[WATCHDOG] Pre-Timeout flags

Some watchdog timers support the concept of a "pretimeout" which
occurs some time before the real timeout.  The pretimeout can
be delivered via an interrupt or NMI and can be used to panic
the system when it occurs (so you get useful information instead
of a blind reboot).

Signed-off-by: Corey Minyard <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Documentation/watchdog/watchdog-api.txt

@@ -110,7 +110,31 @@ current timeout using the GETTIMEOUT ioctl.
     ioctl(fd, WDIOC_GETTIMEOUT, &timeout);
     printf("The timeout was is %d seconds\n", timeout);
 
-Envinronmental monitoring:
+Pretimeouts:
+
+Some watchdog timers can be set to have a trigger go off before the
+actual time they will reset the system.  This can be done with an NMI,
+interrupt, or other mechanism.  This allows Linux to record useful
+information (like panic information and kernel coredumps) before it
+resets.
+
+    pretimeout = 10;
+    ioctl(fd, WDIOC_SETPRETIMEOUT, &pretimeout);
+
+Note that the pretimeout is the number of seconds before the time
+when the timeout will go off.  It is not the number of seconds until
+the pretimeout.  So, for instance, if you set the timeout to 60 seconds
+and the pretimeout to 10 seconds, the pretimout will go of in 50
+seconds.  Setting a pretimeout to zero disables it.
+
+There is also a get function for getting the pretimeout:
+
+    ioctl(fd, WDIOC_GETPRETIMEOUT, &timeout);
+    printf("The pretimeout was is %d seconds\n", timeout);
+
+Not all watchdog drivers will support a pretimeout.
+
+Environmental monitoring:
 
 All watchdog drivers are required return more information about the system,
 some do temperature, fan and power level monitoring, some can tell you
@@ -169,6 +193,10 @@ The watchdog saw a keepalive ping since it was last queried.
 
 	WDIOF_SETTIMEOUT	Can set/get the timeout
 
+The watchdog can do pretimeouts.
+
+	WDIOF_PRETIMEOUT	Pretimeout (in seconds), get/set
+
 
 For those drivers that return any bits set in the option field, the
 GETSTATUS and GETBOOTSTATUS ioctls can be used to ask for the current

include/linux/watchdog.h

@@ -28,6 +28,8 @@ struct watchdog_info {
 #define	WDIOC_KEEPALIVE		_IOR(WATCHDOG_IOCTL_BASE, 5, int)
 #define	WDIOC_SETTIMEOUT        _IOWR(WATCHDOG_IOCTL_BASE, 6, int)
 #define	WDIOC_GETTIMEOUT        _IOR(WATCHDOG_IOCTL_BASE, 7, int)
+#define	WDIOC_SETPRETIMEOUT	_IOWR(WATCHDOG_IOCTL_BASE, 8, int)
+#define	WDIOC_GETPRETIMEOUT	_IOR(WATCHDOG_IOCTL_BASE, 9, int)
 
 #define	WDIOF_UNKNOWN		-1	/* Unknown flag error */
 #define	WDIOS_UNKNOWN		-1	/* Unknown status error */
@@ -41,6 +43,7 @@ struct watchdog_info {
 #define WDIOF_POWEROVER		0x0040	/* Power over voltage */
 #define WDIOF_SETTIMEOUT	0x0080  /* Set timeout (in seconds) */
 #define WDIOF_MAGICCLOSE	0x0100	/* Supports magic close char */
+#define	WDIOF_PRETIMEOUT	0x0200  /* Pretimeout (in seconds), get/set */
 #define	WDIOF_KEEPALIVEPING	0x8000	/* Keep alive ping reply */
 
 #define	WDIOS_DISABLECARD	0x0001	/* Turn off the watchdog timer */