linux-kernel - Re: [Patch v2 1/2] gpio: add GPIO hogging mechanism

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Date:	Tue, 2 Dec 2014 15:29:46 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Alexandre Courbot <gnurou@...il.com>
Cc:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Benoit Parrot <bparrot@...com>,
	Pantelis Antoniou <panto@...oniou-consulting.com>,
	Jiri Prchal <jiri.prchal@...ignal.cz>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [Patch v2 1/2] gpio: add GPIO hogging mechanism

On Tue, Dec 2, 2014 at 3:13 PM, Alexandre Courbot <gnurou@...il.com> wrote:
> On Tue, Dec 2, 2014 at 1:36 AM, Maxime Ripard
> <maxime.ripard@...e-electrons.com> wrote:

>> The only thing I'd like to have would be that the request here would
>> be non-exclusive, so that a later driver would still be allowed later
>> on to request that GPIO later on and manage it itself (ideally using
>> the usual gpiod_request function).
>
> Actually we have a plan (and I have some code too) to allow multiple
> consumers per GPIO. Although like Benoit I wonder why you would want
> to hog a GPIO and then request it properly later. Also, that probably
> means we should abandon the hog since it actively drives the line and
> would interfere with the late requested. How to do that correctly is
> not really clear to me.

I don't get the usecase. A hogged GPIO is per definition hogged.
This sounds more like "initial settings" or something, which is another
usecase altogether.

Yours,
Linus Walleij
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