*BSD News Article 86228


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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: 5-bit limit on SCSI cd devices?
Date: 5 Jan 1997 01:26:18 GMT
Organization: Private BSD site, Dresden
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ljg@PROBLEM_WITH_INEWS_GATEWAY_FILE (Larry Granroth) wrote:

> I would like to hang stacks of cheap SCSI CDROM changers on a FreeBSD 2.2
> box, but there appears to be a limit of 32 device units built into
> the cd driver (a 5-bit CDUNIT).

No, not into the cd driver, but into the entire system. :(  The
macro `dkunit' applies this limit.

There's no actual limit in the cd driver, so you might get around
this by modifying the code.

Btw., CD changers aren't working very excellent anyway.  I have
recently committed a couple of changes that improve the mount
behaviour (you should no longer get ENXIO now), but it still tend to
thrash if accessing multiple platters from the same drive
simultaneously.  I've started a discussion about how to avoid this on
the freebsd-scsi@freebsd.org list, and Peter Dufault has got an idea.

(Said changes are not yet in the 2.2 branch, only in 3.0-current.)

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)