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-rw-r--r--Documentation/watchdog/watchdog-api.txt30
1 files changed, 29 insertions, 1 deletions
diff --git a/Documentation/watchdog/watchdog-api.txt b/Documentation/watchdog/watchdog-api.txt
index 21ed511..7dc2c1c 100644
--- a/Documentation/watchdog/watchdog-api.txt
+++ b/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
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