linux-kernel - Re: [PATCH] regulator: core: GPIO #0 is a valid GPIO

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Date:	Mon, 1 Sep 2014 13:06:02 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Dmitry Eremin-Solenikov <dmitry_eremin@...tor.com>
Cc:	Dirk Behme <dirk.behme@...bosch.com>, linux-kernel@...r.kernel.org,
	Liam Girdwood <lgirdwood@...il.com>,
	Gokulkrishnan Nagarajan <Gokulkrishnan.Nagarajan@...bosch.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] regulator: core: GPIO #0 is a valid GPIO

On Mon, Sep 01, 2014 at 03:59:34PM +0400, Dmitry Eremin-Solenikov wrote:
> On 09/01/2014 02:15 PM, Mark Brown wrote:

> >There's no practical way to deploy that without breaking users - as soon
> >as you treat 0 as a valid GPIO you make all existing users relying on
> >the natural behaviour of treating 0 as default instantly buggy which is
> >not practical.  Really the GPIO API is badly specified here.

> Back in the time before DTS conversion started, the 0 was a correct GPIO
> number. If somebody wanted to specify that no gpio is provided, he provided
> -1 as an invalid number. I have the feeling that allowing users to use 0 as
> 'no gpio' is a mistake. Or the API should be changed
> to disallow GPIO 0 to exist at all.

Please consider my point about making users instantly buggy - it's not
practical to introduce a new field into existing platform data which
needs initialization.  Disallowing the use of 0 as a GPIO seems more
practical here (in that it's something the platform can control with
more reliable coordination).

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