From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brownell Subject: Re: [PATCH] Define a NO_GPIO macro to compare against and to use as an invalid GPIO Date: Fri, 8 Feb 2008 15:43:42 -0800 Message-ID: <200802081543.42467.david-b@pacbell.net> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org To: Guennadi Liakhovetski Cc: linux-kernel@vger.kernel.org, i2c@lm-sensors.org List-Id: linux-i2c@vger.kernel.org On Thursday 31 January 2008, Guennadi Liakhovetski wrote: > As discussed on i2c mailing list with David Brownell, and number > outside of the 0...MAX_INT range is invalid as a GPIO number. > Define a macro, similar to NO_IRQ, to be used as a deliberate > invalid GPIO, rather than defining a is_valid_gpio() macro. Actually I thought that what you needed was an is_valid_gpio(); your motivation was that you needed a predicate. The problem I have with a #define for a single such invalid GPIO number is that people will inevitably start to assume it's the only such number. In particular "if (gpio == NO_GPIO) ..." is by definition incorrect. So I'd really rather see a predicate like is_valid_gpio(). If you want to designate one value for use as an initializer, then I'd rather see a simple #define NO_GPIO (-EINVAL) without any option for arch-specific overrides ... along with a comment that this is only *one* of the numerous values which will fail is_valid_gpio(). - Dave > > Signed-off-by: Guennadi Liakhovetski > > --- > > As gpiolib doesn't seem to have an own mailing list, sending it directly > to LKML. > > include/asm-generic/gpio.h | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h > index f29a502..806b86c 100644 > --- a/include/asm-generic/gpio.h > +++ b/include/asm-generic/gpio.h > @@ -16,6 +16,10 @@ > #define ARCH_NR_GPIOS 256 > #endif > > +#ifndef NO_GPIO > +#define NO_GPIO ((unsigned int)-1) > +#endif > + > struct seq_file; > > /** > -- > 1.5.3.4 >