From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [PATCH 6/7] spi/mpc8xxx: don't check platform_get_irq's return value against zero Date: Wed, 16 Dec 2009 18:49:04 +0100 Message-ID: <20091216174904.GB26325@pengutronix.de> References: <1260979809-24811-1-git-send-email-u.kleine-koenig@pengutronix.de> <1260979809-24811-2-git-send-email-u.kleine-koenig@pengutronix.de> <1260979809-24811-3-git-send-email-u.kleine-koenig@pengutronix.de> <1260979809-24811-4-git-send-email-u.kleine-koenig@pengutronix.de> <1260979809-24811-5-git-send-email-u.kleine-koenig@pengutronix.de> <1260979809-24811-6-git-send-email-u.kleine-koenig@pengutronix.de> <20091216163229.GA26350@oksana.dev.rtsoft.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-kernel@vger.kernel.org, David Vrabel , Greg Kroah-Hartman , David Brownell , Grant Likely , Kumar Gala , Andrew Morton , spi-devel-general@lists.sourceforge.net, Linus Torvalds To: Anton Vorontsov Return-path: Content-Disposition: inline In-Reply-To: <20091216163229.GA26350@oksana.dev.rtsoft.ru> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org Hello, [Note the email address used for David Vrabel isn't valid any more, this mail uses his last used address.] On Wed, Dec 16, 2009 at 07:32:29PM +0300, Anton Vorontsov wrote: > On Wed, Dec 16, 2009 at 05:10:08PM +0100, Uwe Kleine-K=F6nig wrote: > > platform_get_irq returns -ENXIO on failure, so !irq was probably > > always true. Better use (int)irq <=3D 0. Note that a return value= of > > zero is still handled as error even though this could mean irq0. > >=20 > > This is a followup to 305b3228f9ff4d59f49e6d34a7034d44ee8ce2f0 that > > changed the return value of platform_get_irq from 0 to -ENXIO on er= ror. > >=20 > > Signed-off-by: Uwe Kleine-K=F6nig > > --- >=20 > Noooooo... :-( >=20 > Please revert 305b3228f9ff4d59f49e6d34a7034d44ee8ce2f0 instead, > and fix platforms to remap HWIRQ0 to something that is not VIRQ0. >=20 > IRQ0 is invalid for everything that is outside of arch/*. >=20 > http://lkml.org/lkml/2005/11/22/159 > http://lkml.org/lkml/2005/11/22/213 > http://lkml.org/lkml/2005/11/22/227 =46irst note that my check is safe with both variants (e.g. it does the right thing independent of the error being signaled by 0 or -ESOMETHING.) Then arch/arm/mach-pxa/devices.c has: static struct resource pxa27x_resource_ssp3[] =3D { ... [1] =3D { .start =3D IRQ_SSP3, .end =3D IRQ_SSP3, .flags =3D IORESOURCE_IRQ, }, ... } with IRQ_SSP3 being zero (sometimes). The driver is implemented in arch/arm/mach-pxa/ssp.c and uses platform_get_irq. So according to you= r definition it's allowed (arch/* only). Still this would break if you revert 305b3228f9. Actually I don't care much, but as platform_get_irq returns an int I think it's fine for it to signal an error using a value < 0 as irqs are not negative. My position regarding irq0 is: If a variable holds either a valid irq or a value indicating "no irq", then feel free to use 0 as "no irq" and a value > 0 for a valid irq (without offset). If you want irq0 here, you're out of luck. But if you have a variable holding a valid irq onl= y (that is, there is no doubt if the value is valid or not) I see no reason to dogmatically prohibit irq0. I'm a bit annoyed as this is the third time[1] this month this irq0 discussion pops up for me. I think people see that irq0 is involved somehow, start wailing and stop seeing the issues being fixed. Best regards Uwe [1] one is: http://thread.gmane.org/gmane.linux.kernel/924739 the other wasn't on lkml, only mm-commits. Cannot find it on the net now. --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig = | Industrial Linux Solutions | http://www.pengutronix.= de/ |