From mboxrd@z Thu Jan 1 00:00:00 1970 From: Douglas Gilbert Subject: Re: [PATCH] sym2: remove code to handle DMA_BIDIRECTION requests Date: Thu, 15 Sep 2005 22:12:33 +1000 Message-ID: <43296531.5090709@torque.net> References: <20050914134131.GA9700@lst.de> Reply-To: dougg@torque.net Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from zorg.st.net.au ([203.16.233.9]:21436 "EHLO borg.st.net.au") by vger.kernel.org with ESMTP id S1751168AbVIOML5 (ORCPT ); Thu, 15 Sep 2005 08:11:57 -0400 In-Reply-To: <20050914134131.GA9700@lst.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Christoph Hellwig Cc: matthew@wil.cx, linux-scsi@vger.kernel.org Christoph Hellwig wrote: > The upper layer doesn't send these down since 2.4.x (or 2.6 in > practice), so no need to handle it. Inline sym_setup_data_pointers > into it's only caller so we can fail gracefully in the case we'd get > one neverless. Christoph, I have no objection to this patch. I would like to flag that at some stage in the future the SCSI (or whatever it may be called) subsystem will need to support true bidirectional commands (there are a few of these in SBC-2 and lots of them in OSD). To do it properly I think we need two scatter gather lists, one for data out (to the device) and one for data in (from the device). The SBC-2 XDWRITEREAD command indicates that the data out is done before the data in (from the device); I'm not sure whether that ordering is always the case. Doug Gilbert