WDT(4) OpenBSD Programmer's Manual (i386) WDT(4)
NAME
wdt - ICS PCI-WDT500/501 watchdog timer device driver
SYNOPSIS
wdt0 at pci?
option WDT_DISABLE_BUZZER
DESCRIPTION
The wdt driver provides support for the Industrial Computer Source PCI-
WDT500 and PCI-WDT501 boards.
For PCI-WDT500 boards, basic watchdog timer functionality is supported.
For PCI-WDT501 boards, additional access to the onboard buzzer, isolated
inputs, temperature, and power supply monitors is provided. To disable
the onboard buzzer on PCI-WDT501 boards, add option WDT_DISABLE_BUZZER to
your kernel configuration.
By default the watchdog timer is set to 30 seconds and is refreshed by
the kernel's timeout processing. If the kernel crashes, the watchdog
timer is not reset and the system will reboot (assuming a proper connec-
tion is made between the WDT50x and motherboard). Alternatively, the
watchdog can be reinitialized via a userland process which ensures that
process scheduling, not just kernel timeout processing, is still taking
place. See the WIOCSCHED ioctl(2) below for more information.
INTERFACE
The wdt driver is controlled via ioctl(2) calls to /dev/wdt0. The fol-
lowing commands are supported:
WIOCGETSTATE Returns the current temperature and board status into the
wdt_state structure pointer passed to ioctl(2). See
<dev/pci/wdt50x.h> for the definition of the wdt_state
structure and state bits.
WIOCSCHED Places the process into an infinite loop (interrupted only
via a signal) to guarantee process scheduling. The driver
utilizes the process' context to reinitialize the watchdog
timeout. Should process scheduling fail, the timeout will
not be reinitialized and the system will be rebooted. Note
that it is possible to force a reboot by sending a SIGSTOP
signal to a process in WIOCSCHED and waiting for the watch-
dog timer to expire. Since WIOCSCHED can have such dramat-
ic consequences, it may only be issued by superuser pro-
cesses regardless of the permissions on /dev/wdt0.
FILES
/dev/wdt0 watchdog control device
/usr/include/dev/pci/wdt50x.h structure and ioctl definitions
SEE ALSO
ioctl(2), intro(4), pci(4), watchdog(4)
HISTORY
The wdt driver first appeared in OpenBSD 2.6.
BUGS
The ioctl interface isn't generic.
It's unwise to combine wdt with ddb(4), since the latter may prevent the
former from resetting the watchdog timeout before it expires.
OpenBSD 3.9 April 25, 1999 1