linux-kernel - pinctrl discussions @ Linaro Connect, and also requesting GPIOs

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Date:	Wed, 9 Nov 2011 12:34:27 -0800
From:	Stephen Warren <swarren@...dia.com>
To:	"Linus Walleij (linus.walleij@...aro.org)" <linus.walleij@...aro.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: pinctrl discussions @ Linaro Connect, and also requesting GPIOs

Linus,

I'm curious about any pinctrl-related discussions that happened at Linaro
Connect. Are you able to summarize any discussions/decisions, or point me
at some existing summary? Especially anything to do with the new pin config
options, possibly extending the mapping table to control them, etc.

On the topic of pinctrl:

Many drivers currently call gpio_request(). This is defined /not/ to
perform any pinmux manipulation. On Tegra, the pinmux is set up due to
board files calling tegra_gpio_enable() before probing drivers. I'm
wondering:

a) Should drivers explicitly call pinmux_request_gpio() before calling
gpio_request() instead, so that the board files don't have to set this up
first?

b) Shouldn't this be hidden inside the pinctrl's mapping table; if a driver
needs to set up non-GPIO pinmux options, it's all done in pinmux_get() and
pinmux_enable(), whereas for GPIOs they need to use the other API. Can we
unify this?

I think extending the mapping table to be able to represent either the
existing mux configuration, or GPIO allocation, might make sense. In fact,
if we do that, perhaps pinmux_{request,free}_gpio() wouldn't even be needed?

What are your thoughts?

-- 
nvpublic

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