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docs: watchdog-kernel-api: general cleanups

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Fix grammar and punctuation.
Add a missing struct member (pm_nb) and its description.
Add a subheading for Helper Functions between the struct descriptions
and just pure helper functions.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20260228010402.2389343-5-rdunlap@infradead.org>
This commit is contained in:
Randy Dunlap 2026-02-27 17:04:01 -08:00 committed by Jonathan Corbet
parent 2a64c824d0
commit bb227ba68c
1 changed files with 13 additions and 7 deletions
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20
Documentation/watchdog/watchdog-kernel-api.rst
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@ -38,8 +38,8 @@ The watchdog_unregister_device routine deregisters a registered watchdog timer
device. The parameter of this routine is the pointer to the registered
watchdog_device structure.
The watchdog subsystem includes an registration deferral mechanism,
which allows you to register an watchdog as early as you wish during
The watchdog subsystem includes a registration deferral mechanism,
which allows you to register a watchdog as early as you wish during
the boot process.
The watchdog device structure looks like this::
@ -60,13 +60,14 @@ The watchdog device structure looks like this::
unsigned int max_hw_heartbeat_ms;
struct notifier_block reboot_nb;
struct notifier_block restart_nb;
struct notifier_block pm_nb;
void *driver_data;
struct watchdog_core_data *wd_data;
unsigned long status;
struct list_head deferred;
};
It contains following fields:
It contains the following fields:
* id: set by watchdog_register_device, id 0 is special. It has both a
/dev/watchdog0 cdev (dynamic major, minor 0) as well as the old
@ -105,6 +106,8 @@ It contains following fields:
internal use only. If a watchdog is capable of restarting the machine, it
should define ops->restart. Priority can be changed through
watchdog_set_restart_priority.
* pm_nb: coordinates watchdog_dev_suspend/resume to cancel a ping worker
during suspend and restore it during resume.
* bootstatus: status of the device after booting (reported with watchdog
WDIOF_* status bits).
* driver_data: a pointer to the drivers private data of a watchdog device.
@ -204,7 +207,7 @@ they are supported. These optional routines/operations are:
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
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.
@ -220,7 +223,7 @@ they are supported. These optional routines/operations are:
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).
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
@ -239,7 +242,7 @@ they are supported. These optional routines/operations are:
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
* WDOG_ACTIVE: this status bit indicates whether a watchdog timer device
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.
@ -254,6 +257,9 @@ bit-operations. The status bits that are defined are:
then opening /dev/watchdog will skip the start operation but send a keepalive
request instead.
Helper Functions
~~~~~~~~~~~~~~~~
To set the WDOG_NO_WAY_OUT status bit (before registering your watchdog
timer device) you can either:
@ -331,7 +337,7 @@ 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,
governor framework (kconfig 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