Man page 9 : kfifo_out_spinlocked

kfifo_out_spinlocked - get data from the fifo using a spinlock for locking

kfifo_out_spinlocked( fifo , buf , n , lock );

fifo
    address of the fifo to be used

buf
    pointer to the storage buffer

n
    max. number of elements to get

lock
    pointer to the spinlock to use for locking

This macro get the data from the fifo and return the numbers of elements copied.