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.Sh EXAMPLES 88.Bd -literal -offset indent 89#include <paths.h> 90#include <sys/watchdog.h> 91 92#define WDPATH "/dev/" _PATH_WATCHDOG 93int wdfd = -1; 94 95static void 96wd_init(void) 97{ 98 wdfd = open(WDPATH, O_RDWR); 99 if (wdfd == -1) 100 err(1, WDPATH); 101} 102static void 103wd_reset(u_int timeout) 104{ 105 if (ioctl(wdfd, WDIOCPATPAT, &timeout) == -1) 106 err(1, "WDIOCPATPAT"); 107} 108 109/* in main() */ 110wd_init(); 111wd_reset(WD_ACTIVE|WD_TO_8SEC); 112/* potential freeze point */ 113wd_reset(WD_TO_NEVER); 114.Ed 115.Pp 116Enables a watchdog to recover from a potentially freezing piece of code. 117.Pp 118.Bd -literal -offset indent 119options SW_WATCHDOG 120.Ed 121.Pp 122in your kernel config adds a software watchdog in the kernel, dropping to KDB 123or panic-ing when firing. 124.Sh SEE ALSO 125.Xr watchdogd 8 , 126.Xr watchdog 9 127.Sh HISTORY 128The 129.Nm 130code first appeared in 131.Fx 5.1 . 132.Sh BUGS 133The 134.Dv WD_PASSIVE 135option has not yet been implemented. 136.Sh AUTHORS 137.An -nosplit 138The 139.Nm 140facility was written by 141.An Poul-Henning Kamp Aq phk@FreeBSD.org . 142The software watchdog code and this manual page were written by 143.An Sean Kelly Aq smkelly@FreeBSD.org . 144Some contributions were made by 145.An Jeff Roberson Aq jeff@FreeBSD.org . 146