1.\" Copyright (c) 2004 Poul-Henning Kamp <phk@FreeBSD.org> 2.\" Copyright (c) 2003, 2004 Sean M. Kelly <smkelly@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd June 25, 2003 29.Dt WATCHDOG 4 30.Os 31.Sh NAME 32.Nm watchdog 33.Nd "hardware and software watchdog" 34.Sh SYNOPSIS 35.In sys/watchdog.h 36.Sh DESCRIPTION 37The 38.Nm 39facility is used for controlling hardware and software watchdogs. 40.Pp 41.Pa /dev/fido 42responds to a single 43.Xr ioctl 2 44call, 45.Dv WDIOCPATPAT . 46It takes a single argument which represents a timeout value specified as a 47power of two nanoseconds, or-ed with a flag selecting active or passive control 48of the watchdog. 49.Pp 50.Dv WD_ACTIVE 51indicates that the 52.Nm 53will be kept from timing out from userland, for instance by the 54.Xr watchdogd 8 55daemon. 56.Dv WD_PASSIVE 57indicates that the 58.Nm 59will be kept from timing out from the kernel. 60.Pp 61The 62.Xr ioctl 2 63call will return success if just one of the available 64.Xr watchdog 9 65implementations supports setting the timeout to the specified timeout. This 66means that at least one watchdog is armed. If the call fails, for instance if 67none of 68.Xr watchdog 9 69implementations support the timeout length, all watchdogs are disabled and must 70be explicitly re-enabled. 71.Pp 72To disable the watchdogs pass 73.Dv WD_TO_NEVER . 74If disarming the watchdog(s) failed an error is returned. The watchdog might 75still be armed! 76.Sh RETURN VALUES 77The ioctl returns zero on success and non-zero on failure. 78.Bl -tag -width Er 79.It Bq Er EOPNOTSUPP 80No watchdog present in the kernel (timeout value other than 0). 81.It Bq Er EOPNOTSUPP 82Watchdog could not be disabled (timeout value of 0). 83.It Bq Er EINVALID 84Invalid flag combination passed. 85.It Bq Er EINVALID 86None of the watchdogs supports the requested timeout value. 87.El 88.Sh EXAMPLES 89.Bd -literal -offset indent 90#include <paths.h> 91#include <sys/watchdog.h> 92 93#define WDPATH "/dev/" _PATH_WATCHDOG 94int wdfd = -1; 95 96static void 97wd_init(void) 98{ 99 wdfd = open(WDPATH, O_RDWR); 100 if (wdfd == -1) 101 err(1, WDPATH); 102} 103static void 104wd_reset(u_int timeout) 105{ 106 if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1) 107 err(1, "WDIOCPATPAT"); 108} 109 110/* in main() */ 111wd_init(); 112wd_reset(WD_ACTIVE|WD_TO_8SEC); 113/* potential freeze point */ 114wd_reset(WD_TO_NEVER); 115.Ed 116.Pp 117Enables a watchdog to recover from a potentially freezing piece of code. 118.Pp 119.Bd -literal -offset indent 120options SW_WATCHDOG 121.Ed 122.Pp 123in your kernel config adds a software watchdog in the kernel, dropping to KDB 124or panic-ing when firing. 125.Sh SEE ALSO 126.Xr watchdogd 8 , 127.Xr watchdog 9 128.Sh HISTORY 129The 130.Nm 131code first appeared in 132.Fx 5.1 . 133.Sh BUGS 134The 135.Dv WD_PASSIVE 136option has not yet been implemented. 137.Sh AUTHORS 138.An -nosplit 139The 140.Nm 141facility was written by 142.An Poul-Henning Kamp Aq phk@FreeBSD.org . 143The software watchdog code and this manual page were written by 144.An Sean Kelly Aq smkelly@FreeBSD.org . 145Some contributions were made by 146.An Jeff Roberson Aq jeff@FreeBSD.org . 147