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Commit c9daa272 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge git://git.kernel.org/pub/scm/linux/kernel/git/wim/linux-2.6-watchdog 

* git://git.kernel.org/pub/scm/linux/kernel/git/wim/linux-2.6-watchdog:
  [WATCHDOG] clarify watchdog operation in documentation
  [WATCHDOG] Revert "Stop looking for device as soon as one is found"
parents 977c8fa4 0d710cba

Documentation/watchdog/watchdog-api.txt

+21 −17
Original line number Original line Diff line number Diff line
@@ -42,23 +42,27 @@ like this source file: see Documentation/watchdog/src/watchdog-simple.c 
A more advanced driver could for example check that a HTTP server is

A more advanced driver could for example check that a HTTP server is

still responding before doing the write call to ping the watchdog.

still responding before doing the write call to ping the watchdog.





When the device is closed, the watchdog is disabled.  This is not

When the device is closed, the watchdog is disabled, unless the "Magic

always such a good idea, since if there is a bug in the watchdog

Close" feature is supported (see below).  This is not always such a

daemon and it crashes the system will not reboot.  Because of this,

good idea, since if there is a bug in the watchdog daemon and it

some of the drivers support the configuration option "Disable watchdog

crashes the system will not reboot.  Because of this, some of the

shutdown on close", CONFIG_WATCHDOG_NOWAYOUT.  If it is set to Y when

drivers support the configuration option "Disable watchdog shutdown on

compiling the kernel, there is no way of disabling the watchdog once

close", CONFIG_WATCHDOG_NOWAYOUT.  If it is set to Y when compiling

it has been started.  So, if the watchdog daemon crashes, the system

the kernel, there is no way of disabling the watchdog once it has been

will reboot after the timeout has passed. Watchdog devices also usually

started.  So, if the watchdog daemon crashes, the system will reboot

support the nowayout module parameter so that this option can be controlled

after the timeout has passed. Watchdog devices also usually support

at runtime.

the nowayout module parameter so that this option can be controlled at



runtime.

Drivers will not disable the watchdog, unless a specific magic character 'V'



has been sent /dev/watchdog just before closing the file.  If the userspace

Magic Close feature:

daemon closes the file without sending this special character, the driver



will assume that the daemon (and userspace in general) died, and will stop

If a driver supports "Magic Close", the driver will not disable the

pinging the watchdog without disabling it first.  This will then cause a

watchdog unless a specific magic character 'V' has been sent to

reboot if the watchdog is not re-opened in sufficient time.

/dev/watchdog just before closing the file.  If the userspace daemon

closes the file without sending this special character, the driver

will assume that the daemon (and userspace in general) died, and will

stop pinging the watchdog without disabling it first.  This will then

cause a reboot if the watchdog is not re-opened in sufficient time.





The ioctl API:

The ioctl API:

drivers/watchdog/w83697hf_wdt.c

+1 −3
Original line number Original line Diff line number Diff line
@@ -382,10 +382,8 @@ wdt_init(void) 
		/* we will autodetect the W83697HF/HG watchdog */

		/* we will autodetect the W83697HF/HG watchdog */

		for (i = 0; ((!found) && (w83697hf_ioports[i] != 0)); i++) {

		for (i = 0; ((!found) && (w83697hf_ioports[i] != 0)); i++) {

			wdt_io = w83697hf_ioports[i];

			wdt_io = w83697hf_ioports[i];

			if (!w83697hf_check_wdt()) {

			if (!w83697hf_check_wdt())

				found++;

				found++;

				break;

			}

		}

		}

	} else {

	} else {

		if (!w83697hf_check_wdt())

		if (!w83697hf_check_wdt())