unsigned int timeout;
unsigned int min_timeout;
unsigned int max_timeout;
+ unsigned int max_hw_heartbeat_ms;
struct notifier_block reboot_nb;
struct notifier_block restart_nb;
void *driver_data;
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.
* 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.
* min_timeout: the watchdog timer's minimum timeout value (in seconds).
-* max_timeout: the watchdog timer's maximum timeout value (in seconds).
+ If set, the minimum configurable value for 'timeout'.
+* max_timeout: the watchdog timer's maximum timeout value (in seconds),
+ as seen from userspace. If set, the maximum configurable value for
+ 'timeout'. Not used if max_hw_heartbeat_ms is non-zero.
+* max_hw_heartbeat_ms: Maximum hardware heartbeat, in milli-seconds.
+ If set, the infrastructure will send heartbeats to the watchdog driver
+ if 'timeout' is larger than max_hw_heartbeat_ms, unless WDOG_ACTIVE
+ is set and userspace failed to send a heartbeat for at least 'timeout'
+ seconds.
* reboot_nb: notifier block that is registered for reboot notifications, for
internal use only. If the driver calls watchdog_stop_on_reboot, watchdog core
will stop the watchdog on such notifications.
* stop: with this routine the watchdog timer device is being stopped.
The routine needs a pointer to the watchdog timer device structure as a
parameter. It returns zero on success or a negative errno code for failure.
- Some watchdog timer hardware can only be started and not be stopped. The
- driver supporting this hardware needs to make sure that a start and stop
- routine is being provided. This can be done by using a timer in the driver
- that regularly sends a keepalive ping to the watchdog timer hardware.
+ Some watchdog timer hardware can only be started and not be stopped.
+ If a watchdog can not be stopped, the watchdog driver must set the
+ WDOG_HW_RUNNING flag in its stop function to inform the watchdog core that
+ the watchdog is still running.
Not all watchdog timer hardware supports the same functionality. That's why
all other routines/operations are optional. They only need to be provided if
and -EIO for "could not write value to the watchdog". On success this
routine should set the timeout value of the watchdog_device to the
achieved timeout value (which may be different from the requested one
- because the watchdog does not necessarily has a 1 second resolution).
+ because the watchdog does not necessarily have a 1 second resolution).
+ Drivers implementing max_hw_heartbeat_ms set the hardware watchdog heartbeat
+ to the minimum of timeout and max_hw_heartbeat_ms. Those drivers set the
+ timeout value of the watchdog_device either to the requested timeout value
+ (if it is larger than max_hw_heartbeat_ms), or to the achieved timeout value.
(Note: the WDIOF_SETTIMEOUT 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.timeout, this callback can be omitted.
+ 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.
* 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.
The status bits should (preferably) be set with the set_bit and clear_bit alike
bit-operations. The status bits that are defined are:
* WDOG_ACTIVE: this status bit indicates whether or not a watchdog timer device
- is active or not. When the watchdog is active after booting, then you should
- set this status bit (Note: when you register the watchdog timer device with
- this bit set, then opening /dev/watchdog will skip the start operation)
+ is active or not from user perspective. User space is expected to send
+ heartbeat requests to the driver while this flag is set.
* WDOG_NO_WAY_OUT: this bit stores the nowayout setting for the watchdog.
If this bit is set then the watchdog timer will not be able to stop.
+* WDOG_HW_RUNNING: Set by the watchdog driver if the hardware watchdog is
+ running. The bit must be set if the watchdog timer hardware can not be
+ stopped. The bit may also be set if the watchdog timer is running after
+ booting, before the watchdog device is opened. If set, the watchdog
+ infrastructure will send keepalives to the watchdog hardware while
+ WDOG_ACTIVE is not set.
+ Note: when you register the watchdog timer device with this bit set,
+ then opening /dev/watchdog will skip the start operation but send a keepalive
+ request instead.
To set the WDOG_NO_WAY_OUT status bit (before registering your watchdog
timer device) you can either:
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