staging: comedi: rename comedi_buf_write_n_available

Rename the local function `comedi_buf_write_n_available()` to
`comedi_buf_write_n_unalloc()`.  It is the amount of unallocated space
available in the buffer that is available to be allocated for writing
and does not include the space that has already been allocated for
writing.  This is unlike the exported function
`comedi_buf_read_n_available()` which includes the space available to be
allocated for reading plus the space already allocated for reading.  The
new name breaks the unintentional naming symmetry (and also clears the
way for the old name to be reused for a new function).
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_buf.c

@@ -245,7 +245,7 @@ void comedi_buf_reset(struct comedi_subdevice *s)
 	async->events = 0;
 }
 
-static unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s)
+static unsigned int comedi_buf_write_n_unalloc(struct comedi_subdevice *s)
 {
 	struct comedi_async *async = s->async;
 	unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
@@ -268,10 +268,10 @@ unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s,
 				    unsigned int nbytes)
 {
 	struct comedi_async *async = s->async;
-	unsigned int available = comedi_buf_write_n_available(s);
+	unsigned int unalloc = comedi_buf_write_n_unalloc(s);
 
-	if (nbytes > available)
-		nbytes = available;
+	if (nbytes > unalloc)
+		nbytes = unalloc;
 
 	async->buf_write_alloc_count += nbytes;
 
@@ -557,8 +557,7 @@ unsigned int comedi_buf_write_samples(struct comedi_subdevice *s,
 	 * If not, clamp the nsamples to the number that will fit, flag the
 	 * buffer overrun and add the samples that fit.
 	 */
-	max_samples = comedi_bytes_to_samples(s,
-					      comedi_buf_write_n_available(s));
+	max_samples = comedi_bytes_to_samples(s, comedi_buf_write_n_unalloc(s));
 	if (nsamples > max_samples) {
 		dev_warn(s->device->class_dev, "buffer overrun\n");
 		s->async->events |= COMEDI_CB_OVERFLOW;