mirror of
https://github.com/u-boot/u-boot.git
synced 2025-04-23 05:08:24 +00:00
93767c5a8f
Add initial documentation for the Android bootmeth. Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com> Reviewed-by: Simon Glass <sjg@chromium.org>
39 lines
1.6 KiB
ReStructuredText
39 lines
1.6 KiB
ReStructuredText
.. 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.
|