From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linux-foundation.org (smtp1.linux-foundation.org [140.211.169.13]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "smtp.linux-foundation.org", Issuer "CA Cert Signing Authority" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 69818DDFF0 for ; Wed, 28 May 2008 07:59:45 +1000 (EST) Date: Tue, 27 May 2008 14:59:28 -0700 (PDT) From: Linus Torvalds To: Alan Cox Subject: Re: MMIO and gcc re-ordering issue In-Reply-To: <20080527223822.57306677@core> Message-ID: References: <1211852026.3286.36.camel@pasglop> <20080526.184047.88207142.davem@davemloft.net> <1211854540.3286.42.camel@pasglop> <20080526.192812.184590464.davem@davemloft.net> <1211859542.3286.46.camel@pasglop> <1211922621.3286.80.camel@pasglop> <20080527223822.57306677@core> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, tpiepho@freescale.com, linuxppc-dev@ozlabs.org, scottwood@freescale.com, David Miller List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 27 May 2008, Alan Cox wrote: > > > re-ordering, even though I doubt it will be visible in practice. So if you > > use the "__" versions, you'd better have barriers even on x86! > > Are we also going to have __ioread*/__iowrite* ? I doubt there is any reason to. Let's just keep them very strictly ordered. > Also is the sematics of __readl/__writel defined for all architectures - > I used it ages ago in the i2o drivers for speed and it got removed > because it didn't build on some platforms. Agreed - I'm not sure the __ versions are really worth it. We have them, but the semantics are subtle enough that most drivers will never care enough to really use them. I would suggest using them mainly for architecture-specific drivers, on architectures where it actually matters (which is not the case on x86). Linus