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, 21 insertions, 2 deletions

diff --git a/scripts/kconfig/util.c b/scripts/kconfig/util.c
index e1cad924c0a4..f8e73c039dc8 100644
--- a/scripts/kconfig/util.c
+++ b/scripts/kconfig/util.c
@@ -29,6 +29,8 @@ struct file *file_lookup(const char *name)
 /* write a dependency file as used by kbuild to track dependencies */
 int file_write_dep(const char *name)
 {
+        struct symbol *sym, *env_sym;
+        struct expr *e;
         struct file *file;
         FILE *out;
 
@@ -45,8 +47,25 @@ int file_write_dep(const char *name)
                         fprintf(out, "\t%s\n", file->name);
         }
         fprintf(out, "\ninclude/config/auto.conf: \\\n"
-                     "\t$(deps_config)\n\n"
-                     "$(deps_config): ;\n");
+                     "\t$(deps_config)\n\n");
+
+        expr_list_for_each_sym(sym_env_list, e, sym) {
+                struct property *prop;
+                const char *value;
+
+                prop = sym_get_env_prop(sym);
+                env_sym = prop_get_symbol(prop);
+                if (!env_sym)
+                        continue;
+                value = getenv(env_sym->name);
+                if (!value)
+                        value = "";
+                fprintf(out, "ifneq \"$(%s)\" \"%s\"\n", env_sym->name, value);
+                fprintf(out, "include/config/auto.conf: FORCE\n");
+                fprintf(out, "endif\n");
+        }
+
+        fprintf(out, "\n$(deps_config): ;\n");
         fclose(out);
         rename("..config.tmp", name);
         return 0;