linux-kernel - Re: [PATCH] GPIOLIB: add generic gpio_set

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Message-ID: <CACRpkdZE45cSUTKBfJ=sqmw35MG1f_2s=Jyh350QXpATT_wFxQ@mail.gmail.com>
Date:	Thu, 21 Jun 2012 09:48:59 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Paul Mundt <lethal@...ux-sh.org>
Cc:	Barry Song <21cnbao@...il.com>,
	Rohit Vaswani <rvaswani@...eaurora.org>,
	Kyungmin Park <kmpark@...radead.org>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org, workgroup.linux@....com,
	Grant Likely <grant.likely@...retlab.ca>,
	Richard Woo <richard.wu@...nlab.org>,
	linux-arm-kernel@...ts.infradead.org,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: [PATCH] GPIOLIB: add generic gpio_set_pull API

On Wed, Jun 20, 2012 at 4:31 PM, Paul Mundt <lethal@...ux-sh.org> wrote:
> On Wed, Jun 20, 2012 at 10:15:01AM +0200, Linus Walleij wrote:
>> On Tue, Jun 19, 2012 at 5:25 AM, Barry Song <21cnbao@...il.com> wrote:
>> > but i think at least the macros of GPIO_PULL_NONE, GPIO_PULL_UP and
>> > GPIO_PULL_DOWN should be standardized.
>>
>> You find an attempt at standardization in drivers/pinctrl/pinconf-generic.c
>> which is also used by the composite U300+COH901 drivers. Drivers
>> can select this support library and use the flags from
>> <linux/pinctrl/pinconf-generic.h>
>>
> What's with PIN_CONFIG_END using such an insane value?

This: PIN_CONFIG_END = 0x7FFF

It's just that I reserved 16 bits for the different stuff, and then
the bitstuffing
functions below use 16 bits for this. If it's too much we can shrink
it.

> I'm happy to consolidate on the provided definitions and add my own on top
> of that, but I'm not going to waste an insane amount of bits that I could
> be using for driver-specific data and so on instead to comply with the
> PIN_CONFIG_END comment. Is there any valid reason why this would ever
> need to exceed 4 bits?

I think we need more than 4 bits for sure, but not more than 8.

If you want to patch it down to have 8 bits for the param and 24 bits
for the argument, go ahead, it won't hurt.

Yours,
Linus Walleij
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