kconfig: Document 'if' flattening logic

[carl9170fw.git] / config / menu.c

diff --git a/config/menu.c b/config/menu.c
index 47bec3434fef16f1b0c46e0f8d908ee704aa57ca..af66065733bb636be638d72c9fe4492692462d28 100644 (file)
--- a/config/menu.c
+++ b/config/menu.c
@@ -323,6 +323,13 @@ void menu_finalize(struct menu *parent)
                                if (menu->sym && menu->sym->type == S_UNKNOWN)
                                        menu_set_type(sym->type);
                        }
+
+                       /*
+                        * Use the choice itself as the parent dependency of
+                        * the contained items. This turns the mode of the
+                        * choice into an upper bound on the visibility of the
+                        * choice value symbols.
+                        */
                        parentdep = expr_alloc_symbol(sym);
                } else if (parent->prompt)
                        parentdep = parent->prompt->visible.expr;
@@ -525,6 +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;
@@ -549,6 +585,15 @@ void menu_finalize(struct menu *parent)
                sym->flags |= SYMBOL_WARNED;
        }
 
+       /*
+        * For non-optional choices, add a reverse dependency (corresponding to
+        * a select) of '<visibility> && m'. This prevents the user from
+        * setting the choice mode to 'n' when the choice is visible.
+        *
+        * This would also work for non-choice symbols, but only non-optional
+        * choices clear SYMBOL_OPTIONAL as of writing. Choices are implemented
+        * as a type of symbol.
+        */
        if (sym && !sym_is_optional(sym) && parent->prompt) {
                sym->rev_dep.expr = expr_alloc_or(sym->rev_dep.expr,
                                expr_alloc_and(parent->prompt->visible.expr,