From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v3 00/17] Cross-architecture definitions of relaxed MMIO accessors Date: Thu, 25 Sep 2014 21:17:19 +0200 Message-ID: <201409252117.19754.arnd@arndb.de> References: <1411579056-16966-1-git-send-email-will.deacon@arm.com> <4240583.SJ4jiIW6Zy@wuerfel> <54243395.902@linaro.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: Received: from mout.kundenserver.de ([212.227.126.130]:56066 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751755AbaIYTTv (ORCPT ); Thu, 25 Sep 2014 15:19:51 -0400 In-Reply-To: <54243395.902@linaro.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Daniel Thompson Cc: Will Deacon , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "benh@kernel.crashing.org" , "chris@zankel.net" , "cmetcalf@tilera.com" , "davem@davemloft.net" , "deller@gmx.de" , "dhowells@redhat.com" , "geert@linux-m68k.org" , "heiko.carstens@de.ibm.com" , "hpa@zytor.com" , "jcmvbkbc@gmail.com" , "jesper.nilsson@axis.com" , "mingo@redhat.com" , "monstr@monstr.eu" , "paulmck@linux.vnet.ibm.com" , "rdunlap@infradead.org" , "sam@ravnborg.org" On Thursday 25 September 2014, Daniel Thompson wrote: > > + > > +#ifndef readq_relaxed > > +#define readq_relaxed readq > > +#endif > > Not really sure if it matters but this gives a rather surprising > behaviour to #ifdef readq_relaxed given that readq may not be defined. > It was intentional. I could have written this as #if !defined(readq_relaxed) && defined(readq) but the effect would be almost the same, and the version I picked looks simpler. Note that 32-bit architectures could provide readq, it's just the generic code that doesn't, because most you typically don't get atomic 64-bit accesses from dereferencing a 64-bit pointer as the generic readq() function does. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mout.kundenserver.de ([212.227.126.130]:56066 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751755AbaIYTTv (ORCPT ); Thu, 25 Sep 2014 15:19:51 -0400 From: Arnd Bergmann Subject: Re: [PATCH v3 00/17] Cross-architecture definitions of relaxed MMIO accessors Date: Thu, 25 Sep 2014 21:17:19 +0200 References: <1411579056-16966-1-git-send-email-will.deacon@arm.com> <4240583.SJ4jiIW6Zy@wuerfel> <54243395.902@linaro.org> In-Reply-To: <54243395.902@linaro.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Message-ID: <201409252117.19754.arnd@arndb.de> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Daniel Thompson Cc: Will Deacon , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "benh@kernel.crashing.org" , "chris@zankel.net" , "cmetcalf@tilera.com" , "davem@davemloft.net" , "deller@gmx.de" , "dhowells@redhat.com" , "geert@linux-m68k.org" , "heiko.carstens@de.ibm.com" , "hpa@zytor.com" , "jcmvbkbc@gmail.com" , "jesper.nilsson@axis.com" , "mingo@redhat.com" , "monstr@monstr.eu" , "paulmck@linux.vnet.ibm.com" , "rdunlap@infradead.org" , "sam@ravnborg.org" , "schwidefsky@de.ibm.com" , "starvik@axis.com" , "takata@linux-m32r.org" , "tglx@linutronix.de" , "tony.luck@intel.com" , "broonie@linaro.org" , "linux@arm.linux.org.uk" , "thierry.reding@gmail.com" Message-ID: <20140925191719.ASK2nF9QmD7cSabk9g4pt-YUA5euh-3kpb3nkEI1eHs@z> On Thursday 25 September 2014, Daniel Thompson wrote: > > + > > +#ifndef readq_relaxed > > +#define readq_relaxed readq > > +#endif > > Not really sure if it matters but this gives a rather surprising > behaviour to #ifdef readq_relaxed given that readq may not be defined. > It was intentional. I could have written this as #if !defined(readq_relaxed) && defined(readq) but the effect would be almost the same, and the version I picked looks simpler. Note that 32-bit architectures could provide readq, it's just the generic code that doesn't, because most you typically don't get atomic 64-bit accesses from dereferencing a 64-bit pointer as the generic readq() function does. Arnd