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;