of: base: Change logic in of_alias_get_alias_list()

Check compatible string first before setting up bit in bitmap to also
cover cases that allocated bitfield is not big enough.
Show warning about it but let driver to continue to work with allocated
bitfield to keep at least some devices (included console which
is commonly close to serial0) to work.

Fixes: b1078c355d ("of: base: Introduce of_alias_get_alias_list() to check alias IDs")
Fixes: ae1cca3fa3 ("serial: uartps: Change uart ID port allocation")
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/of/base.c

@@ -1953,13 +1953,15 @@ EXPORT_SYMBOL_GPL(of_alias_get_id);
  * The function travels the lookup table to record alias ids for the given
  * device match structures and alias stem.
  *
- * Return:	0 or -ENOSYS when !CONFIG_OF
+ * Return:	0 or -ENOSYS when !CONFIG_OF or
+ *		-EOVERFLOW if alias ID is greater then allocated nbits
  */
 int of_alias_get_alias_list(const struct of_device_id *matches,
 			     const char *stem, unsigned long *bitmap,
 			     unsigned int nbits)
 {
 	struct alias_prop *app;
+	int ret = 0;
 
 	/* Zero bitmap field to make sure that all the time it is clean */
 	bitmap_zero(bitmap, nbits);
@@ -1976,21 +1978,21 @@ int of_alias_get_alias_list(const struct of_device_id *matches,
 			continue;
 		}
 
-		if (app->id >= nbits) {
-			pr_debug("%s: ID %d greater then bitmap field %d\n",
-				__func__, app->id, nbits);
-			continue;
-		}
-
 		if (of_match_node(matches, app->np)) {
 			pr_debug("%s: Allocated ID %d\n", __func__, app->id);
-			set_bit(app->id, bitmap);
+
+			if (app->id >= nbits) {
+				pr_warn("%s: ID %d >= than bitmap field %d\n",
+					__func__, app->id, nbits);
+				ret = -EOVERFLOW;
+			} else {
+				set_bit(app->id, bitmap);
+			}
 		}
-		/* Alias exists but is not compatible with matches */
 	}
 	mutex_unlock(&of_mutex);
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(of_alias_get_alias_list);
 

drivers/tty/serial/xilinx_uartps.c

@@ -1394,7 +1394,7 @@ static int cdns_get_id(struct platform_device *pdev)
 	if (!alias_bitmap_initialized) {
 		ret = of_alias_get_alias_list(cdns_uart_of_match, "serial",
 					      alias_bitmap, MAX_UART_INSTANCES);
-		if (ret) {
+		if (ret && ret != -EOVERFLOW) {
 			mutex_unlock(&bitmap_lock);
 			return ret;
 		}