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* Copyright 2011 Calxeda, Inc.
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* SPDX-License-Identifier: GPL-2.0+
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#include <linux/ctype.h>
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* UUID - Universally Unique IDentifier - 128 bits unique number.
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* There are 5 versions and one variant of UUID defined by RFC4122
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* specification. A UUID contains a set of fields. The set varies
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* depending on the version of the UUID, as shown below:
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* - time, MAC address(v1),
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* - MD5 of name or URL(v3),
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* - SHA-1 of name or URL(v5),
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* timestamp - 60-bit: time_low, time_mid, time_hi_and_version
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* version - 4 bit (bit 4 through 7 of the time_hi_and_version)
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* clock seq - 14 bit: clock_seq_hi_and_reserved, clock_seq_low
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* variant: - bit 6 and 7 of clock_seq_hi_and_reserved
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* source: https://www.ietf.org/rfc/rfc4122.txt
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* UUID binary format (16 bytes):
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* 4B-2B-2B-2B-6B (big endian - network byte order)
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* UUID string is 36 length of characters (36 bytes):
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* xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
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* where x is a hexadecimal character. Fields are separated by '-'s.
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* When converting to a binary UUID, le means the field should be converted
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* to little endian and be means it should be converted to big endian.
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* UUID is also used as GUID (Globally Unique Identifier) with the same binary
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* format but it differs in string format like below.
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* xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
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* GUID is used e.g. in GPT (GUID Partition Table) as a partiions unique id.
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int uuid_str_valid(const char *uuid)
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for (i = 0, valid = 1; uuid[i] && valid; i++) {
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case 8: case 13: case 18: case 23:
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valid = (uuid[i] == '-');
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valid = isxdigit(uuid[i]);
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if (i != UUID_STR_LEN || !valid)
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* uuid_str_to_bin() - convert string UUID or GUID to big endian binary data.
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* @param uuid_str - pointer to UUID or GUID string [37B]
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* @param uuid_bin - pointer to allocated array for big endian output [16B]
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* @str_format - UUID string format: 0 - UUID; 1 - GUID
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int uuid_str_to_bin(char *uuid_str, unsigned char *uuid_bin, int str_format)
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if (!uuid_str_valid(uuid_str))
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if (str_format == UUID_STR_FORMAT_STD) {
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tmp32 = cpu_to_be32(simple_strtoul(uuid_str, NULL, 16));
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memcpy(uuid_bin, &tmp32, 4);
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tmp16 = cpu_to_be16(simple_strtoul(uuid_str + 9, NULL, 16));
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memcpy(uuid_bin + 4, &tmp16, 2);
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tmp16 = cpu_to_be16(simple_strtoul(uuid_str + 14, NULL, 16));
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memcpy(uuid_bin + 6, &tmp16, 2);
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tmp32 = cpu_to_le32(simple_strtoul(uuid_str, NULL, 16));
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memcpy(uuid_bin, &tmp32, 4);
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tmp16 = cpu_to_le16(simple_strtoul(uuid_str + 9, NULL, 16));
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memcpy(uuid_bin + 4, &tmp16, 2);
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tmp16 = cpu_to_le16(simple_strtoul(uuid_str + 14, NULL, 16));
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memcpy(uuid_bin + 6, &tmp16, 2);
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tmp16 = cpu_to_be16(simple_strtoul(uuid_str + 19, NULL, 16));
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memcpy(uuid_bin + 8, &tmp16, 2);
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tmp64 = cpu_to_be64(simple_strtoull(uuid_str + 24, NULL, 16));
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memcpy(uuid_bin + 10, (char *)&tmp64 + 2, 6);
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* uuid_bin_to_str() - convert big endian binary data to string UUID or GUID.
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* @param uuid_bin - pointer to binary data of UUID (big endian) [16B]
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* @param uuid_str - pointer to allocated array for output string [37B]
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* @str_format - UUID string format: 0 - UUID; 1 - GUID
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void uuid_bin_to_str(unsigned char *uuid_bin, char *uuid_str, int str_format)
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const u8 uuid_char_order[UUID_BIN_LEN] = {0, 1, 2, 3, 4, 5, 6, 7, 8,
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9, 10, 11, 12, 13, 14, 15};
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const u8 guid_char_order[UUID_BIN_LEN] = {3, 2, 1, 0, 5, 4, 7, 6, 8,
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9, 10, 11, 12, 13, 14, 15};
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const u8 *char_order;
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* UUID and GUID bin data - always in big endian:
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if (str_format == UUID_STR_FORMAT_STD)
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char_order = uuid_char_order;
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char_order = guid_char_order;
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for (i = 0; i < 16; i++) {
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sprintf(uuid_str, "%02x", uuid_bin[char_order[i]]);
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* gen_rand_uuid() - this function generates a random binary UUID version 4.
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* In this version all fields beside 4 bits of version and
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* 2 bits of variant are randomly generated.
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* @param uuid_bin - pointer to allocated array [16B]. Output is in big endian.
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#if defined(CONFIG_RANDOM_UUID) || defined(CONFIG_CMD_UUID)
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void gen_rand_uuid(unsigned char *uuid_bin)
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unsigned int *ptr = (unsigned int *)&uuid;
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/* Set all fields randomly */
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for (i = 0; i < sizeof(struct uuid) / sizeof(*ptr); i++)
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*(ptr + i) = cpu_to_be32(rand());
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clrsetbits_be16(&uuid.time_hi_and_version,
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UUID_VERSION << UUID_VERSION_SHIFT);
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clrsetbits_8(&uuid.clock_seq_hi_and_reserved,
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UUID_VARIANT << UUID_VARIANT_SHIFT);
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memcpy(uuid_bin, &uuid, sizeof(struct uuid));
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* gen_rand_uuid_str() - this function generates UUID v4 (random) in two string
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* formats UUID or GUID.
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* @param uuid_str - pointer to allocated array [37B].
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* @param - uuid output type: UUID - 0, GUID - 1
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void gen_rand_uuid_str(char *uuid_str, int str_format)
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unsigned char uuid_bin[UUID_BIN_LEN];
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/* Generate UUID (big endian) */
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gen_rand_uuid(uuid_bin);
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/* Convert UUID bin to UUID or GUID formated STRING */
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uuid_bin_to_str(uuid_bin, uuid_str, str_format);
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#ifdef CONFIG_CMD_UUID
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int do_uuid(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
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char uuid[UUID_STR_LEN + 1];
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if (!strcmp(argv[0], "uuid"))
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str_format = UUID_STR_FORMAT_STD;
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str_format = UUID_STR_FORMAT_GUID;
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return CMD_RET_USAGE;
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gen_rand_uuid_str(uuid, str_format);
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printf("%s\n", uuid);
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setenv(argv[1], uuid);
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return CMD_RET_SUCCESS;
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U_BOOT_CMD(uuid, CONFIG_SYS_MAXARGS, 1, do_uuid,
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"UUID - generate random Universally Unique Identifier",
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"varname: for set result in a environment variable\n"
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U_BOOT_CMD(guid, CONFIG_SYS_MAXARGS, 1, do_uuid,
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"GUID - generate Globally Unique Identifier based on random UUID",
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"varname: for set result in a environment variable\n"
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#endif /* CONFIG_CMD_UUID */
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#endif /* CONFIG_RANDOM_UUID || CONFIG_CMD_UUID */