- kfifo_to_user(fifo, to, len, copied);
- address of the fifo to be used
- where the data must be copied
- the size of the destination buffer
- pointer to output variable to store the number of copied bytes
This macro copies at most len bytes from the fifo into the to buffer and returns -EFAULT/0.
Note that with only one concurrent reader and one concurrent writer, you don't need extra locking to use these macro.