linux-kernel - Re: [PATCH 1/3] PWM: add pwm framework support

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Message-ID: <BANLkTin4Sbz=c7V9gu4Qfm3OzZCCpGxOjQ@mail.gmail.com>
Date:	Thu, 30 Jun 2011 20:55:33 -0400
From:	Mike Frysinger <vapier.adi@...il.com>
To:	H Hartley Sweeten <hartleys@...ionengravers.com>
Cc:	Ryan Mallon <rmallon@...il.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Bill Gatliff <bgat@...lgatliff.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ryan Mallon <ryan@...ewatersys.com>,
	Shawn Guo <shawn.guo@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH 1/3] PWM: add pwm framework support

On Thu, Jun 30, 2011 at 20:33, H Hartley Sweeten wrote:
> On Thursday, June 30, 2011 4:24 PM, Ryan Mallon wrote:
>> On 01/07/11 03:02, Sascha Hauer wrote:
>>> I think that you made the fundamental mistake to completly ignore the
>>> existing pwm API and its users. With a competing api we are basically
>>> stuck. We can't convert the existing hardware drivers to the new API
>>> because leds-pwm.c, pwm_bl.c and others still depend on the old API and
>>> boards using it would break.
>>
>> I don't think this is really a blocker to Bill's patches. There are
>> three (that I can see) pwm users currently:
>> drivers/video/backlight/pwm_bl.c
>> drivers/leds/leds-pwm.c
>> drivers/input/misc/pwm-beeper.c
>>
>> All of those drivers are trivial and good easily be updated to work with
>> Bill's patches. Bill already provided a leds-pwm driver.
>
> I agree with Ryan.  The three drivers listed above appear to be the only
> pwm "user" drivers.  They are all trivial and could be updated easily.

indeed ... the current pwm API is almost toy like in its simplicity.

> The "core" drivers using the existing API appear to be:
> arch/blackfin/kernel/pwm.c

i only wrote this because Bill's subsystem wasnt yet merged.  but i
made sure that it was done in such a way that it's trivial to convert
over to Bill's work once it's done.
-mike
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