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-rw-r--r--Documentation/watchdog/watchdog-kernel-api.txt33
1 files changed, 33 insertions, 0 deletions
diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
index 7f31125c123e..ea277478982f 100644
--- a/Documentation/watchdog/watchdog-kernel-api.txt
+++ b/Documentation/watchdog/watchdog-kernel-api.txt
@@ -48,8 +48,10 @@ struct watchdog_device {
const struct attribute_group **groups;
const struct watchdog_info *info;
const struct watchdog_ops *ops;
+ const struct watchdog_governor *gov;
unsigned int bootstatus;
unsigned int timeout;
+ unsigned int pretimeout;
unsigned int min_timeout;
unsigned int max_timeout;
unsigned int min_hw_heartbeat_ms;
@@ -74,9 +76,11 @@ It contains following fields:
* info: a pointer to a watchdog_info structure. This structure gives some
additional information about the watchdog timer itself. (Like it's unique name)
* ops: a pointer to the list of watchdog operations that the watchdog supports.
+* gov: a pointer to the assigned watchdog device pretimeout governor or NULL.
* timeout: the watchdog timer's timeout value (in seconds).
This is the time after which the system will reboot if user space does
not send a heartbeat request if WDOG_ACTIVE is set.
+* pretimeout: the watchdog timer's pretimeout value (in seconds).
* min_timeout: the watchdog timer's minimum timeout value (in seconds).
If set, the minimum configurable value for 'timeout'.
* max_timeout: the watchdog timer's maximum timeout value (in seconds),
@@ -121,6 +125,7 @@ struct watchdog_ops {
int (*ping)(struct watchdog_device *);
unsigned int (*status)(struct watchdog_device *);
int (*set_timeout)(struct watchdog_device *, unsigned int);
+ int (*set_pretimeout)(struct watchdog_device *, unsigned int);
unsigned int (*get_timeleft)(struct watchdog_device *);
int (*restart)(struct watchdog_device *);
void (*ref)(struct watchdog_device *) __deprecated;
@@ -188,6 +193,23 @@ they are supported. These optional routines/operations are:
If set_timeout is not provided but, WDIOF_SETTIMEOUT is set, the watchdog
infrastructure updates the timeout value of the watchdog_device internally
to the requested value.
+ If the pretimeout feature is used (WDIOF_PRETIMEOUT), then set_timeout must
+ also take care of checking if pretimeout is still valid and set up the timer
+ accordingly. This can't be done in the core without races, so it is the
+ duty of the driver.
+* set_pretimeout: this routine checks and changes the pretimeout value of
+ the watchdog. It is optional because not all watchdogs support pretimeout
+ notification. The timeout value is not an absolute time, but the number of
+ seconds before the actual timeout would happen. It returns 0 on success,
+ -EINVAL for "parameter out of range" and -EIO for "could not write value to
+ the watchdog". A value of 0 disables pretimeout notification.
+ (Note: the WDIOF_PRETIMEOUT needs to be set in the options field of the
+ watchdog's info structure).
+ If the watchdog driver does not have to perform any action but setting the
+ watchdog_device.pretimeout, this callback can be omitted. That means if
+ set_pretimeout is not provided but WDIOF_PRETIMEOUT is set, the watchdog
+ infrastructure updates the pretimeout value of the watchdog_device internally
+ to the requested value.
* get_timeleft: this routines returns the time that's left before a reset.
* restart: this routine restarts the machine. It returns 0 on success or a
negative errno code for failure.
@@ -268,3 +290,14 @@ User should follow the following guidelines for setting the priority:
* 128: default restart handler, use if no other handler is expected to be
available, and/or if restart is sufficient to restart the entire system
* 255: highest priority, will preempt all other restart handlers
+
+To raise a pretimeout notification, the following function should be used:
+
+void watchdog_notify_pretimeout(struct watchdog_device *wdd)
+
+The function can be called in the interrupt context. If watchdog pretimeout
+governor framework (kbuild CONFIG_WATCHDOG_PRETIMEOUT_GOV symbol) is enabled,
+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.