From owner-freebsd-current Tue Dec 15 19:36:22 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id TAA13614 for freebsd-current-outgoing; Tue, 15 Dec 1998 19:36:22 -0800 (PST) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from allegro.lemis.com (allegro.lemis.com [192.109.197.134]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id TAA13609 for ; Tue, 15 Dec 1998 19:36:16 -0800 (PST) (envelope-from grog@freebie.lemis.com) Received: from freebie.lemis.com (freebie.lemis.com [192.109.197.137]) by allegro.lemis.com (8.9.1/8.9.0) with ESMTP id OAA03849; Wed, 16 Dec 1998 14:06:03 +1030 (CST) Received: (from grog@localhost) by freebie.lemis.com (8.9.1/8.9.0) id OAA24619; Wed, 16 Dec 1998 14:06:04 +1030 (CST) Message-ID: <19981216140604.H15815@freebie.lemis.com> Date: Wed, 16 Dec 1998 14:06:04 +1030 From: Greg Lehey To: Dan Strick Cc: freebsd-current@FreeBSD.ORG Subject: Re: Tape Driver Changes Proposed: Tape Early Warning Behaviour References: <199812160331.TAA19404@math.berkeley.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.91.1i In-Reply-To: <199812160331.TAA19404@math.berkeley.edu>; from Dan Strick on Tue, Dec 15, 1998 at 07:31:33PM -0800 WWW-Home-Page: http://www.lemis.com/~grog Organization: LEMIS, PO Box 460, Echunga SA 5153, Australia Phone: +61-8-8388-8286 Fax: +61-8-8388-8725 Mobile: +61-41-739-7062 Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Tuesday, 15 December 1998 at 19:31:33 -0800, Dan Strick wrote: >> I can't see any particular reason to restrict the minor number format >> if it's not necessary. So we have 4 densities, n (<=4?) speeds and >> compression. That makes 5 bits. Then we have non-rewind, a maximum >> of 16 units per drive and (on a PC) probably not more than 16 >> controllers. A total of 14 bits of minor number out of the 24 >> available: in other words, there should be no problem finding a minor >> number format which fits. > > One good reason for restricting the minor number format is that 16384 > (i.e. 2^14) different entries for tape devices in /dev would be painful > beyound belief. You wouldn't automatically create all device nodes, just those that corresponded to real devices and their functions. > I claim that the idea of specifying tape drive operating parameters > via minor device number was a really bad idea from almost the very > beginning (unix v6 I believe) and should have been abandoned after > the ioctl() system call became available. How would you tell tar to make a backup, this time only, which didn't compress? If you did it with mt(1), how would you ensure that nobody dicked with the settings between your running mt(1) and tar(1)? Greg -- See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message