linux-kernel - Questions about Watch Dog Timer under Linux.

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Message-ID: <f9f38a550912090647q5af6cb14w84ea8d9223d82bd9@mail.gmail.com>
Date:	Wed, 9 Dec 2009 22:47:28 +0800
From:	Cypher Wu <cypher.w@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Questions about Watch Dog Timer under Linux.

I'm used to work on embedded systems, the Watch Dog Timer in our
products is usually a seperate chip on the board wich will start to
work after power reset and will time out in 2 seconds. The system has
to start dog clearing from the very beginning and there have no way to
disable WDT.
Now I want to use WDT under Linux, while I read
Documentation/watchdog/watchdog-api.txt and then look though some
drivers of WDT under Linux, it seems WDT under Linux has to be able to
be disabled, and it will be disabled from the beginning, and starting
to work after the application open the special driver file?  The
sample code under Linux use a very bigger time span than our embedded
system:
	while (1) {
		ret = write(fd, "\0", 1);
		if (ret != 1) {
			ret = -1;
			break;
		}
		ret = fsync(fd);
		if (ret)
			break;
		sleep(10);
	}


Is this the pattern we have to follow to use WDT under Linux? We have
to choose a chip as WDT, and it seems the chip we've familiar under
embedded systems can't be used under Linux?
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