part_efi: move uuid<->string conversion functions into lib/uuid.c

This commit introduces cleanup for uuid library.
Changes:
- move uuid<->string conversion functions into lib/uuid.c so they can be
  used by code outside part_efi.c.
- rename uuid_string() to uuid_bin_to_str() for consistency with existing
  uuid_str_to_bin()
- add an error return code to uuid_str_to_bin()
- update existing code to the new library functions.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Lukasz Majewski <l.majewski@samsung.com>
Cc: trini@ti.com

lib/uuid.c

@@ -5,18 +5,40 @@
  */
 
 #include <linux/ctype.h>
-#include "common.h"
+#include <errno.h>
+#include <common.h>
+
+#define UUID_STR_LEN		36
 
 /*
- * This is what a UUID string looks like.
+ * UUID - Universally Unique IDentifier - 128 bits unique number.
+ *        There are 5 versions and one variant of UUID defined by RFC4122
+ *        specification. Depends on version uuid number base on a time,
+ *        host name, MAC address or random data.
  *
- * x is a hexadecimal character. fields are separated by '-'s. When converting
- * to a binary UUID, le means the field should be converted to little endian,
- * and be means it should be converted to big endian.
+ * UUID binary format (16 bytes):
+ *
+ * 4B-2B-2B-2B-6B (big endian - network byte order)
+ *
+ * UUID string is 36 length of characters (36 bytes):
  *
  * 0        9    14   19   24
  * xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+ *    be     be   be   be       be
+ *
+ * where x is a hexadecimal character. Fields are separated by '-'s.
+ * When converting to a binary UUID, le means the field should be converted
+ * to little endian and be means it should be converted to big endian.
+ *
+ * UUID is also used as GUID (Globally Unique Identifier) with the same binary
+ * format but it differs in string format like below.
+ *
+ * GUID:
+ * 0        9    14   19   24
+ * xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
  *    le     le   le   be       be
+ *
+ * GUID is used e.g. in GPT (GUID Partition Table) as a partiions unique id.
  */
 
 int uuid_str_valid(const char *uuid)
@@ -43,14 +65,17 @@ int uuid_str_valid(const char *uuid)
 	return 1;
 }
 
-void uuid_str_to_bin(const char *uuid, unsigned char *out)
+int uuid_str_to_bin(char *uuid, unsigned char *out)
 {
 	uint16_t tmp16;
 	uint32_t tmp32;
 	uint64_t tmp64;
 
 	if (!uuid || !out)
-		return;
+		return -EINVAL;
+
+	if (strlen(uuid) != UUID_STR_LEN)
+		return -EINVAL;
 
 	tmp32 = cpu_to_le32(simple_strtoul(uuid, NULL, 16));
 	memcpy(out, &tmp32, 4);
@@ -66,4 +91,26 @@ void uuid_str_to_bin(const char *uuid, unsigned char *out)
 
 	tmp64 = cpu_to_be64(simple_strtoull(uuid + 24, NULL, 16));
 	memcpy(out + 10, (char *)&tmp64 + 2, 6);
+
+	return 0;
+}
+
+void uuid_bin_to_str(unsigned char *uuid, char *str)
+{
+	static const u8 le[16] = {3, 2, 1, 0, 5, 4, 7, 6, 8, 9, 10, 11,
+				  12, 13, 14, 15};
+	int i;
+
+	for (i = 0; i < 16; i++) {
+		sprintf(str, "%02x", uuid[le[i]]);
+		str += 2;
+		switch (i) {
+		case 3:
+		case 5:
+		case 7:
+		case 9:
+			*str++ = '-';
+			break;
+		}
+	}
 }