[PATCH 5/6] bootstd: Add a bootmeth for Android
Igor Opaniuk
igor.opaniuk at gmail.com
Mon Jun 10 17:15:48 CEST 2024
Hi Mattijs,
On Thu, Jun 6, 2024 at 2:24 PM Mattijs Korpershoek
<mkorpershoek at baylibre.com> wrote:
>
> Android boot flow is a bit different than a regular Linux distro.
> Android relies on multiple partitions in order to boot.
>
> A typical boot flow would be:
> 1. Parse the Bootloader Control Block (BCB, misc partition)
> 2. If BCB requested bootonce-bootloader, start fastboot and wait.
> 3. If BCB requested recovery or normal android, run the following:
> 3.a. Get slot (A/B) from BCB
> 3.b. Run AVB (Android Verified Boot) on boot partitions
> 3.c. Load boot and vendor_boot partitions
> 3.d. Load device-tree, ramdisk and boot
>
> The AOSP documentation has more details at [1], [2], [3]
>
> This has been implemented via complex boot scripts such as [4].
> However, these boot script are neither very maintainable nor generic.
> Moreover, DISTRO_DEFAULTS is being deprecated [5].
>
> Add a generic Android bootflow implementation for bootstd.
> For this initial version, only boot image v4 is supported.
>
> [1] https://source.android.com/docs/core/architecture/bootloader
> [2] https://source.android.com/docs/core/architecture/partitions
> [3] https://source.android.com/docs/core/architecture/partitions/generic-boot
> [4] https://source.denx.de/u-boot/u-boot/-/blob/master/include/configs/meson64_android.h
> [5] https://lore.kernel.org/r/all/20230914165615.1058529-17-sjg@chromium.org/
>
> Signed-off-by: Mattijs Korpershoek <mkorpershoek at baylibre.com>
> ---
> MAINTAINERS | 7 +
> boot/Kconfig | 14 ++
> boot/Makefile | 2 +
> boot/bootmeth_android.c | 522 ++++++++++++++++++++++++++++++++++++++++++++++++
> boot/bootmeth_android.h | 27 +++
> doc/develop/bootstd.rst | 6 +
> 6 files changed, 578 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 66783d636e3d..6d2b87720565 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -939,6 +939,13 @@ F: include/bootstd.h
> F: net/eth_bootdevice.c
> F: test/boot/
>
> +BOOTMETH_ANDROID
> +M: Mattijs Korpershoek <mkorpershoek at baylibre.com>
> +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
> +
> BTRFS
> M: Marek Behún <kabel at kernel.org>
> R: Qu Wenruo <wqu at suse.com>
> diff --git a/boot/Kconfig b/boot/Kconfig
> index 6f3096c15a6f..5fa6f3b8315d 100644
> --- a/boot/Kconfig
> +++ b/boot/Kconfig
> @@ -494,6 +494,20 @@ config BOOTMETH_GLOBAL
> EFI bootmgr, since they take full control over which bootdevs are
> selected to boot.
>
> +config BOOTMETH_ANDROID
> + bool "Bootdev support for Android"
> + depends on X86 || ARM || SANDBOX
> + select ANDROID_AB
> + select ANDROID_BOOT_IMAGE
> + select CMD_BCB
> + select PARTITION_TYPE_GUID
> + select PARTITION_UUIDS
> + help
> + Enables support for booting Android using bootdevs. Android requires
> + multiple partitions (misc, boot, vbmeta, ...) in storage for booting.
> +
> + Note that only MMC bootdevs are supported at present.
> +
> config BOOTMETH_CROS
> bool "Bootdev support for Chromium OS"
> depends on X86 || ARM || SANDBOX
> diff --git a/boot/Makefile b/boot/Makefile
> index 84ccfeaecec4..75d1cd46fabf 100644
> --- a/boot/Makefile
> +++ b/boot/Makefile
> @@ -66,3 +66,5 @@ obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_REQUEST) += vbe_request.o
> obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE) += vbe_simple.o
> obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE_FW) += vbe_simple_fw.o
> obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_VBE_SIMPLE_OS) += vbe_simple_os.o
> +
> +obj-$(CONFIG_$(SPL_TPL_)BOOTMETH_ANDROID) += bootmeth_android.o
> diff --git a/boot/bootmeth_android.c b/boot/bootmeth_android.c
> new file mode 100644
> index 000000000000..26d548d2fd6e
> --- /dev/null
> +++ b/boot/bootmeth_android.c
> @@ -0,0 +1,522 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Bootmethod for Android
> + *
> + * Copyright (C) 2024 BayLibre, SAS
> + * Written by Mattijs Korpershoek <mkorpershoek at baylibre.com>
> + */
> +#define LOG_CATEGORY UCLASS_BOOTSTD
> +
> +#include <android_ab.h>
> +#include <android_image.h>
> +#if CONFIG_IS_ENABLED(AVB_VERIFY)
> +#include <avb_verify.h>
> +#endif
> +#include <bcb.h>
> +#include <blk.h>
> +#include <bootflow.h>
> +#include <bootm.h>
> +#include <bootmeth.h>
> +#include <dm.h>
> +#include <image.h>
> +#include <malloc.h>
> +#include <mapmem.h>
> +#include <part.h>
> +#include "bootmeth_android.h"
> +
> +#define BCB_FIELD_COMMAND_SZ 32
> +#define BCB_PART_NAME "misc"
> +#define BOOT_PART_NAME "boot"
> +#define VENDOR_BOOT_PART_NAME "vendor_boot"
> +
> +/**
> + * struct android_priv - Private data
> + *
> + * This is read from the disk and recorded for use when the full Android
> + * kernel must be loaded and booted
> + */
> +struct android_priv {
> + int boot_mode;
> + char slot[2];
> + u32 header_version;
> +};
> +
> +static int android_check(struct udevice *dev, struct bootflow_iter *iter)
> +{
> + /* This only works on mmc devices */
> + if (bootflow_iter_check_mmc(iter))
> + return log_msg_ret("mmc", -ENOTSUPP);
> +
> + /* This only works on whole devices, as multiple
> + * partitions are needed to boot Android
> + */
Please use Linux kernel coding style for long comments [1].
