From owner-freebsd-hackers Sun Jul 5 13:44:22 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id NAA01209 for freebsd-hackers-outgoing; Sun, 5 Jul 1998 13:44:22 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from smtp04.primenet.com (root@smtp04.primenet.com [206.165.6.134]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id NAA01196; Sun, 5 Jul 1998 13:44:19 -0700 (PDT) (envelope-from tlambert@usr08.primenet.com) Received: (from daemon@localhost) by smtp04.primenet.com (8.8.8/8.8.8) id MAA19389; Sun, 5 Jul 1998 12:11:41 -0700 (MST) Received: from usr08.primenet.com(206.165.6.208) via SMTP by smtp04.primenet.com, id smtpd019377; Sun Jul 5 12:11:40 1998 Received: (from tlambert@localhost) by usr08.primenet.com (8.8.5/8.8.5) id MAA26965; Sun, 5 Jul 1998 12:11:38 -0700 (MST) From: Terry Lambert Message-Id: <199807051911.MAA26965@usr08.primenet.com> Subject: Re: block device on wst device. To: julian@whistle.com (Julian Elischer) Date: Sun, 5 Jul 1998 19:11:38 +0000 (GMT) Cc: hackers@FreeBSD.ORG, sos@FreeBSD.ORG In-Reply-To: from "Julian Elischer" at Jul 4, 98 01:58:28 pm X-Mailer: ELM [version 2.4 PL25] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > ther is a block interface to wst > > is this used by anyone? > does it work? > > I think the block interface should go away > as it doesn't really make much sense on tapes. > (same for wt.c) > > In effect it went a way some time ago for st.c I still see this as a problem, specifically for tape devices. I see the block device for tape drives capable of providing a kernel side buffer that is not statically allocated to a particular driver and which provides bufferring for streaming tape devices. The examples I can come up with where the user space write to the buffer should return immediately so that the user space program can read, and therefore overlap physical tape and disk I/O, are DAT devices and QIC-40/80/120/etc. devices. This is specifically relevent to the FT (QIC-40/etc.) devices because of there use of a (normally) non-FIFO-ed serial interface, to wit, the floppy controller. Some people will say "yeah, but no one with any sense uses those"; however, I could make the same argument against IDE on the same basis (specifically, number of tagged commands drives allow in their queues). For a destop machine, cheap is often good enough, and FT drives are certainly cheap. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message