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From: Paul Mundt <lethal@linux-sh.org>
Subject: Re: [PATCH 6/9] gpiolib: use descriptors internally
Date: Wed, 13 Feb 2013 00:59:28 +0900
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To: Linus Walleij <linus.walleij@linaro.org>
Cc: Stephen Warren <swarren@wwwdotorg.org>, Grant Likely <grant.likely@secretlab.ca>, Alexandre Courbot <acourbot@nvidia.com>, Arnd Bergmann <arnd@arndb.de>, linux-arch <linux-arch@vger.kernel.org>, "linux-arm-kernel@lists.infradead.org" <linux-arm-kernel@lists.infradead.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Alexandre Courbot <gnurou@gmail.com>, Mark Brown <broonie@opensource.wolfsonmicro.com>, Mike Turquette <mturquette@linaro.org>

On Tue, Feb 12, 2013 at 01:29:10PM +0100, Linus Walleij wrote:
> On Mon, Feb 11, 2013 at 6:39 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
> > On 02/11/2013 07:09 AM, Linus Walleij wrote:
> 
> >> However if you take this all the way to the descriptor API
> >> it will make the consumer (driver) API for GPIO descriptors deviate
> >> from what is today used for clocks, regulators and pins.
> >>
> >> With all the resulting confusion for users.
> >> I've seen worse subsystem deviations though.
> >
> > Sorry I haven't looked at the specific APIs this discussion refers to,
> > but clients of the GPIO descriptor API are going to need to distinguish
> > "fail" from "deferred probe", so at least some initial get-like API will
> > need to pass back some error detail...
> 
> Right, so in some other patch I stated that this would lead
> to a GPIO descriptor fetch interface such as this:
> 
> int gpiod_get(struct gpiod_desc **gpiod, struct device *dev, const char *name);
> 
> Rather than the more established:
> 
> struct gpio_desc *gpiod_get(struct device *dev, const char *name);
> 
> And I'm worried about the lack of consistency.
> 
> While I do get the point... I chatted with Grant about it and
> I want to talk to some toolchain people about this to see if
> pointers containing potential error codes can somehow be
> "flagged" by the compiler so we can enforce error checking on
> them. (It may sound a bit utopic...)
> 
At the very least you can __must_check annotate, although that's probably
still a bit coarser grained than what you're after.