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kconfig: Document automatic submenu creation code 

It's tricky to figure out what it does (and how) without staring at the
code for a long time. Document it to make it more transparent.

No functional changes. Only comments added.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit is contained in:
Ulf Magnusson 2017-10-08 19:42:18 +02:00 committed by Masahiro Yamada
parent 7cf33f88e2
commit 05cccce580
1 changed files with 38 additions and 0 deletions
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38
scripts/kconfig/menu.c
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@ -418,25 +418,63 @@ void menu_finalize(struct menu *parent)
for (menu = parent->list; menu; menu = menu->next)
menu_finalize(menu);
} else if (sym) {
/*
* Automatic submenu creation. If sym is a symbol and A, B, C,
* ... are consecutive items (symbols, menus, ifs, etc.) that
* all depend on sym, then the following menu structure is
* created:
*
* sym
* +-A
* +-B
* +-C
* ...
*
* This also works recursively, giving the following structure
* if A is a symbol and B depends on A:
*
* sym
* +-A
* | +-B
* +-C
* ...
*/
basedep = parent->prompt ? parent->prompt->visible.expr : NULL;
basedep = expr_trans_compare(basedep, E_UNEQUAL, &symbol_no);
basedep = expr_eliminate_dups(expr_transform(basedep));
/* Examine consecutive elements after sym */
last_menu = NULL;
for (menu = parent->next; menu; menu = menu->next) {
dep = menu->prompt ? menu->prompt->visible.expr : menu->dep;
if (!expr_contains_symbol(dep, sym))
/* No dependency, quit */
break;
if (expr_depends_symbol(dep, sym))
/* Absolute dependency, put in submenu */
goto next;
/*
* Also consider it a dependency on sym if our
* dependencies contain sym and are a "superset" of
* sym's dependencies, e.g. '(sym || Q) && R' when sym
* depends on R.
*
* Note that 'R' might be from an enclosing menu or if,
* making this a more common case than it might seem.
*/
dep = expr_trans_compare(dep, E_UNEQUAL, &symbol_no);
dep = expr_eliminate_dups(expr_transform(dep));
dep2 = expr_copy(basedep);
expr_eliminate_eq(&dep, &dep2);
expr_free(dep);
if (!expr_is_yes(dep2)) {
/* Not superset, quit */
expr_free(dep2);
break;
}
/* Superset, put in submenu */
expr_free(dep2);
next:
menu_finalize(menu);