staging: comedi: comedi_buf: clarify comedi_buf_write_free()

Use the helper comedi_buf_write_n_allocated() to 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@visionengravers.com>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
index 95cbe36..fd2a92e 100644 (file)
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/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;