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Commit a5b9e2c1 authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
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kfifo: add kfifo_out_peek 



In some upcoming code it's useful to peek into a FIFO without permanentely
removing data.  This patch implements a new kfifo_out_peek() to do this.

Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
Acked-by: default avatarStefani Seibold <stefani@seibold.net>
Cc: Roland Dreier <rdreier@cisco.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Andy Walls <awalls@radix.net>
Cc: Vikram Dhillon <dhillonv10@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 64ce1037

include/linux/kfifo.h

+3 −0
Original line number Diff line number Diff line
@@ -113,6 +113,9 @@ extern unsigned int kfifo_in(struct kfifo *fifo, 
				const void *from, unsigned int len);

extern __must_check unsigned int kfifo_out(struct kfifo *fifo,

				void *to, unsigned int len);

extern __must_check unsigned int kfifo_out_peek(struct kfifo *fifo,

				void *to, unsigned int len, unsigned offset);





/**

 * kfifo_reset - removes the entire FIFO contents

kernel/kfifo.c

+21 −0
Original line number Diff line number Diff line
@@ -302,6 +302,27 @@ unsigned int kfifo_out(struct kfifo *fifo, void *to, unsigned int len) 
}

EXPORT_SYMBOL(kfifo_out);



/**

 * kfifo_out_peek - copy some data from the FIFO, but do not remove it

 * @fifo: the fifo to be used.

 * @to: where the data must be copied.

 * @len: the size of the destination buffer.

 * @offset: offset into the fifo

 *

 * This function copies at most @len bytes at @offset from the FIFO

 * into the @to buffer and returns the number of copied bytes.

 * The data is not removed from the FIFO.

 */

unsigned int kfifo_out_peek(struct kfifo *fifo, void *to, unsigned int len,

			    unsigned offset)

{

	len = min(kfifo_len(fifo), len + offset);



	__kfifo_out_data(fifo, to, len, offset);

	return len;

}

EXPORT_SYMBOL(kfifo_out_peek);



unsigned int __kfifo_out_generic(struct kfifo *fifo,

	void *to, unsigned int len, unsigned int recsize,

	unsigned int *total)