linux-kernel - Re: [PATCH 1/2] Documentation/gpio.txt: Explain expected pinctrl interaction

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Message-ID: <20120220073941.GC22562@n2100.arm.linux.org.uk>
Date:	Mon, 20 Feb 2012 07:39:41 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Stephen Warren <swarren@...dia.com>
Cc:	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Olof Johansson <olof@...om.net>,
	Colin Cross <ccross@...roid.com>, linux-doc@...r.kernel.org,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-tegra@...r.kernel.org, Chris Ball <cjb@...top.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] Documentation/gpio.txt: Explain expected pinctrl
	interaction

On Sun, Feb 19, 2012 at 11:27:42PM -0700, Stephen Warren wrote:
> Update gpio.txt based on recent discussions regarding interaction with the
> pinctrl subsystem.
> 
> Previously, gpio_request() was described as explicitly not performing any
> required mux setup operations etc.
> 
> Now, gpio_request() is explicitly as explicitly performing any required mux
> setup operations where possible. In the case it isn't, platform code is
> required to have set up any required muxing or other configuration prior to
> gpio_request() being called, in order to maintain the same semantics.

So what if you need to have the pin as a GPIO, manipulate it as a GPIO,
and then hand it off to a special function, and then take it back as
a GPIO before you shut the special function down ?
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