From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [PATCH] ata: Don't use NO_IRQ in pata_of_platform driver Date: Tue, 6 Dec 2011 21:59:55 +0100 Message-ID: <20111206205955.GH4585@pengutronix.de> References: <1322867573.11728.22.camel@pasglop> <20111205161157.GA27550@localhost.localdomain> <20111205180253.GB29812@localhost.localdomain> <20111205192605.GD29812@localhost.localdomain> <20111206093709.GB2274@linaro.org> <20111206104654.GN14542@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Linus Torvalds Cc: Nicolas Pitre , Stephen Rothwell , Russell King - ARM Linux , Pawel Moll , devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Ingo Molnar , LKML , linux-ide-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Randy Dunlap , linux-next-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alan Cox , Anton Vorontsov , Andrew Morton , Jeff Garzik , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-ide@vger.kernel.org Hello Linus, On Tue, Dec 06, 2011 at 11:20:49AM -0800, Linus Torvalds wrote: > On Tue, Dec 6, 2011 at 2:46 AM, Russell King - ARM Linux > wrote: > > > > But.. let's make one thing clear: Alan Cox and Linus have been going on > > about how IRQ0 should not be used. =A0Let's be crystal clear: even x86 > > uses IRQ0. > = > Not for any device driver, though. > = > It's used entirely internally, and it doesn't even use > "request_irq()". It uses the magic internal "setup_irq()" and never > *ever* exposes irq0 as anything that a driver can see. > = > That's what matters. You can use irq0 in ARM land all you like, AS > LONG AS IT'S SOME HIDDEN INTERNAL USE. No drivers. No *nothing* that > ever uses that absolutely *idiotic* NO_IRQ crap. > = > In fact, you may be *forced* to use what is "physically" irq0 - it's > just that you should never expose it as such to drivers. And x86 > doesn't. > = > So Russell, if you think this has anything to do with NO_IRQ, and how > x86 isn't doing things right, you're wrong. It's just like the > internal exception thing, or the magical "cascade interrupt", or the > "x87 exception mapped through the PIC". They are magic hidden > interrupts that are set up in one place (well, one place *each*), and > are never exposed anywhere else. Well there is try_misrouted_irq in kernel/irq/spurious.c that assumes irq0 to be something that it never is on ARM (and maybe all other platforms apart from x86). So at least it's not internal to a single (x86 specific) place. I tried to patch that two years ago, but that only ended in people saying "don't use irq0". I don't know if try_misrouted_irq sees hardware irqs, but if it does it's a bug even on archs !=3D X86 that use virtual irqs. (Note that this doesn't oppose to your statement that using NO_IRQ is crap.) > The problem with NO_IRQ is that stupid "we expose our mind-numbingly > stupid interfaces across the whole kernel". > = > x86 never did that. ARM still does. x86 doesn't have to fix anything. AR= M does. Best regards Uwe -- = Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | http://www.pengutronix.de/ |