Hi Markus, > Many watchdog driver reset the watchdog device on initialization. This > is a problem if the watchdog is activated by the bootloader and should > be active the whole time until the userspace can write to it. > > This patch adds a module parameter (watchdog.activate_first) that > activates the first registered watchdog. Using this parameter it is > possible to have an active watchdog during the whole boot process. > > Signed-off-by: Markus Pargmann <mpa@xxxxxxxxxxxxxx> NAK. It is the responsibility of the watchdog device driver to do this and not that of the core. The core can't know which device(s) are running and can't be turned off. So you can have more then 1 device that needs to keep going... The normal way do this is by using a timer. Take a look at at91sam9_wdt.c . We have a timer there that pings the watchdog if 1) the watchdog device is not active for userspace (so before opening /dev/watchdog and after clossing /dev/watchdog correctly) 2) pings 1/2 or 1/4 of the watchdog heartbeat time as long as the userspace ping keeps going. (Else it will expire and you trigger a reboot). (Note: the heartbeat is the period after which a watchdog hardware device will trigger a reboot, timeout is the period for userspace. So for most devices heartbeat and timeout are the same, but for devices where a timer is used (we also use it if the heartbeat value is too small (i.e. 1 second)) the values have a different meaning.) So the logic for a watchdog device driver is: at startup the watchdog device driver should make sure that a reboot can only occur when /dev/watchdog is open. This means that if a watchdog device is active at boot it should either be stopped (that's why most drivers have a stop in their init/probe function) or have a timer that pings the watchdog as long as it is not active for userspace (like at91sam9_wdt.c, via_wdt.c, pika_wdt.c, ...) Kind regards, Wim. -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
