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From: ast@cs.vu.nl (Andy Tanenbaum)
Newsgroups: comp.os.minix
Subject: Re:  Bug reading block special devices (problem solved?)
Message-ID: <1730@botter.cs.vu.nl>
Date: Mon, 12-Oct-87 15:04:59 EDT
Article-I.D.: botter.1730
Posted: Mon Oct 12 15:04:59 1987
Date-Received: Wed, 14-Oct-87 04:47:44 EDT
References: <569@louie.udel.EDU>
Reply-To: ast@cs.vu.nl (Andy Tanenbaum)
Organization: VU Informatica, Amsterdam
Lines: 13

In article <569@louie.udel.EDU> Leisner.Henr@xerox.com (Marty) writes:
>I'm not sure where f_size would come from for a block special device,

Block devices have sizes in MINIX, unlike UNIX.  The sizes are inserted by
mkfs when the file systems are made.  The reason for this is that the 360K
and 1.2M disk drivers are one and the same.  If you insert a 360K diskette
in an AT drive and ask for block 361, it hangs.  As a partial attempt to
solve this problem, I made special files /dev/fd0 and /dev/at0.  The former
has a size of 360K and the latter 1.2M.  If you try to access block 361 on
/dev/fd0, the file system sees that the block is beyond the maximum file
size and returns EOF without even calling the driver.

Andy Tanenbaum (ast@cs.vu.nl)