On 08/24/2012 02:13 AM, Lukasz Majewski wrote:
Documentation of the GPT table format.
+++ b/doc/README.gpt
+Glossary: +======== +- UUID -(Universally Unique Identifier) +- GUID - (Globally Unique ID) +- EFI - (Extensible Firmware Interface) +- UEFI - (Unified EFI) - EFI evolution +- GPT (GUID Page Table) - it is the EFI standard part
GUID Partition Table, not Page.
+- partitions - lists of availavle partitions (defined at u-boot):
- ./include/configs/{target}.h
+Introduction: +============= +This document describes the GPT partition table format when used with u-boot.
+UUID introduction[5]: +====================
What is "[5]"?
+For instance, GUID of Linux data partition: EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 +For u-boot GPT hyphens are omitted.
I don't think U-Boot should omit any of the hyphens; it makes the UUIDs far more readable, and the strings can then be cut/paste to/from other applications that use/print UUIDs, without any manual conversion.
+Historically there are 5 methods to generate this number. The oldest one is +combining machine's MAC address and timer (epoch) value.
+Successive versions are using MD5 hash, random numbers and SHA-1 hash. All major +OSes and programming languages are providing libraries to compute UUID.
+However it costs in terms of the computational power and memory footprint. +Therefore u-boot uses the crc32 with reading random block (512B) from MMC +storage device to generate UUID/GUID.
That doesn't seem particularly relevant to general documentation about GPT; it's an implementation detail of the GPT creation command in a later patch, and could easily be changed.
In fact, I wonder why not require the user to concoct UUIDs and pass them to your GPT creation command, rather than forming them using some non-standard process.
+GUID brief explanation:
Not "GUID", but "GPT".
+======================
- Layout:
- LBA 0 |Protective MBR |
- LBA 1 |Primary GPT Header | Primary
- -------------------------------------------------- GPT
- LBA 2 |Entry 1|Entry 2| Entry 3| Entry 4|
- LBA 3 |Entries 5 - 128 |
| || |-----------------------------------------------------------LBA 34 |Partition 1 |
The indentation looks inconsistent in this diagram
| |-----------------------------------|Partition 2 || |-----------------------------------|Partition n || |
-----------------------------------------------------------LBA -34 |Entry 1|Entry 2| Entry 3| Entry 4| Secondary--------------------------------------------------- (bkp)LBA 34 |Partition 1 || |-----------------------------------|Partition 2 || |-----------------------------------|Partition n || |
That part of the diagram appears duplicated.
-----------------------------------------------------------LBA -34 |Entry 1|Entry 2| Entry 3| Entry 4| Secondary--------------------------------------------------- (bkp)LBA -33 |Entries 5 - 128 | GPT| || |LBA -2 | |---------------------------------------------------LBA -1 |Secondary GPT Header |-----------------------------------------------------------
Attribute flags (Don't used at u-boot):
I wouldn't write "Don't used at u-boot" since that's potentially subject to change. For example, I'm expecting to send a patch to use the "Legacy BIOS bootable" attribute soon.