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From: emjej@uokvax.UUCP
Newsgroups: net.micro.6809
Subject: Re: Orphaned Response
Message-ID: <3500146@uokvax.UUCP>
Date: Mon, 5-May-86 11:17:00 EDT
Article-I.D.: uokvax.3500146
Posted: Mon May  5 11:17:00 1986
Date-Received: Sat, 10-May-86 23:45:31 EDT
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Nf-From: uokvax.UUCP!emjej    May  5 10:17:00 1986


/* Written 10:41 am  Apr 22, 1986 by ingoldsby@calgary.UUCP in net.micro.6809 */
    One final question: Is it permissible to do system calls within
a device driver?

				Terry Ingoldsby
/* End of text from net.micro.6809 */

Yes, indeed, one can.  I once asked Kim Kempf (God, I'm starting to sound
like Jerry Pournelle!) and he said yes, in fact, Seikou Electronics, the
folks who do nice things in Japan, do just that.  Qualifying data: the
particular system calls they did were doing I/O calls from within a device
driver (though I've seen a device driver that does a request for memory
with no sweat, so there's another example), and if you try that, remember
to use *system* path #s, not the 0, 1, 2, ... relative to the process that
you may have in mind.  Further qualifying--the reason I asked is that I
wanted to make up for a FLEXoid nerd processor (SCREDITOR III) asking for
sole control of the printer by setting up a device that when opened would
fork the spooler and feed things written to it to the spooler.  Kim wasn't
sure whether that would actually work, and I haven't tried it (because I
would have to write a file manager, and I can't find docs for the entry
points for 6809 file managers and where parameters are kept), so I don't
know either.

						James Jones