[PATCH v2 1/4] kconfig: save values imported from environment into config file

[Konstantin Khlebnikov <koct9i@gmail.com>]

After this patch option env="..." behaves more like user input.
Environment variable becomes optional, its last state is saved in config.

Impact of this change is minimal. This option is used only three times:
for ARCH, SRCARCH and KERNELVERSION. All of them are always defined by
root Makefile.

Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
---
 Documentation/kbuild/kconfig-language.txt |   10 ++++------
 scripts/kconfig/confdata.c                |   26 ++++++++++++++++++++++++++
 scripts/kconfig/expr.h                    |    2 +-
 scripts/kconfig/symbol.c                  |    3 ---
 4 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
index 350f733..0dad00a 100644
--- a/Documentation/kbuild/kconfig-language.txt
+++ b/Documentation/kbuild/kconfig-language.txt
@@ -149,13 +149,11 @@ applicable everywhere (see syntax).
     enables the third modular state for all config symbols.
     At most one symbol may have the "modules" option set.
 
-  - "env"=<value>
+  - "env"=<varname>
     This imports the environment variable into Kconfig. It behaves like
-    a default, except that the value comes from the environment, this
-    also means that the behaviour when mixing it with normal defaults is
-    undefined at this point. The symbol is currently not exported back
-    to the build environment (if this is desired, it can be done via
-    another symbol).
+    the user input, except that the value comes from the environment.
+    Environment variable overrides all defaults and value from the file.
+    If environment variable is not defined this option has no effect.
 
   - "allnoconfig_y"
     This declares the symbol as one that should have the value y when
diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index f88d90f..5cb0034 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -404,6 +404,30 @@ setsym:
 	return 0;
 }
 
+static void conf_read_env(void)
+{
+	struct symbol *sym, *env_sym;
+	struct property *prop;
+	struct expr *expr;
+	char *value;
+
+	expr_list_for_each_sym(sym_env_list, expr, sym) {
+		prop = sym_get_env_prop(sym);
+		env_sym = prop_get_symbol(prop);
+		value = getenv(env_sym->name);
+		if (value) {
+			sym_calc_value(sym);
+			if (!sym_set_string_value(sym, value))
+				conf_warning("evironment variable %s value "
+					      "'%s' invalid for %s",
+					      env_sym->name, value, sym->name);
+		} else if (!(sym->flags & SYMBOL_DEF_USER))
+			conf_warning("neither symbol %s nor evironment "
+					"variable %s are defined",
+				       sym->name, env_sym->name);
+	}
+}
+
 int conf_read(const char *name)
 {
 	struct symbol *sym;
@@ -414,6 +438,8 @@ int conf_read(const char *name)
 	if (conf_read_simple(name, S_DEF_USER))
 		return 1;
 
+	conf_read_env();
+
 	for_all_symbols(i, sym) {
 		sym_calc_value(sym);
 		if (sym_is_choice(sym) || (sym->flags & SYMBOL_AUTO))
diff --git a/scripts/kconfig/expr.h b/scripts/kconfig/expr.h
index 412ea8a..8d9bbc9 100644
--- a/scripts/kconfig/expr.h
+++ b/scripts/kconfig/expr.h
@@ -95,7 +95,7 @@ struct symbol {
 #define SYMBOL_OPTIONAL   0x0100  /* choice is optional - values can be 'n' */
 #define SYMBOL_WRITE      0x0200  /* write symbol to file (KCONFIG_CONFIG) */
 #define SYMBOL_CHANGED    0x0400  /* ? */
-#define SYMBOL_AUTO       0x1000  /* value from environment variable */
+#define SYMBOL_AUTO       0x1000  /* calculated value - not saved into file */
 #define SYMBOL_CHECKED    0x2000  /* used during dependency checking */
 #define SYMBOL_WARNED     0x8000  /* warning has been issued */
 
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 7caabdb..9dce811 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -1350,7 +1350,6 @@ static void prop_add_env(const char *env)
 	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))
@@ -1368,6 +1367,4 @@ static void prop_add_env(const char *env)
 	p = getenv(env);
 	if (p)
 		sym_add_default(sym, p);
-	else
-		menu_warn(current_entry, "environment variable %s undefined", env);
 }