Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 034cbd17 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
Browse files

staging: comedi: comedi_buf: clarify comedi_buf_read_alloc() 



Clarify the check to make sure the number of bytes to allocate is
available.

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

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 43f9137d

drivers/staging/comedi/comedi_buf.c

+12 −6
Original line number Diff line number Diff line
@@ -291,14 +291,20 @@ EXPORT_SYMBOL(comedi_buf_read_n_available); 
/* allocates a chunk for the reader from filled (and munged) buffer space */

unsigned comedi_buf_read_alloc(struct comedi_async *async, unsigned nbytes)

{

	if ((int)(async->buf_read_alloc_count + nbytes - async->munge_count) >

	    0) {

		nbytes = async->munge_count - async->buf_read_alloc_count;

	}

	unsigned int available;



	available = async->munge_count - async->buf_read_alloc_count;

	if (nbytes > available)

		nbytes = available;



	async->buf_read_alloc_count += nbytes;

	/* barrier insures read of munge_count occurs before we actually read

	   data out of buffer */



	/*

	 * ensure the async buffer 'counts' are read before we

	 * attempt to read data from the read-alloc'ed buffer space

	 */

	smp_rmb();



	return nbytes;

}

EXPORT_SYMBOL(comedi_buf_read_alloc);