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kconfig: Clarify expression rewriting 

menu_finalize() is one of the more opaque parts of Kconfig, and I need
to make some changes to it to fix an issue related to modules. Add some
comments related to expression rewriting and dependency propagation as a
review aid. They will also help other people trying to understand the
code.

Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
This commit is contained in:
Ulf Magnusson 2017-10-05 14:01:14 +02:00 committed by Masahiro Yamada
parent 9a826842ff
commit fa8cedaef8
1 changed files with 52 additions and 0 deletions
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52
scripts/kconfig/menu.c
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@ -306,6 +306,11 @@ void menu_finalize(struct menu *parent)
sym = parent->sym;
if (parent->list) {
/*
* This menu node has children. We (recursively) process them
* and propagate parent dependencies before moving on.
*/
if (sym && sym_is_choice(sym)) {
if (sym->type == S_UNKNOWN) {
/* find the first choice value to find out choice type */
@ -329,24 +334,66 @@ void menu_finalize(struct menu *parent)
else
parentdep = parent->dep;
/* For each child menu node... */
for (menu = parent->list; menu; menu = menu->next) {
/*
* Propagate parent dependencies to the child menu
* node, also rewriting and simplifying expressions
*/
basedep = expr_transform(menu->dep);
basedep = expr_alloc_and(expr_copy(parentdep), basedep);
basedep = expr_eliminate_dups(basedep);
menu->dep = basedep;
if (menu->sym)
/*
* Note: For symbols, all prompts are included
* too in the symbol's own property list
*/
prop = menu->sym->prop;
else
/*
* For non-symbol menu nodes, we just need to
* handle the prompt
*/
prop = menu->prompt;
/* For each property... */
for (; prop; prop = prop->next) {
if (prop->menu != menu)
/*
* Two possibilities:
*
* 1. The property lacks dependencies
* and so isn't location-specific,
* e.g. an 'option'
*
* 2. The property belongs to a symbol
* defined in multiple locations and
* is from some other location. It
* will be handled there in that
* case.
*
* Skip the property.
*/
continue;
/*
* Propagate parent dependencies to the
* property's condition, rewriting and
* simplifying expressions at the same time
*/
dep = expr_transform(prop->visible.expr);
dep = expr_alloc_and(expr_copy(basedep), dep);
dep = expr_eliminate_dups(dep);
if (menu->sym && menu->sym->type != S_TRISTATE)
dep = expr_trans_bool(dep);
prop->visible.expr = dep;
/*
* Handle selects and implies, which modify the
* dependencies of the selected/implied symbol
*/
if (prop->type == P_SELECT) {
struct symbol *es = prop_get_symbol(prop);
es->rev_dep.expr = expr_alloc_or(es->rev_dep.expr,
@ -358,6 +405,11 @@ void menu_finalize(struct menu *parent)
}
}
}
/*
* Recursively process children in the same fashion before
* moving on
*/
for (menu = parent->list; menu; menu = menu->next)
menu_finalize(menu);
} else if (sym) {