From 70142d9ec08ab12cdc273767ec45575bd84bf4e9 Mon Sep 17 00:00:00 2001 From: Heinrich Schuchardt Date: Fri, 5 May 2023 17:14:26 +0200 Subject: [PATCH] Recommend usage of partition type GUIDs to find firmware If the firmware is loaded from a GPT partitioned medium, it should use the partition type GUID (and not sector number or partition number) to identify the relevant partition. This GUID should be unique for each board type. Signed-off-by: Heinrich Schuchardt --- source/chapter4-firmware-media.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/source/chapter4-firmware-media.rst b/source/chapter4-firmware-media.rst index b026e9f..bf0c1f9 100644 --- a/source/chapter4-firmware-media.rst +++ b/source/chapter4-firmware-media.rst @@ -117,6 +117,13 @@ non-protective partitions). There are no requirements on the contents or layout of the firmware protective partition. +Devices should use the partition type GUID to identify the partition with +the firmware to load. This is preferable over fixed sector or partition +numbers as it imposes the least restrictions on the partitioning scheme. + +Firmware partition type GUIDs should be unique for a board type. This +allows creating media that can be booted on a multitude of boards. + Placing GPT data structures away from firmware images can be accomplished by adjusting the GUID Partition Entry array location (adjusting the values of `PartitionEntryLBA` and `NumberOfPartitionEntries`,