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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: Re: Device driver timeout question ...
Message-ID: <8109@mimsy.UUCP>
Date: Sun, 23-Aug-87 14:55:38 EDT
Article-I.D.: mimsy.8109
Posted: Sun Aug 23 14:55:38 1987
Date-Received: Mon, 24-Aug-87 00:00:28 EDT
References: <570@obiwan.UUCP> <533@micas.UUCP> <474@mtxinu.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 51

In article <474@mtxinu.UUCP> ed@mtxinu.UUCP (Ed Gould) writes:
>untimeout() has been part of BSD-derived systems since at least 4.2BSD;
>I don't remember for sure if it was in 4.1, but I imagine that it was.

As I recall, we had to install untimeout() when we installed CMU
IPC.

Anyway, as to watchdog timers, untimeout() seems unnecessary:

	fooopen(dev, flag)
		dev_t dev;
		int flag;
	{
		...
		s = spl5();
		/* start the watchdog timer, if necessary */
		foostate = FOO_OPEN;
		if (foowstart == 0) {
			timeout(foowatch, (caddr_t)0, hz);
			foowstart++;
		}
		splx(s);
		...
	}

	fooclose(dev)
		dev_t dev;
	{

		foostate = FOO_CLOSED;
		...
	}

	/* check on the foo once a second */
	foowatch()
	{

		/* stop timing if we have closed down the foo */
		if (foostate == FOO_CLOSED) {
			foowstart = 0;	/* and remember to restart */
			return;
		}
		timeout(foowatch, (caddr_t)0, hz);
		...
	}

Or, as I do in my UDA50 driver, let the timer run always.  (Someday
I may move the timer to uba.c.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	seismo!mimsy!chris