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-rw-r--r--Documentation/watchdog/watchdog-kernel-api.rst12
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/watchdog/watchdog-kernel-api.rst b/Documentation/watchdog/watchdog-kernel-api.rst
index 068a55ee0d4a..baf44e986b07 100644
--- a/Documentation/watchdog/watchdog-kernel-api.rst
+++ b/Documentation/watchdog/watchdog-kernel-api.rst
@@ -336,3 +336,15 @@ an action is taken by a preconfigured pretimeout governor preassigned to
the watchdog device. If watchdog pretimeout governor framework is not
enabled, watchdog_notify_pretimeout() prints a notification message to
the kernel log buffer.
+
+To set the last known HW keepalive time for a watchdog, the following function
+should be used::
+
+ int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd,
+ unsigned int last_ping_ms)
+
+This function must be called immediately after watchdog registration. It
+sets the last known hardware heartbeat to have happened last_ping_ms before
+current time. Calling this is only needed if the watchdog is already running
+when probe is called, and the watchdog can only be pinged after the
+min_hw_heartbeat_ms time has passed from the last ping.