Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:43687 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751101AbXIRVav (ORCPT ); Tue, 18 Sep 2007 17:30:51 -0400 Message-ID: <46F04386.8010209@garzik.org> Date: Tue, 18 Sep 2007 17:30:46 -0400 From: Jeff Garzik MIME-Version: 1.0 To: Linus Torvalds CC: "Luis R. Rodriguez" , Alan Cox , linux-kernel , "John W. Linville" , linux-wireless Subject: Re: [PATCH] Clarify pci_iomap() usage for MMIO-only devices References: <43e72e890709171322x76ab6b70xd29bf97e3643c553@mail.gmail.com> <20070918113401.6a8a737f@the-village.bc.nu> <43e72e890709181146s604e0f9fl8b0c16627469c77f@mail.gmail.com> <43e72e890709181207j7c85dc29sb355a9f5a4207411@mail.gmail.com> <43e72e890709181312sf2b421cn49be3389b3786a2a@mail.gmail.com> <43e72e890709181402x7335d0acp306cf576fac6c070@mail.gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: Linus Torvalds wrote: > The old situation with SATA drivers that had > > if (iomem) > writel(..) > else > outl(..) > > in the cases that needed it (and used hardcoded writel/outl in the cases > that didn't) was an example of code that "in theory" is faster. But > dammit, in practice that mattered not one whit, and what iomap() tries to > do is to attack the _real_ problem we had in that area. > > Which had nothing what-so-ever to do with any branches. And none of those issues are a factor at all in ath5k (which spawned this sub-discussion), or indeed many other drivers. The above code you cite is -generic-, hardware agnostic code. Most new hardware is MMIO-only, making ioread32() only for drivers that care about legacy IO support, something that is being slowly phased out. e.g. legacy IDE, legacy 10/100 mbps ethernet NICs with the dual MMIO/PIO register spaces. Jeff