diff --git a/[refs] b/[refs]
index 0a92678e20d2..596bafcc65d9 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8d4be669479d95a0c6eb4b6a538460f0ab35c4f7
+refs/heads/master: d21af4cbfb7fccbccedc1d9e143a14aee6b1c9ad
diff --git a/trunk/drivers/staging/comedi/comedi_buf.c b/trunk/drivers/staging/comedi/comedi_buf.c
index 95cbe365ded2..fd2a92e29fb0 100644
--- a/trunk/drivers/staging/comedi/comedi_buf.c
+++ b/trunk/drivers/staging/comedi/comedi_buf.c
@@ -252,11 +252,12 @@ static unsigned int comedi_buf_munge(struct comedi_async *async,
 /* transfers a chunk from writer to filled buffer space */
 unsigned comedi_buf_write_free(struct comedi_async *async, unsigned int nbytes)
 {
-	if ((int)(async->buf_write_count + nbytes -
-		  async->buf_write_alloc_count) > 0) {
+	unsigned int allocated = comedi_buf_write_n_allocated(async);
+
+	if (nbytes > allocated) {
 		dev_info(async->subdevice->device->class_dev,
 			 "attempted to write-free more bytes than have been write-allocated.\n");
-		nbytes = async->buf_write_alloc_count - async->buf_write_count;
+		nbytes = allocated;
 	}
 	async->buf_write_count += nbytes;
 	async->buf_write_ptr += nbytes;