lib/string_helpers: Introduce string_upper() and string_lower() helpers

Provide the helpers for string conversions to upper and lower cases.
Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

include/linux/string_helpers.h

@@ -2,6 +2,7 @@
 #ifndef _LINUX_STRING_HELPERS_H_
 #define _LINUX_STRING_HELPERS_H_
 
+#include <linux/ctype.h>
 #include <linux/types.h>
 
 struct file;
@@ -75,6 +76,20 @@ static inline int string_escape_str_any_np(const char *src, char *dst,
 	return string_escape_str(src, dst, sz, ESCAPE_ANY_NP, only);
 }
 
+static inline void string_upper(char *dst, const char *src)
+{
+	do {
+		*dst++ = toupper(*src);
+	} while (*src++);
+}
+
+static inline void string_lower(char *dst, const char *src)
+{
+	do {
+		*dst++ = tolower(*src);
+	} while (*src++);
+}
+
 char *kstrdup_quotable(const char *src, gfp_t gfp);
 char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp);
 char *kstrdup_quotable_file(struct file *file, gfp_t gfp);