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Diffstat (limited to 'share/man/man4/watchdog.4')
-rw-r--r-- | share/man/man4/watchdog.4 | 94 |
1 files changed, 69 insertions, 25 deletions
diff --git a/share/man/man4/watchdog.4 b/share/man/man4/watchdog.4 index a533ec8..c0887fa 100644 --- a/share/man/man4/watchdog.4 +++ b/share/man/man4/watchdog.4 @@ -32,54 +32,95 @@ .Nm watchdog .Nd "hardware and software watchdog" .Sh SYNOPSIS -.Cd "options CPU_ELAN" -.Cd "options CPU_GEODE" -.Cd "options SW_WATCHDOG" -.Pp .In sys/watchdog.h .Sh DESCRIPTION The .Nm facility is used for controlling hardware and software watchdogs. .Pp -The interface is through a device .Pa /dev/fido -which responds to a single +responds to a single .Xr ioctl 2 call, .Dv 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. .Pp -The call takes a single argument which represents a timeout value -specified as an integer power of two nanoseconds. -.Pp -The .Dv WD_ACTIVE -flag signals that the +indicates that the .Nm -will be kept from -timing out from userland, for instance by the +will be kept from timing out from userland, for instance by the .Xr watchdogd 8 daemon. -.Pp -To disable the watchdogs, an argument of zero should be used. +.Dv WD_PASSIVE +indicates that the +.Nm +will be kept from timing out from the kernel. .Pp The .Xr ioctl 2 call will return success if just one of the available .Xr watchdog 9 -implementations support the request. -If the call fails, for instance if none of +implementations supports setting the timeout to the specified timeout. This +means that at least one watchdog is armed. If the call fails, for instance if +none of .Xr watchdog 9 -implementations support the timeout -length, all watchdogs are disabled and must be explicitly re-enabled. +implementations support the timeout length, all watchdogs are disabled and must +be explicitly re-enabled. +.Pp +To disable the watchdogs pass +.Dv WD_TO_NEVER . +If disarming the watchdog(s) failed an error is returned. The watchdog might +still be armed! +.Sh RETURN VALUES +The ioctl returns zero on success and non-zero on failure. +.Bl -tag -width Er +.It Bq Er EOPNOTSUPP +No watchdog present in the kernel (timeout value other than 0). +.It Bq Er EOPNOTSUPP +Watchdog could not be disabled (timeout value of 0). +.It Bq Er EINVALID +Invalid flag combination passed. +.It Bq Er EINVALID +None of the watchdogs supports the requested timeout value. .Sh EXAMPLES -.\" XXX insert some descriptive text here .Bd -literal -offset indent -u_int u = WD_ACTIVE | WD_TO_8SEC; -int fd = open("/dev/fido", O_RDWR); +#include <paths.h> +#include <sys/watchdog.h> + +#define WDPATH "/dev/" _PATH_WATCHDOG +int wdfd = -1; -ioctl(fd, WDIOCPATPAT, &u); +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); .Ed +.Pp +Enables a watchdog to recover from a potentially freezing piece of code. +.Pp +.Bd -literal -offset indent +options SW_WATCHDOG +.Ed +.Pp +in your kernel config adds a software watchdog in the kernel, dropping to KDB +or panic-ing when firing. .Sh SEE ALSO .Xr watchdogd 8 , .Xr watchdog 9 @@ -88,14 +129,17 @@ The .Nm code first appeared in .Fx 5.1 . +.Sh BUGS +The +.Dv WD_PASSIVE +option has not yet been implemented. .Sh AUTHORS .An -nosplit The .Nm facility was written by .An Poul-Henning Kamp Aq phk@FreeBSD.org . -The software watchdog code -and this manual page were written by +The software watchdog code and this manual page were written by .An Sean Kelly Aq smkelly@FreeBSD.org . Some contributions were made by .An Jeff Roberson Aq jeff@FreeBSD.org . |