Watchdog

Collaboration diagram for Watchdog:

Macros
#define	HW_WATCHDOG_DEFAULT_DEVICE   "/dev/watchdog0"
	Default device path used by hw_watchdog_init(). More...

Typedefs
typedef struct hw_watchdog_t	hw_watchdog_t
	Watchdog adapter handle.

Functions
hw_watchdog_t *	hw_watchdog_init (void)
	Initialize the watchdog singleton. More...
hw_watchdog_t *	hw_watchdog_init_device (const char *device)
	Initialize the watchdog singleton for a specific device path. More...
void	hw_watchdog_deinit (hw_watchdog_t *watchdog)
	Deinitialize the watchdog singleton. More...
uint32_t	hw_watchdog_maxtimeout_ms (void)
	Return the maximum supported watchdog timeout in milliseconds. More...
bool	hw_watchdog_did_reset (hw_watchdog_t *watchdog)
	Report whether the last reboot/reset was caused by the watchdog. More...
void	hw_watchdog_enable (hw_watchdog_t *watchdog, bool enable)
	Enable or disable watchdog feeding mode. More...
void	hw_watchdog_reset (hw_watchdog_t *watchdog, uint32_t delay_ms)
	Trigger a delayed device reset (reboot). More...

Detailed Description

The watchdog module provides a singleton watchdog adapter that can detect a stalled application and can also trigger a delayed reset programmatically.

After enabling the watchdog, applications should call hw_poll() regularly so the watchdog can be fed. If feeding stops for longer than the supported timeout, the backend triggers a reset action.

hw_watchdog_reset() arms a delayed device reset (a reboot) without requiring additional polling. The pending reset can be cancelled by calling hw_watchdog_enable().

Note

Unlike I2C/SPI/PWM, Raspberry Pi OS's hardware watchdog (bcm2835_wdt) is commonly already active out of the box - /dev/watchdog and /dev/watchdog0 exist and already counting down with no config.txt change (wdctl shows its current timeout/time left). If it's ever not already active, dtparam=watchdog=on in config.txt is the documented way to force it on, needing a reboot to take effect.

Macro Definition Documentation

HW_WATCHDOG_DEFAULT_DEVICE

#define HW_WATCHDOG_DEFAULT_DEVICE   "/dev/watchdog0"

Default device path used by hw_watchdog_init().

/dev/watchdog0, not the legacy un-numbered /dev/watchdog misc device - see hw_watchdog_init_device()'s own doc on the difference. Override by defining HW_WATCHDOG_DEFAULT_DEVICE at compile time.

Definition at line 46 of file watchdog.h.

Function Documentation

hw_watchdog_deinit()

void hw_watchdog_deinit

(

hw_watchdog_t *

watchdog

)

Deinitialize the watchdog singleton.

Parameters

watchdog

Watchdog handle.

Deinitialization also disables any active watchdog feeding or pending reset behavior before releasing backend resources.

hw_watchdog_did_reset()

bool hw_watchdog_did_reset

(

hw_watchdog_t *

watchdog

)

Report whether the last reboot/reset was caused by the watchdog.

Parameters

watchdog

Watchdog handle.

Return values

true	Previous reboot/reset was watchdog-driven.
false	Previous reboot/reset was not watchdog-driven or unsupported.

hw_watchdog_enable()

void hw_watchdog_enable	(	hw_watchdog_t *	watchdog,
		bool	enable
	)

Enable or disable watchdog feeding mode.

Parameters

watchdog	Watchdog handle.
enable	When true, enable watchdog feeding mode. When false, disable watchdog activity.

Enabling watchdog feeding mode expects callers to invoke hw_poll() often enough to refresh the watchdog before timeout.

hw_watchdog_init()

hw_watchdog_t* hw_watchdog_init

(

void

)

Initialize the watchdog singleton.

Returns

Singleton watchdog handle, or NULL when unsupported.

hw_watchdog_init_device()

hw_watchdog_t* hw_watchdog_init_device

(

const char *

device

)

Initialize the watchdog singleton for a specific device path.

Parameters

device

Device path or identifier to open.

Returns

Singleton watchdog handle, or NULL when unsupported.

This is intended for backends that expose multiple watchdog devices, such as Linux /dev/watchdog0, /dev/watchdog1, etc. (one per registered kernel watchdog driver) - as opposed to /dev/watchdog, an older, un-numbered device path kept only for backward compatibility, aliased to whichever watchdog driver registered first.

hw_watchdog_maxtimeout_ms()

uint32_t hw_watchdog_maxtimeout_ms

(

void

)

Return the maximum supported watchdog timeout in milliseconds.

Returns

Maximum supported timeout in milliseconds, or 0 when unsupported.

hw_watchdog_reset()

void hw_watchdog_reset	(	hw_watchdog_t *	watchdog,
		uint32_t	delay_ms
	)

Trigger a delayed device reset (reboot).

Parameters

watchdog	Watchdog handle.
delay_ms	Delay in milliseconds before the device resets.

The delay is clamped to hw_watchdog_maxtimeout_ms(). A pending reset can be cancelled by calling hw_watchdog_enable().