From: gleb@nbase.co.il (Gleb Natapov)

There is inconsistency in fops->write() implementation in different
watchdog drivers.  Some of them return number of bytes written while others
return 1.

I think the correct implementation should always return number of bytes
written (we examine all the buffer after all) otherwise "echo V >
/dev/watchdog" doesn't work as expected (it doesn't stop watchdog).