From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756522Ab2BFXBD (ORCPT ); Mon, 6 Feb 2012 18:01:03 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:49198 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756218Ab2BFXA7 convert rfc822-to-8bit (ORCPT ); Mon, 6 Feb 2012 18:00:59 -0500 MIME-Version: 1.0 In-Reply-To: <5C167A1D-2203-4F1C-B538-E99DD87E7E42@bootc.net> References: <4E4BD560.4010806@bootc.net> <4E4D3B88.30003@ladisch.de> <4F29978A.3010707@redhat.com> <20120201224156.0773ebc6@stein> <4F2A55B9.4040005@panasas.com> <4F2A60DC.9030007@ladisch.de> <4F2FD1F4.9050702@bootc.net> <4F2FE705.3070509@ladisch.de> <4F2FE8DA.70502@bootc.net> <20120206212628.6880c506@stein> <5C167A1D-2203-4F1C-B538-E99DD87E7E42@bootc.net> From: Julian Calaby Date: Tue, 7 Feb 2012 10:00:38 +1100 Message-ID: Subject: Re: FireWire/SBP2 Target mode To: Chris Boot Cc: Stefan Richter , Clemens Ladisch , target-devel@vger.kernel.org, linux1394-devel@lists.sourceforge.net, Boaz Harrosh , Andy Grover , linux-scsi@vger.kernel.org, lkml Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Tue, Feb 7, 2012 at 09:28, Chris Boot wrote: > On 6 Feb 2012, at 20:26, Stefan Richter wrote: > >> On Feb 06 Chris Boot wrote: >>> On 06/02/2012 14:43, Clemens Ladisch wrote: >>>> Chris Boot wrote: >>>>> You can pull the code from: >>>>> git://github.com/bootc/Linux-SBP-2-Target.git >>>> >>>> The TODO file says: >>>>> * Update Juju so we can get the speed in the fw_address_handler callback >>>> >>>> What is the speed needed for? >>> >>> "The speed at which the block write request to the MANAGEMENT_AGENT >>> register is received shall determine the speed used by the target for >>> all subsequent requests to read the initiator’s configuration ROM, fetch >>> ORB’s from initiator memory or store status at the initiator’s >>> status_FIFO. Command block ORB’s separately specify the speed for >>> requests addressed to the data buffer or page table." >>> >>> (T10/1155D Revision 4 page 53/54) >> >> I guess it is not too hard to add this to the AR-req handler.  On the >> other hand, I see little reason to follow the SBP-2 spec to the letter >> here.  The target driver could just use the maximum speed that the core >> figured out.  On the other hand, this requires of course >>  - the target to wait for core to finish scanning an initiator, >>  - the core to offer an API to look up an fw_device by a >>    card--generation--nodeID tuple. >> >> The intention of the spec is IMO clearly to enable target implementations >> that do not need to implement topology scanning.  I have a hard time to >> think of a valid scenario where an initiator needs to be able to steer a >> target towards a lower wire speed than what the participating links and >> PHYs actually support. > > The only thing stopping me from getting the speed is the fact that struct fw_request is opaque. The value is easily available from request->response.speed and I kind of do that already in a very hackish way. I've sent a separate patch which adds a function that can be used to access that one value. > > Waiting until the bus scan is complete isn't actually that great as I see the first LOGIN requests often before the fw_node is seen at all. I'd have to turn away the requester and hope they try again. I'm fairly sure my little tweak in my patch is a simple enough solution. Stupid question: Could you use a completion queue or something equivalent to wait until you have seen the fw_node, *then* process the LOGIN request? Thanks, -- Julian Calaby Email: julian.calaby@gmail.com Profile: http://www.google.com/profiles/julian.calaby/ .Plan: http://sites.google.com/site/juliancalaby/