linux-kernel - Re: [PATCH 1/6] gpiolib: Allow GPIO chips to request their own GPIOs

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Date:	Wed, 5 Mar 2014 10:49:41 +0800
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Alexandre Courbot <acourbot@...dia.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Lan Tianyu <tianyu.lan@...el.com>,
	Lv Zheng <lv.zheng@...el.com>, Alan Cox <alan.cox@...el.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/6] gpiolib: Allow GPIO chips to request their own GPIOs

On Tue, Feb 25, 2014 at 12:00 AM, Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:

> Sometimes it is useful to allow GPIO chips themselves to request GPIOs they
> own through gpiolib API. One usecase is ACPI ASL code that should be able
> to toggle GPIOs through GPIO operation regions.
>
> We can't really use gpio_request() and its counterparts because it will pin
> the module to the kernel forever (as it calls module_get()). Instead we
> provide a gpiolib internal functions gpiochip_request/free_own_desc() that
> work the same as gpio_request() but don't manipulate module refrence count.
>
> Since it's the GPIO chip driver who requests the GPIOs in the first place
> we can be sure that it cannot be unloaded without the driver knowing about
> that. Furthermore we only limit this functionality to be available only
> inside gpiolib.
>
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>

I fully trust you in doing the ACPI stuff in patches 2-n but on this patch
in particular I want Alexandre's review tag as well, as he's working
actively with the descriptor API and I don't want to add too many quirks
without his consent.

So Alexandre, what do you say about this?

Yours,
Linus Walleij
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