[PATCH 10/11] staging: comedi: comedi_buf: clarify comedi_buf_read_alloc()

[H Hartley Sweeten]

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

Also, cleanup the multi-line comment about the barrier.

Signed-off-by: H Hartley Sweeten <hsweeten at visionengravers.com>
Cc: Ian Abbott <abbobbi at mev.co.uk>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 drivers/staging/comedi/comedi_buf.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
index a12b70b..a95bb3d 100644
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/drivers/staging/comedi/comedi_buf.c
@@ -293,14 +293,19 @@ 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 = 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 */
+
+	/*
+	 * barrier insures the read of munge_count above occurs
+	 * before any following reads out of the buffer
+	 */
 	smp_rmb();
+
 	return nbytes;
 }
 EXPORT_SYMBOL(comedi_buf_read_alloc);
-- 
1.8.0