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Commit 3abfa106 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: comedi_buf: clarify comedi_buf_read_free() 



Reword the comment about the need for the smp_mb().

Clarify the check to make sure the number of bytes to free is not
more than the number of bytes allocated.

Signed-off-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 034cbd17

drivers/staging/comedi/comedi_buf.c

+10 −5
Original line number Diff line number Diff line
@@ -312,14 +312,19 @@ EXPORT_SYMBOL(comedi_buf_read_alloc); 
/* transfers control of a chunk from reader to free buffer space */

unsigned comedi_buf_read_free(struct comedi_async *async, unsigned int nbytes)

{

	/* barrier insures data has been read out of

	 * buffer before read count is incremented */

	unsigned int allocated;



	/*

	 * ensure data has been read out of buffer before

	 * the async read count is incremented

	 */

	smp_mb();

	if ((int)(async->buf_read_count + nbytes -

		  async->buf_read_alloc_count) > 0) {



	allocated = comedi_buf_read_n_allocated(async);

	if (nbytes > allocated) {

		dev_info(async->subdevice->device->class_dev,

			 "attempted to read-free more bytes than have been read-allocated.\n");

		nbytes = async->buf_read_alloc_count - async->buf_read_count;

		nbytes = allocated;

	}

	async->buf_read_count += nbytes;

	async->buf_read_ptr += nbytes;