lib/string: introduce match_string() helper

Occasionally we have to search for an occurrence of a string in an array
of strings.  Make a simple helper for that purpose.

Signed-off-by: Andy Shevchenko <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Bartlomiej Zolnierkiewicz <[email protected]>
Cc: David Airlie <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: Dmitry Eremin-Solenikov <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Heikki Krogerus <[email protected]>
Cc: Linus Walleij <[email protected]>
Cc: Mika Westerberg <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Cc: Sebastian Reichel <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

2 files changed, 28 insertions, 0 deletions

diff --git a/include/linux/string.h b/include/linux/string.h
index 9eebc66d957a..0f235e80d355 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -130,6 +130,8 @@ extern void argv_free(char **argv);
 extern bool sysfs_streq(const char *s1, const char *s2);
 extern int strtobool(const char *s, bool *res);
 
+int match_string(const char * const *array, size_t n, const char *string);
+
 #ifdef CONFIG_BINARY_PRINTF
 int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args);
 int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf);
diff --git a/lib/string.c b/lib/string.c
index 0323c0d5629a..e9c9db161d2c 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -631,6 +631,32 @@ bool sysfs_streq(const char *s1, const char *s2)
 EXPORT_SYMBOL(sysfs_streq);
 
 /**
+ * match_string - matches given string in an array
+ * @array:	array of strings
+ * @n:		number of strings in the array or -1 for NULL terminated arrays
+ * @string:	string to match with
+ *
+ * Return:
+ * index of a @string in the @array if matches, or %-EINVAL otherwise.
+ */
+int match_string(const char * const *array, size_t n, const char *string)
+{
+	int index;
+	const char *item;
+
+	for (index = 0; index < n; index++) {
+		item = array[index];
+		if (!item)
+			break;
+		if (!strcmp(item, string))
+			return index;
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL(match_string);
+
+/**
  * strtobool - convert common user inputs into boolean values
  * @s: input string
  * @res: result