From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: PMP and SEMB messages to SEP Date: Mon, 17 Jan 2011 11:21:46 -0600 Message-ID: <1295284906.3015.136.camel@mulgrave.site> References: <20110113192558.GE16039@MAIL.13thfloor.at> <20110114142018.GA978@htj.dyndns.org> <20110114165957.GH16039@MAIL.13thfloor.at> <20110114170407.GE978@htj.dyndns.org> <20110114173759.GI16039@MAIL.13thfloor.at> <20110117154042.GG27123@htj.dyndns.org> <1295281131.3015.44.camel@mulgrave.site> <20110117171836.GI27123@htj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from cantor.suse.de ([195.135.220.2]:36035 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753425Ab1AQRVx (ORCPT ); Mon, 17 Jan 2011 12:21:53 -0500 In-Reply-To: <20110117171836.GI27123@htj.dyndns.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: Herbert Poetzl , linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org On Mon, 2011-01-17 at 18:18 +0100, Tejun Heo wrote: > Hello, James. > > On Mon, Jan 17, 2011 at 10:18:51AM -0600, James Bottomley wrote: > > > The problem is that the PMP device itself is currently not allocated a > > > userland visible device, so it doesn't have any /dev/* node. Hmmm... > > > > So perhaps it should be. If you look at the equivalent topology on SAS, > > our expanders have a bsg device node precisely so that we can do this. > > > > That said, SAS expanders have a defined protocol (SAS Management > > Protocol) to talk to the outside world, so they are real visible objects > > always in our topology ... I'm not sure PMP has this ... it seems that > > all PMP visibility is an extension to the standard? > > SATA PMP is mostly a dumb switch and there isn't much which can be > done by issuing custom commands (and IIRC we didn't have bsg back > then), so it was never made visible to userland, but yeah probably > exporting a bsg node is a good idea. Inside libata, the PMP device > has its device representation and all so it shouldn't be too difficult > either. Not really sure how the inquiry and stuff should be handled > tho. Expanders aren't SCSI devices either ... that means they don't appear as visible to standard SCSI mechanisms like INQUIRY (SMP isn't a SCSI protocol it's a SAS extension). They just appear as part of the topology in the device tree. James