u-boot/doc/README.gpt

1 # SPDX-License-Identifier: GPL-2.0+
9 - UUID -(Universally Unique Identifier)
10 - GUID - (Globally Unique ID)
11 - EFI - (Extensible Firmware Interface)
12 - UEFI - (Unified EFI) - EFI evolution
13 - GPT (GUID Partition Table) - it is the EFI standard part
14 - partitions - lists of available partitions (defined at u-boot):
20 the gpt command in u-boot.
25 GPT for marking disks/partitions is using the UUID. It is supposed to be a
26 globally unique value. A UUID is a 16-byte (128-bit) number. The number of
29 separated by hyphens, in the form 8-4-4-4-12 for a total of 36 characters
32 For instance, GUID of Basic data partition: EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
33 and GUID of Linux filesystem data: 0FC63DAF-8483-4772-8E79-3D69D8477DE4
38 Successive versions are using MD5 hash, random numbers and SHA-1 hash. All major
46 	-------
48 	--------------------------------------------------
50 	----------------------------------------------------------
52 	-------------------------------------------------- GPT
54 	--------------------------------------------------
55 	LBA 3          |Entries 5 - 128                  |
58 	----------------------------------------------------------
61 		       -----------------------------------
64 		       -----------------------------------
67 	----------------------------------------------------------
68 	LBA -34        |Entry 1|Entry 2| Entry 3| Entry 4| Backup
69 	-------------------------------------------------- GPT
70 	LBA -33        |Entries 5 - 128                  |
73 	LBA -2         |                                 |
74 	--------------------------------------------------
75 	LBA -1         |Backup GPT Header                |
76 	----------------------------------------------------------
85 "LBA -1" means the last addressable block (in the mmc subsystem:
86 "dev_desc->lba - 1")
89 ----------------------------
100 40      8 B     First usable LBA for partitions (primary partition table last
102 48      8 B     Last usable LBA (secondary partition table first LBA - 1)
108 92      *       Reserved; must be ZERO (420 bytes for a 512-byte LBA)
118 and "Backup LBA" and therefore different CRC32 check-sum.
131 	   ----------------------
142 	   Bit 0  - System partition
143 	   Bit 1  - Hide from EFI
144 	   Bit 2  - Legacy BIOS bootable
145 	   Bit 48-63 - Defined and used by the individual partition type
147 	   Bit 60 - Read-only
148 	   Bit 62 - Hidden
149 	   Bit 63 - Not mount
151 Creating GPT partitions in U-Boot:
156    Format of partitions layout:
157      "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
171    non-existent environment variable. The environment variable will be set to
177      "name=u-boot,size=60MiB;name=boot,size=60Mib,bootable;name=rootfs,size=0"
179    "part list <interface> <dev> -bootable <varname>",
184 3. From u-boot prompt type:
185    gpt write mmc 0 $partitions
187 Checking (validating) GPT partitions in U-Boot:
192 At u-boot prompt one needs to write:
193    gpt verify mmc 0 [$partitions]
195 where [$partitions] is an optional parameter.
199 When provided, additionally partition data - name, size and starting
200 offset (last two in LBA) - are compared with data defined in '$partitions'
204 on non-volatile medium stored GPT.
208 U-BOOT> gpt verify mmc 0 $partitions
209 U-BOOT> if test $? = 0; then echo "GPT OK"; else echo "GPT ERR"; fi
211 Renaming GPT partitions from U-Boot:
214 GPT partition names are a mechanism via which userspace and U-Boot can
215 communicate about software updates and boot failure.  The 'gpt guid',
217 programmatic renaming of partitions from bootscripts by generating and
218 modifying the partitions layout string.  Here is an illustration of
221 U-BOOT> gpt swap mmc 0 primary backup
223 Afterwards, all partitions previously named 'primary' will be named
224 'backup', and vice-versa.  Alternatively, single partitions may be
228 U-BOOT> gpt rename mmc 0 1 primary
244 PARTITION_BASIC_DATA_GUID (EBD0A0A2-B9E5-4433-87C0-68B6B72699C7).
249      "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
251 	type=0FC63DAF-8483-4772-8E79-3D69D8477DE4;"
255 	           (C12A7328-F81F-11D2-BA4B-00A0C93EC93B)
257 	           (024DEE41-33E7-11D3-9D69-0008C781F39F)
259 	           (E3C9E316-0B5C-4DB8-817D-F92DF00215AE)
261 	            (EBD0A0A2-B9E5-4433-87C0-68B6B72699C7)
263 	           (0FC63DAF-8483-4772-8E79-3D69D8477DE4)
265 	           (A19D880F-05FC-4D3B-A006-743F0F84911E)
267 	           (0657FD6D-A4AB-43C4-84E5-0933C84B4F4F)
269 	           (E6D6D379-F507-44C2-A23C-238F2A3DF928)
271     "uuid_disk=...;name=u-boot,size=60MiB,uuid=...;
281 recovery. Both are able to handle GUID partitions.
282 Please, pay attention at -l switch for parted.
285 (-d switch) passed in UUID string. It can be used to generate partitions UUID
286 passed to u-boot environment variables.
294 Partitions layout can be printed by typing "mmc part". Note that each partition