kconfig: split out code touching a file to conf_touch_dep()

conf_touch_deps() iterates over symbols, touching corresponding
include/config/*.h files as needed.

Split the part that touches a single file into a new helper so it can
be reused.

The new helper, conf_touch_dep(), takes a symbol name as a parameter,
and touches the corresponding include/config/*.h file.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/confdata.c

@@ -74,6 +74,47 @@ static int make_parent_dir(const char *path)
 	return 0;
 }
 
+static char depfile_path[PATH_MAX];
+static size_t depfile_prefix_len;
+
+/* touch depfile for symbol 'name' */
+static int conf_touch_dep(const char *name)
+{
+	int fd, ret;
+	const char *s;
+	char *d, c;
+
+	/* check overflow: prefix + name + ".h" + '\0' must fit in buffer. */
+	if (depfile_prefix_len + strlen(name) + 3 > sizeof(depfile_path))
+		return -1;
+
+	d = depfile_path + depfile_prefix_len;
+	s = name;
+
+	while ((c = *s++))
+		*d++ = (c == '_') ? '/' : tolower(c);
+	strcpy(d, ".h");
+
+	/* Assume directory path already exists. */
+	fd = open(depfile_path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+	if (fd == -1) {
+		if (errno != ENOENT)
+			return -1;
+
+		ret = make_parent_dir(depfile_path);
+		if (ret)
+			return ret;
+
+		/* Try it again. */
+		fd = open(depfile_path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
+		if (fd == -1)
+			return -1;
+	}
+	close(fd);
+
+	return 0;
+}
+
 struct conf_printer {
 	void (*print_symbol)(FILE *, struct symbol *, const char *, void *);
 	void (*print_comment)(FILE *, const char *, void *);
@@ -909,21 +950,16 @@ static int conf_write_dep(const char *name)
 static int conf_touch_deps(void)
 {
 	const char *name;
-	char path[PATH_MAX+1];
-	char *s, *d, c;
 	struct symbol *sym;
-	int res, i, fd;
+	int res, i;
+
+	strcpy(depfile_path, "include/config/");
+	depfile_prefix_len = strlen(depfile_path);
 
 	name = conf_get_autoconfig_name();
 	conf_read_simple(name, S_DEF_AUTO);
 	sym_calc_value(modules_sym);
 
-	if (make_parent_dir("include/config/foo.h"))
-		return 1;
-	if (chdir("include/config"))
-		return 1;
-
-	res = 0;
 	for_all_symbols(i, sym) {
 		sym_calc_value(sym);
 		if ((sym->flags & SYMBOL_NO_WRITE) || !sym->name)
@@ -975,42 +1011,12 @@ static int conf_touch_deps(void)
 		 *	different from 'no').
 		 */
 
-		/* Replace all '_' and append ".h" */
-		s = sym->name;
-		d = path;
-		while ((c = *s++)) {
-			c = tolower(c);
-			*d++ = (c == '_') ? '/' : c;
-		}
-		strcpy(d, ".h");
-
-		/* Assume directory path already exists. */
-		fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
-		if (fd == -1) {
-			if (errno != ENOENT) {
-				res = 1;
-				break;
-			}
-
-			if (make_parent_dir(path)) {
-				res = 1;
-				goto out;
-			}
-
-			/* Try it again. */
-			fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
-			if (fd == -1) {
-				res = 1;
-				break;
-			}
-		}
-		close(fd);
+		res = conf_touch_dep(sym->name);
+		if (res)
+			return res;
 	}
-out:
-	if (chdir("../.."))
-		return 1;
 
-	return res;
+	return 0;
 }
 
 int conf_write_autoconf(int overwrite)