40:17 +0530
From:	viresh kumar <viresh.kumar@...com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Arnd Bergmann <arnd@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Armando VISCONTI <armando.visconti@...com>,
	Shiraz HASHIM <shiraz.hashim@...com>,
	Vipin KUMAR <vipin.kumar@...com>,
	Rajeev KUMAR <rajeev-dlh.kumar@...com>,
	Deepak SIKRI <deepak.sikri@...com>,
	Vipul Kumar SAMAR <vipulkumar.samar@...com>,
	Amit VIRDI <Amit.VIRDI@...com>,
	Pratyush ANAND <pratyush.anand@...com>,
	Bhupesh SHARMA <bhupesh.sharma@...com>,
	"viresh.linux@...il.com" <viresh.linux@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 1/3] drivers/pwm st_pwm: Add support for ST's Pulse
 Width Modulator

On 06/07/2011 12:58 PM, Arnd Bergmann wrote:
> On Tuesday 07 June 2011 05:55:25 viresh kumar wrote:
>>>> +static int __devinit st_pwm_probe(struct platform_device *pdev)
>>>
>>> And here things get rather odd.
>>>
>>> Most of this file is a generic, non-device specific PWM layer, exported
>>> to other modules.  But then we get into driver bits which are specific
>>> to one paritular type of device.  Confused - this is like putting the
>>> e100 driver inside net/ipv4/tcp.c?
>>>
>>
>> Sorry but i couldn't get this one completely. :(
>> Driver is specific to pwm peripheral by ST. This driver can be used for
>> SPEAr or may be other SoC or Devices, and is not at all dependent on SPEAr.
> 
> 

Now i get the question correctly. :)

> It was my suggestion to start drivers/pwm/ with this driver. We currently
> have a number of pwm drivers spread over the entire tree, all using slight
> the same interface header. They all look like this one, and are each used
> on one SOC, so you have to choose at compile-time which one to use.
> 
> There are two problems with this of course:
> 1. the drivers that export the same interface should be in one directory
> 2. there should be a common abstraction layer to avoid duplicate code and
>    enable building a kernel with multiple PWM drivers builtin.
> 
> Moving this driver to drivers/pwm is the first step to address the
> problem 1, we will move the other drivers in the 3.1 or 3.2 timeframe.
> 
> There is independent by Sascha Hauer to work on the abstraction layer
> for all the drivers. Once that is in, we will change the individual drivers
> in drivers/pwm accordingly.
> 

Above was exactly the reason why i didn't separated framework from device
specific part. As soon as framework is pushed, i will update my driver to
work with it.

-- 
viresh
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