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NAME    [Toc]    [Back]

     wdt - ICS PCI-WDT500/501 watchdog timer device driver

SYNOPSIS    [Toc]    [Back]

     wdt0 at pci? dev ? function ?

DESCRIPTION    [Toc]    [Back]

     The wdt driver provides support for the Industrial  Computer
Source PCIWDT500
 and PCI-WDT501 boards.

     For PCI-WDT500 boards, basic watchdog timer functionality is
     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
     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
     timer  is  not  reset and the system will reboot (assuming a
proper connection
 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    [Toc]    [Back]

     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
ioctl(2).  See
                   <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.
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 watchdog
 timer to expire.  Since WIOCSCHED can have
such dramatic
 consequences, it may only be issued by  superuser processes
   regardless   of  the  permissions  on

FILES    [Toc]    [Back]

     /dev/wdt0                      watchdog control device
     /usr/include/dev/pci/wdt50x.h  structure and  ioctl  definitions

SEE ALSO    [Toc]    [Back]

     ioctl(2), intro(4), pci(4)

HISTORY    [Toc]    [Back]

     The wdt driver first appeared in OpenBSD 2.6.

BUGS    [Toc]    [Back]

     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      3.6                          April      25,     1999
[ Back ]
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