[PATCH 08/11] staging: comedi: comedi_buf: clarify comedi_buf_read_free()

H Hartley Sweeten hsweeten at visionengravers.com
Fri Dec 21 16:41:50 UTC 2012


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

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 | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
index 5e08266..246f577 100644
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/drivers/staging/comedi/comedi_buf.c
@@ -313,14 +313,16 @@ 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)
 {
+	unsigned allocated;
+
 	/* barrier insures data has been read out of
 	 * buffer before 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;
-- 
1.8.0




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