kconfig: Document 'if' flattening logic

It is not obvious that this might refer to an 'if', making the code
pretty cryptic:

	if (menu->list && (!menu->prompt || !menu->prompt->text)) {

Kconfig keeps the 'if' menu nodes even after flattening. Reflect that in
the example to be accurate.

No functional changes. Only comments added.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
index dcf22008b2d6..af66065733bb 100644
--- a/scripts/kconfig/menu.c
+++ b/scripts/kconfig/menu.c
@@ -532,6 +532,35 @@ void menu_finalize(struct menu *parent)
                         *ep = expr_alloc_one(E_LIST, NULL);
                         (*ep)->right.sym = menu->sym;
                 }
+
+                /*
+                 * This code serves two purposes:
+                 *
+                 * (1) Flattening 'if' blocks, which do not specify a submenu
+                 *     and only add dependencies.
+                 *
+                 *     (Automatic submenu creation might still create a submenu
+                 *     from an 'if' before this code runs.)
+                 *
+                 * (2) "Undoing" any automatic submenus created earlier below
+                 *     promptless symbols.
+                 *
+                 * Before:
+                 *
+                 *      A
+                 *      if ... (or promptless symbol)
+                 *       +-B
+                 *       +-C
+                 *      D
+                 *
+                 * After:
+                 *
+                 *      A
+                 *      if ... (or promptless symbol)
+                 *      B
+                 *      C
+                 *      D
+                 */
                 if (menu->list && (!menu->prompt || !menu->prompt->text)) {
                         for (last_menu = menu->list; ; last_menu = last_menu->next) {
                                 last_menu->parent = parent;