From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from az33egw02.freescale.net (az33egw02.freescale.net [192.88.158.103]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "az33egw02.freescale.net", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTP id 2E378DDDCA for ; Thu, 26 Jul 2007 05:06:03 +1000 (EST) Message-ID: <46A79F14.9040409@freescale.com> Date: Wed, 25 Jul 2007 14:05:56 -0500 From: Scott Wood MIME-Version: 1.0 To: Sergei Shtylyov 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 Cc: linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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