From owner-freebsd-scsi@FreeBSD.ORG Thu Feb 2 22:06:35 2006 Return-Path: X-Original-To: freebsd-scsi@freebsd.org Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9B97A16A420; Thu, 2 Feb 2006 22:06:35 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.FreeBSD.org (Postfix) with ESMTP id A7A0F43D45; Thu, 2 Feb 2006 22:06:34 +0000 (GMT) (envelope-from scottl@samsco.org) Received: from [192.168.254.11] (junior.samsco.home [192.168.254.11]) (authenticated bits=0) by pooker.samsco.org (8.13.4/8.13.4) with ESMTP id k12M6VHN042931; Thu, 2 Feb 2006 15:06:32 -0700 (MST) (envelope-from scottl@samsco.org) Message-ID: <43E28272.30704@samsco.org> Date: Thu, 02 Feb 2006 15:06:42 -0700 From: Scott Long User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.12) Gecko/20051230 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Matthew Jacob References: <20060130202806.DCC7916A4CA@hub.freebsd.org> <43DEF43A.6090804@root.org> <20060130213338.H79194@ns1.feral.com> <200601311239.10248.flz@xbsd.org> <43E06B06.80405@root.org> <20060202175041.GA92109@nargothrond.kdm.org> <20060202095828.D97756@ns1.feral.com> <43E252EC.1050803@root.org> <43E25C4D.9020804@samsco.org> <43E2650D.1060109@root.org> <20060202130620.A99168@ns1.feral.com> <43E27E58.4020606@samsco.org> <20060202135123.K99168@ns1.feral.com> In-Reply-To: <20060202135123.K99168@ns1.feral.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-1.4 required=3.8 tests=ALL_TRUSTED autolearn=failed version=3.1.0 X-Spam-Checker-Version: SpamAssassin 3.1.0 (2005-09-13) on pooker.samsco.org Cc: freebsd-scsi@freebsd.org, Florent Thoumie , "Kenneth D. Merry" , Nate Lawson Subject: Re: cvs commit: src/sys/cam/scsi scsi_da.c src/sys/dev/usb umass.c usbdevs X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Feb 2006 22:06:35 -0000 Matthew Jacob wrote: >>> >>> >>> And how will you distinguish between "not currently enabled" and "not >>> supported"? >>> >> >> If WCE is not supported, will the device lie and report the WCE bit as >> set? >> > > No. But a device could have it turned off and you wouldn't then infer > that you *could*. I guess I don't follow. There was a suggestion to read page 8 during the da device probe, cache the WCE value, and act on it accordingly later on. There was also a suggestion to read the page on demand as part of the immediate decision to do the SYNC CACHE. As much of a hassle as it could be, the latter is likely the better approach as it eliminates the messy state tracking that you'd have to do on the user. Who wants to hack up the pass driver to trap mode page writes and then try to correlate which da device to pass that info on to? And yeah, if the device is able to change the state on its own, there is no way the first approach can work. Scott