[PATCH] doc: Add a description for bootmeth_android
Mattijs Korpershoek
mkorpershoek at baylibre.com
Wed Jul 24 14:41:25 CEST 2024
Add initial documentation for the Android bootmeth.
Signed-off-by: Mattijs Korpershoek <mkorpershoek at baylibre.com>
---
MAINTAINERS | 1 +
doc/develop/bootstd/android.rst | 39 +++++++++++++++++++++++++++++++++++++++
doc/develop/bootstd/index.rst | 1 +
doc/develop/bootstd/overview.rst | 2 +-
4 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/MAINTAINERS b/MAINTAINERS
index a6e47e8a2179..c2832345ab18 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -945,6 +945,7 @@ S: Maintained
T: git https://source.denx.de/u-boot/custodians/u-boot-dfu.git
F: boot/bootmeth_android.c
F: boot/bootmeth_android.h
+F: doc/develop/bootstd/android.rst
BTRFS
M: Marek Behún <kabel at kernel.org>
diff --git a/doc/develop/bootstd/android.rst b/doc/develop/bootstd/android.rst
new file mode 100644
index 000000000000..41701d5bdff3
--- /dev/null
+++ b/doc/develop/bootstd/android.rst
@@ -0,0 +1,39 @@
+.. SPDX-License-Identifier: GPL-2.0+:
+
+Android Bootmeth
+================
+
+Android provides a mechanism for booting its Operating System from eMMC storage,
+described on `source.android.com <https://source.android.com/docs/core/architecture/bootloader>`_.
+
+Android has strong requirements about partitioning layout which are described
+`here <https://source.android.com/docs/core/architecture/partitions>`_.
+Because multiple partitions are required, this bootmeth only operates on whole mmc
+devices which have a valid partition table.
+
+When invoked on a bootdev, this bootmeth searches for the ``misc`` partition in order
+to read the *boot mode*, which can be one of following:
+
+Normal
+ Boot the regular Android Operating System.
+
+Recovery
+ Boot a slimmed down Recovery Operating System. Can be used
+ to factory reset the device or to apply system updates.
+
+Bootloader
+ Stay in U-Boot and wait for fastboot commands from the host.
+
+After the *boot mode* has been determined, this bootmeth will read the *slot suffix*
+from the ``misc`` partition. For details about slots, see
+`the AOSP documentation <https://source.android.com/docs/core/ota/ab#slots>`_.
+
+When both the *boot mode* and the *slot suffix* are known, the bootflow is created.
+
+When the bootflow is booted, the bootmeth reads the kernel, the boot arguments and
+the vendor ramdisk.
+It then boots the kernel using bootm. The relevant devicetree blob is extracted
+from the ``boot`` partition based on the ``adtb_idx`` environment variable.
+
+The compatible string "u-boot,android" is used for the driver. It is present
+if `CONFIG_BOOTMETH_ANDROID` is enabled.
diff --git a/doc/develop/bootstd/index.rst b/doc/develop/bootstd/index.rst
index 9d35b567d55d..4c4e26ccdb70 100644
--- a/doc/develop/bootstd/index.rst
+++ b/doc/develop/bootstd/index.rst
@@ -10,6 +10,7 @@ Standard Boot
extlinux
pxelinux
qfw
+ android
cros
script
sandbox
diff --git a/doc/develop/bootstd/overview.rst b/doc/develop/bootstd/overview.rst
index ff3cc48eb64f..c6f003851b2a 100644
--- a/doc/develop/bootstd/overview.rst
+++ b/doc/develop/bootstd/overview.rst
@@ -429,7 +429,7 @@ Available bootmeth drivers
Bootmeth drivers are provided for booting from various media:
- - Android bootflow (boot image v4)
+ - :doc:`Android <android>` bootflow (boot image v4)
- :doc:`ChromiumOS <cros>` ChromiumOS boot from a disk
- EFI boot using bootefi from disk
- EFI boot using boot manager
---
base-commit: f659ba43837e5ae5a35fdff3736c8e13f9062abd
change-id: 20240724-doc-bootstd-android-ddf081b3622a
Best regards,
--
Mattijs Korpershoek <mkorpershoek at baylibre.com>
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