linux-kernel - Re: [PATCH 0/2] RFC: gpio: driver-local pin configuration

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Date:	Wed, 29 Jun 2011 09:39:46 +0200
From:	Stijn Devriendt <highguy@...il.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Kyungmin Park <kmpark@...radead.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	Rohit Vaswani <rvaswani@...eaurora.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Russell King <linux@....linux.org.uk>,
	Ben Nizette <bn@...sdigital.com>,
	Lee Jones <lee.jones@...aro.org>,
	H Hartley Sweeten <hartleys@...ionengravers.com>,
	linux-arm-kernel@...ts.infradead.org,
	Kurt Van Dijck <kurt.van.dijck@....be>
Subject: Re: [PATCH 0/2] RFC: gpio: driver-local pin configuration

On Wed, Jun 29, 2011 at 8:18 AM, Linus Walleij <linus.walleij@...aro.org> wrote:
> 2011/6/28 Stijn Devriendt <highguy@...il.com>:
>> On Mon, Jun 27, 2011 at 2:37 PM, Linus Walleij <linus.walleij@...aro.org> wrote:
>>> On Mon, Jun 27, 2011 at 2:02 PM, Mark Brown
>>>> How about device tree usage?  I guess there we'd end up doing it by
>>>> putting the configuration on the GPIO end of things rather than on the
>>>> GPIO user side?
>>>
>>> Sorry I can't quite understand that, please elaborate!
>>>
>>
>> I have some code doing this as well (in a very limited fashion):
>>
>> int of_request_gpio(..., int* remaining_flags)
>> {
>>  of_get_gpio_flags(of_dev, i, remaining_flags)
>>  if (flags & bias_X) {
>>     gpio_set_bias(gpio, ...)
>>     flags &= ~bias_X
>>  }
>>  // interpret all generic flags here
>> };
>>
>> So drivers need not worry about all gpio flags and special things.
>> They just request the pin; what they receive is a fully configured
>> pin (with the exception of unknown flags passed out via
>> remaining_flags).
>
> Sorry there is something I don't get here or there is something you
> assume, maybe.
>
> How does this kind of design account for the case where you need
> to change the biasing at runtime?
>
You're right, it doesn't. It only accounts for preconfiguring pins from
device-tree of platform data.

Regards,
Stijn
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