wic: Add gpt-hybrid partition layout

Add support for formatting a disk with a hybrid MBR & GPT partition
scheme. In this scheme, the primary partitioning method is GPT, but a
valid MBR header is also written than can point to a subset of the GPT
partitions on the disk (any partitions marked with the `--mbr` flag will
be included in this MBR). The primary purpose of this method is to allow
for SoCs that can only find a bootloader in an MBR partition to use GPT
once the bootloader is running. As an example, older versions of the
Raspberry Pi firmware can only parse MBR partitions to find a kernel (or
other bootloader like u-boot), but once those have booted GPT partitions
can be used.

In addition to the partitions annotated with the `--mbr`, a "protective"
GPT partition of type 0xEE is added, as the existence of such a
partition is the indication to tooling that this a hybrid MBR and that
the GPT partition table should be parsed instead.

(From OE-Core rev: e50e4c2a5ada6947b3503ca4d8e9c30d359e8a5d)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/scripts/lib/wic/partition.py b/scripts/lib/wic/partition.py
index f11c393df5..b1a2306dd1 100644
--- a/scripts/lib/wic/partition.py
+++ b/scripts/lib/wic/partition.py
@@ -60,6 +60,7 @@ class Partition():
         self.has_fstab = False
         self.update_fstab_in_rootfs = False
         self.hidden = args.hidden
+        self.mbr = args.mbr
 
         self.lineno = lineno
         self.source_file = ""