wdt - ICS PCI-WDT500/501 watchdog timer device driver
wdt0 at pci? dev ? function ?
The wdt driver provides support for the Industrial Computer
and PCI-WDT501 boards.
For PCI-WDT500 boards, basic watchdog timer functionality is
For PCI-WDT501 boards, additional access to the onboard
inputs, temperature, and power supply monitors is provided.
the onboard buzzer on PCI-WDT501 boards, add option
your kernel configuration.
By default the watchdog timer is set to 30 seconds and is
the kernel's timeout processing. If the kernel crashes, the
timer is not reset and the system will reboot (assuming a
is made between the WDT50x and motherboard). Alternatively, the
watchdog can be reinitialized via a userland process which
process scheduling, not just kernel timeout processing, is
place. See the WIOCSCHED ioctl(2) below for more information.
The wdt driver is controlled via ioctl(2) calls to
/dev/wdt0. The following
commands are supported:
WIOCGETSTATE Returns the current temperature and board status into the
wdt_state structure pointer passed to
<dev/pci/wdt50x.h> for the definition of the
structure and state bits.
WIOCSCHED Places the process into an infinite loop (interrupted only
via a signal) to guarantee process scheduling.
utilizes the process' context to reinitialize
timeout. Should process scheduling fail, the
not be reinitialized and the system will be
that it is possible to force a reboot by sending a SIGSTOP
signal to a process in WIOCSCHED and waiting
for the watchdog
timer to expire. Since WIOCSCHED can have
consequences, it may only be issued by superuser processes
regardless of the permissions on
/dev/wdt0 watchdog control device
/usr/include/dev/pci/wdt50x.h structure and ioctl definitions
ioctl(2), intro(4), pci(4)
The wdt driver first appeared in OpenBSD 2.6.
The ioctl interface isn't generic.
It's unwise to combine wdt with ddb(4) since the latter may
former from resetting the watchdog timeout before it expires.
OpenBSD 3.6 April 25, 1999
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