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- Newsgroups: comp.sys.mac.programmer
- Path: sparky!uunet!mcsun!fuug!funic!nntp.hut.fi!vipunen.hut.fi!jmunkki
- From: jmunkki@vipunen.hut.fi (Juri Munkki)
- Subject: Re: Writing asynchronous SCSI driver.
- Message-ID: <1992Jul29.205201.2090@nntp.hut.fi>
- Sender: usenet@nntp.hut.fi (Usenet pseudouser id)
- Nntp-Posting-Host: vipunen.hut.fi
- Reply-To: jmunkki@vipunen.hut.fi (Juri Munkki)
- Organization: Helsinki University of Technology
- References: <HEYES.92Jul21092205@dadev.cebaf.gov> <14h8tkINN61k@early-bird.think.com>
- Distribution: comp.sys.mac.programmer
- Date: Wed, 29 Jul 1992 20:52:01 GMT
- Lines: 31
-
- In article <14h8tkINN61k@early-bird.think.com> ephraim@think.com (Ephraim Vishniac) writes:
- >In article <HEYES.92Jul21092205@dadev.cebaf.gov> heyes@dadev.cebaf.gov (Graham Heyes) writes:
- >>2) How do I make a "task" which wants to use the driver pend
- >> until the current transaction has completed?
- >
- >You don't.
- >
- >> This is probably doccumented somewhere but a code
- >>example would be a great help.
- >
- >The appropriate documentation firmly discourages developers from
- >attempting to implement asynchronous device drivers. Even if you did,
- >it's up to the application to request asynch I/O (see the Device
- >Manager chapter of IM), which none of them do.
-
- I agree here, but maybe the time could be used for something pseudo-
- useful anyway. You could write a routine that calculates a pixel
- in the mandelbrot set or ray traces something while waiting for the
- disk. You would have to code this into the driver, but it might
- be possible to make it open enough so that applications could register
- with your driver to get some calculation time.
-
- Of course, this isn't asynchronous I/O, but it would be an interesting
- way to see how much time a Macintosh normally spends in these busy
- waiting loops of the SCSI driver.
-
- Disclaimer: :-) [I've gotta be kidding, right?]
-
- --
- Juri Munkki Windsurf: fast sailing
- jmunkki@hut.fi Macintosh: fast software
-