linux-kernel - Re: [RFC Patch] gpio: add GPIO hogging mechanism

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Message-ID: <CACRpkda-HbKmN_RisHpWRV4bquwpBsd4RgaA5pW0qXrhYChRYA@mail.gmail.com>
Date:	Mon, 3 Nov 2014 10:43:46 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Pantelis Antoniou <pantelis.antoniou@...il.com>
Cc:	Benoit Parrot <bparrot@...com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [RFC Patch] gpio: add GPIO hogging mechanism

On Wed, Oct 29, 2014 at 9:53 AM, Pantelis Antoniou
<pantelis.antoniou@...il.com> wrote:

> 3) I’m not very fond of having this being part of the gpio controller. This
> configuration conceptually has little to do with the gpio controller per se,
> it is more of a board specific thing. Why not come up with a gpio-hog driver that
> references GPIOs? That way with a single gpio-hog driver instance you could setup
> all the GPIO-hogging configuration for all GPIOs on the board, even one that
> lie on different GPIO controllers.

You have a point. But it's vital that we set up hogs at the same time as the
gpio_chip is probed, not later, or there may be a race as to who
gets the GPIO line, and that should be avoided at any cost.

Yours,
Linus Walleij
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