From: Alison Chaiken alison@peloton-tech.com
One way for userspace and the bootloader to exchange information about dynamic image selection is via the storage device partition table, as described at
https://source.android.com/devices/tech/ota/ab_updates
The scheme described there relies on setting partitions' "boot" flag. When no partition on a device is bootable since the kernel and U-Boot are stored elsewhere, the name field in the GPT partition table offers another logical place to store information. These patches allow users to easily modify GPT partition names via bootscripts that can select different images based on a boot-failure counter, or when userspace installs a software update.
These patches have been (re)tested on a TI DRA7xx-based SOM with U-Boot 2015.07. The storage device is an eMMC.
Significant changes since v2: -- Got rid of the need to allocate memory for the GUID string in do_gpt(); -- Fixed the problems with string NULL termination in allocate_disk_part(); -- Removed duplicate definition of MAX_SEARCH_PARTITIONS from disk/part.c and increased the value in include/part.h to 64; -- Improved the commit message for "rename GPT partitions to detect boot failure" to better describe the version of the patch I submitted; -- Fixed numerous small problems with function return values.
Significant changes since v1: -- Put the gpt_flip() function and auxiliary ones inside a new CONFIG_CMD_GPT_FLIP option that depends on CMD_GPT. -- Replace intentional overwriting of name and type string arrays with memset() instead. -- Move part.h changes earlier in the patchset. -- Add a few lines to README.gpt about the new gpt subcommands.
Added a few simple patches to do the following: -- Replace remaining occurrences of '37' with UUID_STR_LEN+1; -- Introduce new macros to get rid of the similar '32'; -- fix a smaller error in doc/README.gpt.
There are also some fixups of whitespace and formatting errors (plus usual inevitable addition of new ones).
To do in future: -- Add support for preserving the type flag for partitions. The u-boot version on which this patchset is based did not have this feature, and it's easy to add, but I need to figure how to test it first.
-- Add tests for the new gpt commands to the sandbox.
Alison Chaiken (5): GPT: add accessor function for disk GUID partitions: increase MAX_SEARCH_PARTITIONS and move to part.h GPT: read partition table from device into a data structure rename GPT partitions to detect boot failure GPT: fix error in partitions string doc
cmd/Kconfig | 7 ++ cmd/gpt.c | 318 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ disk/part.c | 1 - disk/part_efi.c | 31 ++++++ doc/README.gpt | 24 ++++- include/part.h | 23 ++++ 6 files changed, 398 insertions(+), 6 deletions(-)