linux-kernel - Re: [PATCH 4/5] gpiolib: handle deferral probe error

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Date:	Fri, 7 Oct 2011 16:09:38 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	"G, Manjunath Kondaiah" <manjugk@...com>,
	Dilan Lee <dilee@...dia.com>, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <greg@...ah.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Manjunath GKondaiah <manjunath.gkondaiah@...aro.org>,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/5] gpiolib: handle deferral probe error

On Fri, Oct 7, 2011 at 4:06 AM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> On Fri, 07 Oct 2011 10:33:09 +0500
> "G, Manjunath Kondaiah" <manjugk@...com> wrote:
>
>>
>> The gpio library should return -EPROBE_DEFER in gpio_request
>> if gpio driver is not ready.
>
> Why not use the perfectly good existing error codes we have for this ?
>
> We have EAGAIN and EUNATCH both of which look sensible.

I want a distinct error code for probe deferral so that a) it doesn't
overlap with something a driver is already doing, and b) so that all
the users can be found again at a later date.

That said, I'm not in agreement with this patch.  It is fine for gpio
lib to have a code that means the pin doesn't exist (yet), but the
device driver needs to be the one to decide whether or not it is
appropriate to use probe deferral.

g.
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