__kfifo_put — puts some data into the FIFO, no locking version
the fifo to be used.
the data to be added.
the length of the data to be added.
This function copies at most len bytes from the buffer into the FIFO depending on the free space, and returns the number of bytes copied.
Note that with only one concurrent reader and one concurrent writer, you don't need extra locking to use these functions.