From 02eac3ee4089d14f4896baea763126193fbe9b13 Mon Sep 17 00:00:00 2001
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: Thu, 17 Mar 2016 14:22:14 -0700
Subject: [PATCH] UPSTREAM: 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.

BUG=chromium:622499
TEST=Build image with match_string() enabled

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: David Airlie <airlied@linux.ie>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 56b060814e2d87d6646a85a2f4609c73587399ca)
Signed-off-by: Guenter Roeck <groeck@chromium.org>

Change-Id: I6075bb868e3578caa33561c85f4be57f4ea94cc2
Reviewed-on: https://chromium-review.googlesource.com/355210
Commit-Ready: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Jacob Chen <jacob2.chen@rock-chips.com>
---
 include/linux/string.h |  2 ++
 lib/string.c           | 26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index aa30789b0f65..5c08e42f95d5 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -133,6 +133,8 @@ static inline int strtobool(const char *s, bool *res)
 	return kstrtobool(s, 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 1a90db9bc6e1..ed83562a53ae 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -630,6 +630,32 @@ 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);
+
 #ifndef __HAVE_ARCH_MEMSET
 /**
  * memset - Fill a region of memory with the given value