staging: comedi: ni_routes: Refactor ni_find_valid_routes()

Split out the loops in `ni_find_valid_routes()` into separate functions:

* ni_find_route_values(device_family) to find the list of route values
  for a device family (e.g "ni-mseries"); and
* ni_find_valid_routes(board_name) to find the set of valid routes for a
  board name.

The functions above return `NULL` if the information is not found (as we
do not currently have the routing information available for all
supported boards).

Cc: Éric Piel <piel@delmic.com>
Cc: Spencer E. Olson <olsonse@umich.edu>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20200207151400.272678-2-abbotti@mev.co.ukSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/ni_routes.c

@@ -50,20 +50,13 @@
 #define RVi(table, src, dest)	((table)[(dest) * NI_NUM_NAMES + (src)])
 
 /*
- * Find the proper route_values and ni_device_routes tables for this particular
- * device.
- *
- * Return: -ENODATA if either was not found; 0 if both were found.
+ * Find the route values for a device family.
  */
-static int ni_find_device_routes(const char *device_family,
-				 const char *board_name,
-				 struct ni_route_tables *tables)
+static const u8 *ni_find_route_values(const char *device_family)
 {
-	const struct ni_device_routes *dr = NULL;
 	const u8 *rv = NULL;
 	int i;
 
-	/* First, find the register_values table for this device family */
 	for (i = 0; ni_all_route_values[i]; ++i) {
 		if (memcmp(ni_all_route_values[i]->family, device_family,
 			   strnlen(device_family, 30)) == 0) {
@@ -71,8 +64,18 @@ static int ni_find_device_routes(const char *device_family,
 			break;
 		}
 	}
+	return rv;
+}
+
+/*
+ * Find the valid routes for a board.
+ */
+static const struct ni_device_routes *
+ni_find_valid_routes(const char *board_name)
+{
+	const struct ni_device_routes *dr = NULL;
+	int i;
 
-	/* Second, find the set of routes valid for this device. */
 	for (i = 0; ni_device_routes_list[i]; ++i) {
 		if (memcmp(ni_device_routes_list[i]->device, board_name,
 			   strnlen(board_name, 30)) == 0) {
@@ -80,6 +83,27 @@ static int ni_find_device_routes(const char *device_family,
 			break;
 		}
 	}
+	return dr;
+}
+
+/*
+ * Find the proper route_values and ni_device_routes tables for this particular
+ * device.
+ *
+ * Return: -ENODATA if either was not found; 0 if both were found.
+ */
+static int ni_find_device_routes(const char *device_family,
+				 const char *board_name,
+				 struct ni_route_tables *tables)
+{
+	const struct ni_device_routes *dr;
+	const u8 *rv;
+
+	/* First, find the register_values table for this device family */
+	rv = ni_find_route_values(device_family);
+
+	/* Second, find the set of routes valid for this device. */
+	dr = ni_find_valid_routes(board_name);
 
 	tables->route_values = rv;
 	tables->valid_routes = dr;