diff options
Diffstat (limited to 'Documentation/watchdog')
| -rw-r--r-- | Documentation/watchdog/watchdog-kernel-api.txt | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt index 15a02595ade1..954134a5c4a4 100644 --- a/Documentation/watchdog/watchdog-kernel-api.txt +++ b/Documentation/watchdog/watchdog-kernel-api.txt @@ -137,10 +137,10 @@ are: * stop: with this routine the watchdog timer device is being stopped. The routine needs a pointer to the watchdog timer device structure as a parameter. It returns zero on success or a negative errno code for failure. - Some watchdog timer hardware can only be started and not be stopped. The - driver supporting this hardware needs to make sure that a start and stop - routine is being provided. This can be done by using a timer in the driver - that regularly sends a keepalive ping to the watchdog timer hardware. + Some watchdog timer hardware can only be started and not be stopped. + If a watchdog can not be stopped, the watchdog driver must set the + WDOG_HW_RUNNING flag in its stop function to inform the watchdog core that + the watchdog is still running. Not all watchdog timer hardware supports the same functionality. That's why all other routines/operations are optional. They only need to be provided if @@ -189,11 +189,19 @@ The 'ref' and 'unref' operations are no longer used and deprecated. The status bits should (preferably) be set with the set_bit and clear_bit alike bit-operations. The status bits that are defined are: * WDOG_ACTIVE: this status bit indicates whether or not a watchdog timer device - is active or not. When the watchdog is active after booting, then you should - set this status bit (Note: when you register the watchdog timer device with - this bit set, then opening /dev/watchdog will skip the start operation) + is active or not from user perspective. User space is expected to send + heartbeat requests to the driver while this flag is set. * WDOG_NO_WAY_OUT: this bit stores the nowayout setting for the watchdog. If this bit is set then the watchdog timer will not be able to stop. +* WDOG_HW_RUNNING: Set by the watchdog driver if the hardware watchdog is + running. The bit must be set if the watchdog timer hardware can not be + stopped. The bit may also be set if the watchdog timer is running after + booting, before the watchdog device is opened. If set, the watchdog + infrastructure will send keepalives to the watchdog hardware while + WDOG_ACTIVE is not set. + Note: when you register the watchdog timer device with this bit set, + then opening /dev/watchdog will skip the start operation but send a keepalive + request instead. To set the WDOG_NO_WAY_OUT status bit (before registering your watchdog timer device) you can either: |