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From: bruce@bmhalh.UUCP (Bruce M. Himebaugh)
Newsgroups: comp.unix.i386,comp.unix.xenix,comp.unix.wizards,comp.unix.questions
Subject: Help Needed with Xenix Device Drivers
Keywords: help xenix drivers device kernel
Message-ID: <24@bmhalh.UUCP>
Date: 19 Aug 90 14:09:33 GMT
Followup-To: poster
Organization: Bruce M. Himebaugh
Lines: 27

I am writing a character device driver under SCO Xenix (v2.3.3) and have run
across a stumbling block.  During the read and write functions I wish to
access the current file postition (as set by lseek(S)).  Per the documentation
that I have I access the element u_offset in the 'u' structure.  This works
great for 0-65535.  But, when I tell lseek(S) to move to postition 65536 the
value of u_offset gets set to 0 and if I move to 65537 it gets set to 1, etc.
I have the feeling that u_offset is just a an offset into the current segment
and when accessing values outside 65535 I am actually moving the file pointer
into another segment, but how do I tell what that segment is?  Hopefully I am
partially on the right track, but if I'm not I would appreciate some direction.
I have programmed in C for quite a while, but am just now tackling device
drivers.

A second question is, where can I get a book (or books) on writing XENIX device
drivers?  I have a book on UNIX device drivers, but Xenix is enough different
that it doesn't answer all my questions.

Any help on these two questions will be GREATLY appreciated.

Thanks,

Bruce
-- 
Bruce M. Himebaugh                                          Voice: 216-484-3528
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