From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763488AbXGYTGU (ORCPT ); Wed, 25 Jul 2007 15:06:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754018AbXGYTGJ (ORCPT ); Wed, 25 Jul 2007 15:06:09 -0400 Received: from az33egw02.freescale.net ([192.88.158.103]:47434 "EHLO az33egw02.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752692AbXGYTGH (ORCPT ); Wed, 25 Jul 2007 15:06:07 -0400 Message-ID: <46A79F14.9040409@freescale.com> Date: Wed, 25 Jul 2007 14:05:56 -0500 From: Scott Wood User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.7.10) Gecko/20050909 Red Hat/1.7.10-1.1.3.2 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Sergei Shtylyov CC: Vitaly Bordug , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org Subject: Re: [PATCH 1/2] [IDE] Platform IDE driver (was: MMIO IDE driver) References: <20070725165318.5331.23795.stgit@localhost.localdomain> <46A79DE0.8060405@ru.mvista.com> In-Reply-To: <46A79DE0.8060405@ru.mvista.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Sergei Shtylyov wrote: >>+ hwif->hw.io_ports[IDE_DATA_OFFSET] = port; >>+ >>+ port += (1 << pdata->ioport_shift); >>+ for (i = IDE_ERROR_OFFSET; i <= IDE_STATUS_OFFSET; >>+ i++, port += (1 << pdata->ioport_shift)) > > > Looks like shift doesn't buy as anything, why not just use stride? It doesn't buy us anything in here, but it's conceivable that someone may want to write a driver that uses a shift in the I/O accessor rather than an array of port offsets, and it's easier to convert a shift to a stride than the other way around (not all architectures have an equivalent of the cntlzw innstruction, and shift makes it clear that the stride must be power-of-two). Plus, using shift is consistent with what we do on ns16550. -Scott