regmap: debugfs: document why we don't create the debugfs entries

This is a follow-up to commit a5ba91c ("regmap: debugfs: emit a
debug message when locking is disabled"). I figured that a user may
see this message, grep the code, come to this place and he still won't
know why we actually disabled debugfs.

Add a comment explaining the reason.

Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regmap-debugfs.c

@@ -529,6 +529,13 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
 	struct regmap_range_node *range_node;
 	const char *devname = "dummy";
 
+	/*
+	 * Userspace can initiate reads from the hardware over debugfs.
+	 * Normally internal regmap structures and buffers are protected with
+	 * a mutex or a spinlock, but if the regmap owner decided to disable
+	 * all locking mechanisms, this is no longer the case. For safety:
+	 * don't create the debugfs entries if locking is disabled.
+	 */
 	if (map->debugfs_disable) {
 		dev_dbg(map->dev, "regmap locking disabled - not creating debugfs entries\n");
 		return;