linux-kernel - Re: [PATCH] gpio: add support for ITE IT87xx Super I/O GPIO.

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Date:	Mon, 19 Mar 2012 09:26:44 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Guenter Roeck <guenter.roeck@...csson.com>
Cc:	Diego Elio Pettenò <flameeyes@...meeyes.eu>,
	Grant Likely <grant.likely@...retlab.ca>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Denis Turischev <denis@...pulab.co.il>
Subject: Re: [PATCH] gpio: add support for ITE IT87xx Super I/O GPIO.

On Mon, Mar 19, 2012 at 1:54 AM, Guenter Roeck
<guenter.roeck@...csson.com> wrote:
> On Sun, Mar 18, 2012 at 07:14:45PM -0400, Linus Walleij wrote:
>> On Sat, Mar 17, 2012 at 7:53 PM, Diego Elio Pettenņ
>> <flameeyes@...meeyes.eu> wrote:
>>
>> > Another reason to have a MFD driver would be to allow tweaking the few
>> > more knobs that (at least IT8728F) expose, such as the ability to switch
>> > a few pre-defined inputs and outputs to GPIO instead, and so on...
>>
>> Hm that sounds an awful lot like pin multiplexing. Is that the case?
>>
> Depending on the chip configuration, a physical pin may be a GPIO pin, or a UART pin,
> or a fan control pin, or a FD pin, or something else. This does not apply to all pins,
> but to many of the GPIO pins.

OK that is pinmuxing, if that is to be software-controlled the place to do
it is in drivers/pinctrl. (Documentation/pinctrl.txt gives the backrgound.)

The rule is in that case to put the driver below drivers/pinctrl/* and also
expose a gpiolib interface from that driver.

As we convert drivers to the new pinctrl interfaces we tend to move them
from drivers/gpio to drivers/pinctrl. But no biggie, if pinctrl is added later,
it can be moved by then. I'm mainly concerned with blocking any
extra custom interfaces to the gpio drivers.

Yours,
Linus Walleij
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