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From: cpcahil@virtech.uucp (Conor P. Cahill)
Newsgroups: comp.unix.i386,comp.unix.xenix,comp.unix.wizards,comp.unix.questions
Subject: Re: Help Needed with Xenix Device Drivers
Keywords: help xenix drivers device kernel
Message-ID: <1990Aug29.113847.958@virtech.uucp>
Date: 29 Aug 90 11:38:47 GMT
References: <24@bmhalh.UUCP>
Reply-To: cpcahil@virtech.UUCP (Conor P. Cahill)
Organization: Virtual Technologies Inc., Sterling VA
Lines: 31

First off, don't do this:

>Followup-To: poster

It gets people mad when they do a follow-up to somebody named poster on the
local machine.  If you want help, just leave the follow-up off.

In article <24@bmhalh.UUCP> bruce@bmhalh.UUCP (Bruce M. Himebaugh) writes:
>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.

This sounds like you are using the u_offset as a short (or int) when it is 
really a long.  The type of u_offset is usually a typedef (off_t) in 
/usr/include/sys/types.h.
>
>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.

Writing a Unix Device Driver
by Janet Egan and Thomas Teixeira
Published by John Wiley & sons.

-- 
Conor P. Cahill            (703)430-9247        Virtual Technologies, Inc.,
uunet!virtech!cpcahil                           46030 Manekin Plaza, Suite 160
                                                Sterling, VA 22170