rtf_create_rt_handler installs a handler which is executed when rtf_put or rtf_get is called on the specified real-time fifo (RT-FIFO). fifo is an RT-FIFO that must have previously been created with a call to rtf_create. handler is then called whenever that fifo is accessed in RT mode.
Note that the handler is called in the context of the task that uses rtf_put or rtf_get. You can use semaphores to take handler actions asynchronously: use sem_wait(3) in a thread, and post the semaphore from the handler.
The RT-FIFO is a mechanism, implemented as a character device, to communicate between realtime software components (either in threads or handlers), and between realtime software and ordinary Linux processes. The rtf_* functions are used in RT mode; Linux processes use standard character device access functions, such as read(2), write(2) and select(2).
fifo is greater than or equal to RTF_NO, or is not a valid RT-FIFO identifier; or handler is NULL.