kconfig: add helper to set config symbol from environment variable

Add conf_set_env_sym() that can set an already defined symbol
based on the value of an environment variable.

Unknown symbols are silently ignored.
A warning is printed if the value of the environment variable
is unexpected.

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

2 files changed, 28 insertions, 0 deletions

diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index e0f402f3b75d..e4fa3f302541 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -145,6 +145,33 @@ static int conf_set_sym_val(struct symbol *sym, int def, int def_flags, char *p)
         return 0;
 }
 
+/* Read an environment variable and assign the value to the symbol */
+int conf_set_env_sym(const char *env, const char *symname, int def)
+{
+        struct symbol *sym;
+        char *p;
+        int def_flags;
+
+        p = getenv(env);
+        if (p) {
+                char warning[200];
+                sprintf(warning, "Environment variable (%s = \"%s\")", env, p);
+                conf_filename = warning;
+                def_flags = SYMBOL_DEF << def;
+                if (def == S_DEF_USER) {
+                        sym = sym_find(symname);
+                        if (!sym)
+                                return 1;
+                } else {
+                        sym = sym_lookup(symname, 0);
+                        if (sym->type == S_UNKNOWN)
+                                sym->type = S_OTHER;
+                }
+                conf_set_sym_val(sym, def, def_flags, p);
+        }
+        return 0;
+}
+
 int conf_read_simple(const char *name, int def)
 {
         FILE *in = NULL;
diff --git a/scripts/kconfig/lkc_proto.h b/scripts/kconfig/lkc_proto.h
index 4d09f6ddefe3..dca294e90cc3 100644
--- a/scripts/kconfig/lkc_proto.h
+++ b/scripts/kconfig/lkc_proto.h
@@ -1,6 +1,7 @@
 
 /* confdata.c */
 P(conf_parse,void,(const char *name));
+P(conf_set_env_sym,int,(const char *envname, const char *symname, int def));
 P(conf_read,int,(const char *name));
 P(conf_read_simple,int,(const char *name, int));
 P(conf_write,int,(const char *name));