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DESCRIPTION

The device /dev/fido supports several optional ioctl(2) calls for configuration, and responds to a single operational ioctl call, WDIOCPATPAT. It takes a single argument which represents a timeout value specified as a power of two nanoseconds, or-ed with a flag selecting active or passive control of the watchdog.

WD_ACTIVE indicates that the watchdog will be kept from timing out from userland, for instance by the watchdogd(8) daemon. WD_PASSIVE indicates that the watchdog will be kept from timing out from the kernel.

The WDIOCPATPAT ioctl(2) call will return success if just one of the available watchdog(9) implementations supports setting the timeout to the specified timeout. This means that at least one watchdog is armed. By default, this will be a hardware watchdog if one is present, but if no hardware watchdog is able to process the request, a default software watchdog is enabled. If the call fails, for instance if none of watchdog(9) implementations support the timeout length, all watchdogs are disabled and must be explicitly re-enabled.

To disable the watchdogs pass WD_TO_NEVER. If disarming the watchdog(s) failed an error is returned. The watchdog might still be armed!

The optional configuration ioctl commands are listed here, along with the type of the parameter used. Examples of their use can be found in watchdogd(8).

WDIOC_SETTIMEOUT int

set/reset the timer

WDIOC_GETTIMEOUT int

get total timeout

WDIOC_GETTIMELEFT int

get time left

WDIOC_GETPRETIMEOUT int

get the pre-timeout

WDIOC_SETPRETIMEOUT int

set the pre-timeout

WDIOC_SETPRETIMEOUTACT int

Set the action when a pre-timeout occurs (see WD_SOFT_* below).

WDIOC_SETSOFT int

Use an internal software watchdog instead of hardware. There is also an external software watchdog, which is used by default if no hardware watchdog was attached.

WDIOC_SETSOFTTIMEOUTACT int

Set the action whan a soft timeout occurs.

The actions that may be specified for the pre-timeout or the internal software watchdog are listed here. Multiple actions can be specified by ORing values together.

WD_SOFT_PANIC

panic

WD_SOFT_DDB

enter debugger

WD_SOFT_LOG

log(9)

WD_SOFT_PRINT

printf(9)

#include <paths.h>
#include <sys/watchdog.h>

#define WDPATH	"/dev/" _PATH_WATCHDOG
int wdfd = -1;

static void
wd_init(void)
{
	wdfd = open(WDPATH, O_RDWR);
	if (wdfd == -1)
		err(1, WDPATH);
}
static void
wd_reset(u_int timeout)
{
	if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1)
		err(1, "WDIOCPATPAT");
}

/* in main() */
wd_init();
wd_reset(WD_ACTIVE|WD_TO_8SEC);
/* potential freeze point */
wd_reset(WD_TO_NEVER);