From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: use_10_for_ms revisited? Date: Sun, 29 Jun 2003 13:58:04 -0400 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <3EFF28AC.104@pobox.com> References: <3EFE8784.4000101@pobox.com> <20030629102222.GA14962@win.tue.nl> <3EFF14BD.3030406@pobox.com> <20030629173632.GA15024@win.tue.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:9874 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S265712AbTF2Rn4 (ORCPT ); Sun, 29 Jun 2003 13:43:56 -0400 In-Reply-To: <20030629173632.GA15024@win.tue.nl> List-Id: linux-scsi@vger.kernel.org To: Andries Brouwer Cc: linux-scsi@vger.kernel.org Andries Brouwer wrote: > Two that I have right here yield 0 80 2 2 20 0 0 0 and > 0 80 0 2 1F 0 0 0, respectively. (All in hex.) Ok, you've convinced me I found an ATAPI-only rule that doesn't apply to USB :) Thanks. > [I did introduce this use_10_for_ms; it allows a very large > cleanup in the usb-storage code. Submitted the SCSI part of > the patch and waited for it to be applied. That took a while > and when it went in I was a bit short on Linux time. So Matt > got impatient and started doing the rest himself. He patched > sr.c - something I would not have done, I considered the SCSI > part settled - perhaps things broke a bit but James went in and > fixed some things again. So maybe we are now again ready for > the intended large cleanup. I would like to see that done, > and afterwards see this area stable for a few kernel versions.] I would still prefer to detect "MMC", at least in ATAPI's case, and then use that flag to trickle down knowledge to use_10_for_ms and similar features. ATAPI is even easier than I was previously thinking: at host-alloc time, we already know the devices will be MMC, and never ever want 6-byte commands. I grant you that ATAPI is not the whole world, here, but it presents sufficient cases to warrant a common approach. Both ide-scsi and usb storage (and my ata-scsi driver) have atapi-specific logic in them for 6-to-10 translation. We can keep adding hueristic upon hueristic to the kernel to handle these things, or we can step back, look at the bigger picture, and take advantage of the commonality found. Stepping back a bit and addressing previous "standards versus reality" comments (), I certainly understand the point, and am used to such things in all areas of hardware :) My main point was that -- at least wrt ATAPI -- the scsi MMC standards seem to be moving in the direction of codifying _existing practice_, not making up new standards. IOW, they are just writing down the things that have been in the field for years. Jeff