From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tony Battersby" Subject: RE: [PATCH RFC 0/4] use scatter lists for all blockpc requests and simplify hw handlers Date: Tue, 7 Jun 2005 14:38:29 -0400 Message-ID: <007e01c56b90$1a09a6f0$e0019d89@cybernetics.com> References: <1118162097.4813.38.camel@mulgrave> Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from cyborg.cybernetics.com ([206.246.200.18]:55304 "EHLO cyborg.cybernetics.com") by vger.kernel.org with ESMTP id S261855AbVFGSiU (ORCPT ); Tue, 7 Jun 2005 14:38:20 -0400 In-Reply-To: <1118162097.4813.38.camel@mulgrave> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: 'James Bottomley' Cc: 'Douglas Gilbert' , 'Mike Christie' , 'device-mapper development' , 'linux-scsi' , 'Jens Axboe' , LIRANS@il.ibm.com > > My company (Cybernetics) sells several products that run embedded Linux > > which use the userspace scatter-gather capability of the SG driver. > > They are still running the 2.4 kernel series, but we will probably > > switch to 2.6 at some point. > > What do they actually use it for? As in why is the data scattered even > in the virtual address space? One of our products is a RAID-like controller for SCSI tape drives. Parallel SCSI or iSCSI in via a target-mode SCSI driver and parallel SCSI, iSCSI, or FC out via the SG driver, with various functions in between for data buffering, emulation, striping, mirroring, etc. The program that controls everything has a complex internal buffering scheme that uses userspace scatter-gather for the main read/write I/O path to the tape drives. Anthony J. Battersby Cybernetics