From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267882AbUGaAyy (ORCPT ); Fri, 30 Jul 2004 20:54:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267889AbUGaAyy (ORCPT ); Fri, 30 Jul 2004 20:54:54 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:5353 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S267882AbUGaAyv (ORCPT ); Fri, 30 Jul 2004 20:54:51 -0400 Message-ID: <410AEDC8.6030901@pobox.com> Date: Fri, 30 Jul 2004 20:54:32 -0400 From: Jeff Garzik User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040510 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Alan Cox CC: Todd Poynor , Bartlomiej Zolnierkiewicz , Linux Kernel Mailing List , tim.bird@am.sony.com, dsingleton@mvista.com Subject: Re: [PATCH] Configure IDE probe delays References: <20040730191100.GA22201@slurryseal.ddns.mvista.com> <1091226922.5083.13.camel@localhost.localdomain> In-Reply-To: <1091226922.5083.13.camel@localhost.localdomain> 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 Alan Cox wrote: > On Gwe, 2004-07-30 at 20:11, Todd Poynor wrote: > >>IDE initialization and probing makes numerous calls to sleep for 50 >>milliseconds while waiting for the interface to return probe status and >>such. > > > Please make it taint the kernel if you do that so we can ignore all the > bug reports. That or justify it with a cite from the ATA standards ? The 50 milliseconds is a pragmatic number you won't find in any standard. Linux IDE driver does the "bang at the door" method of probing, which you won't find in any standard either :) The ATA standard defines times for things like software reset (SRST), but Linux IDE driver takes a unique approach -- just issue down the first command (IDENTIFY DEVICE), and see what you get. The command (or error) responses give you information that allows you to probe further. The 50ms delay hides things like the device coming out of reset, the interface powering up on the first command issued to the device, etc. IMO the number is a "change it at your own risk" number that shouldn't be touched unless the touch-er is also willing to rewrite the IDE driver's probe code ;-) SATA is much faster at probing, and PATA will become progressively less common, so the motivation for changing the probe code is low, too. Jeff