Name
kfifo_put — 
     put data into the fifo
 
Arguments
- fifo
- 
     address of the fifo to be used
     
- val
- 
     the data to be added
     
Description
   This macro copies the given value into the fifo.
   It returns 0 if the fifo was full. Otherwise it returns the number
   processed elements.
   
   Note that with only one concurrent reader and one concurrent
   writer, you don't need extra locking to use these macro.