kconfig: environment symbol support

Add the possibility to import a value from the environment into kconfig
via the option syntax. Beside flexibility this has the advantage
providing proper dependencies.
Documented the options syntax.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index a7dfc82fc858..99e3d02d1cfc 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -34,6 +34,8 @@ struct symbol *sym_defconfig_list;
 struct symbol *modules_sym;
 tristate modules_val;
 
+struct expr *sym_env_list;
+
 void sym_add_default(struct symbol *sym, const char *def)
 {
         struct property *prop = prop_alloc(P_DEFAULT, sym);
@@ -117,6 +119,15 @@ struct property *sym_get_choice_prop(struct symbol *sym)
         return NULL;
 }
 
+struct property *sym_get_env_prop(struct symbol *sym)
+{
+        struct property *prop;
+
+        for_all_properties(sym, prop, P_ENV)
+                return prop;
+        return NULL;
+}
+
 struct property *sym_get_default_prop(struct symbol *sym)
 {
         struct property *prop;
@@ -346,6 +357,9 @@ void sym_calc_value(struct symbol *sym)
                 ;
         }
 
+        if (sym->flags & SYMBOL_AUTO)
+                sym->flags &= ~SYMBOL_WRITE;
+
         sym->curr = newval;
         if (sym_is_choice(sym) && newval.tri == yes)
                 sym->curr.val = sym_calc_choice(sym);
@@ -860,6 +874,8 @@ const char *prop_get_type_name(enum prop_type type)
         switch (type) {
         case P_PROMPT:
                 return "prompt";
+        case P_ENV:
+                return "env";
         case P_COMMENT:
                 return "comment";
         case P_MENU:
@@ -877,3 +893,32 @@ const char *prop_get_type_name(enum prop_type type)
         }
         return "unknown";
 }
+
+void prop_add_env(const char *env)
+{
+        struct symbol *sym, *sym2;
+        struct property *prop;
+        char *p;
+
+        sym = current_entry->sym;
+        sym->flags |= SYMBOL_AUTO;
+        for_all_properties(sym, prop, P_ENV) {
+                sym2 = prop_get_symbol(prop);
+                if (strcmp(sym2->name, env))
+                        menu_warn(current_entry, "redefining environment symbol from %s",
+                                  sym2->name);
+                return;
+        }
+
+        prop = prop_alloc(P_ENV, sym);
+        prop->expr = expr_alloc_symbol(sym_lookup(env, 1));
+
+        sym_env_list = expr_alloc_one(E_LIST, sym_env_list);
+        sym_env_list->right.sym = sym;
+
+        p = getenv(env);
+        if (p)
+                sym_add_default(sym, p);
+        else
+                menu_warn(current_entry, "environment variable %s undefined", env);
+}