Same in all occurrences below
[1] https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting
> + if (iter->part != 0)
> + return log_msg_ret("mmc part", -ENOTSUPP);
> +
> + return 0;
> +}
> +
> +static int scan_boot_part(struct udevice *blk, struct android_priv *priv)
> +{
> + struct blk_desc *desc = dev_get_uclass_plat(blk);
> + struct disk_partition partition;
> + char partname[PART_NAME_LEN];
> + ulong num_blks, bufsz;
> + char *buf;
> + int ret;
> +
> + sprintf(partname, BOOT_PART_NAME "_%s", priv->slot);
> + ret = part_get_info_by_name(desc, partname, &partition);
> + if (ret < 0)
> + return log_msg_ret("part info", ret);
> +
> + num_blks = DIV_ROUND_UP(sizeof(struct andr_boot_img_hdr_v0), desc->blksz);
> + bufsz = num_blks * desc->blksz;
> + buf = malloc(bufsz);
> + if (!buf)
> + return log_msg_ret("buf", -ENOMEM);
> +
> + ret = blk_read(blk, partition.start, num_blks, buf);
> + if (ret != num_blks) {
> + free(buf);
> + return log_msg_ret("part read", -EIO);
> + }
> +
> + if (!is_android_boot_image_header(buf)) {
> + free(buf);
> + return log_msg_ret("header", -ENOENT);
> + }
> +
> + priv->header_version = android_image_get_version(buf);
> +
> + return 0;
Shouldn't we free(buf) also here?
> +}
> +
> +static int scan_vendor_boot_part(struct udevice *blk, const char slot[2])
> +{
> + struct blk_desc *desc = dev_get_uclass_plat(blk);
> + struct disk_partition partition;
> + char partname[PART_NAME_LEN];
> + ulong num_blks, bufsz;
> + char *buf;
> + int ret;
> +
> + sprintf(partname, VENDOR_BOOT_PART_NAME "_%s", slot);
> + ret = part_get_info_by_name(desc, partname, &partition);
> + if (ret < 0)
> + return log_msg_ret("part info", ret);
> +
> + num_blks = DIV_ROUND_UP(sizeof(struct andr_vnd_boot_img_hdr), desc->blksz);
> + bufsz = num_blks * desc->blksz;
> + buf = malloc(bufsz);
> + if (!buf)
> + return log_msg_ret("buf", -ENOMEM);
> +
> + ret = blk_read(blk, partition.start, num_blks, buf);
> + if (ret != num_blks) {
> + free(buf);
> + return log_msg_ret("part read", -EIO);
> + }
> +
> + if (!is_android_vendor_boot_image_header(buf)) {
> + free(buf);
> + return log_msg_ret("header", -ENOENT);
> + }
> +
> + return 0;
free(buf)?
> +}
> +
> +static int android_read_slot_from_bcb(struct bootflow *bflow, bool decrement)
> +{
> + struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
> + struct android_priv *priv = bflow->bootmeth_priv;
> + struct disk_partition misc;
> + char slot_suffix[3];
> + int ret;
> +
> + ret = part_get_info_by_name(desc, BCB_PART_NAME, &misc);
> + if (ret < 0)
> + return log_msg_ret("part", ret);
> +
> + ret = ab_select_slot(desc, &misc, decrement);
> + if (ret < 0)
> + return log_msg_ret("slot", ret);
> +
> + priv->slot[0] = BOOT_SLOT_NAME(ret);
> + priv->slot[1] = '\0';
> +
> + sprintf(slot_suffix, "_%s", priv->slot);
> + ret = bootflow_cmdline_set_arg(bflow, "androidboot.slot_suffix",
> + slot_suffix, false);
> + if (ret < 0)
> + return log_msg_ret("slot", ret);
> +
> + return 0;
> +}
> +
> +static int configure_serialno(struct bootflow *bflow)
> +{
> + char *serialno = env_get("serial#");
> +
> + if (!serialno)
> + return log_msg_ret("serial", -ENOENT);
> +
> + return bootflow_cmdline_set_arg(bflow, "androidboot.serialno", serialno, false);
> +}
> +
> +static int android_read_bootflow(struct udevice *dev, struct bootflow *bflow)
> +{
> + struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
> + struct disk_partition misc;
> + struct android_priv *priv;
> + char command[BCB_FIELD_COMMAND_SZ];
> + int ret;
> +
> + bflow->state = BOOTFLOWST_MEDIA;
> +
> + /* bcb_find_partition_and_load() will print errors to stdout
> + * if BCB_PART_NAME is not found. To avoid that, check if the
> + * partition exists first.
> + */
> + ret = part_get_info_by_name(desc, BCB_PART_NAME, &misc);
> + if (ret < 0)
> + return log_msg_ret("part", ret);
> +
> + ret = bcb_find_partition_and_load("mmc", desc->devnum, BCB_PART_NAME);
> + if (ret < 0)
> + return log_msg_ret("bcb load", ret);
> +
> + ret = bcb_get(BCB_FIELD_COMMAND, command, sizeof(command));
> + if (ret < 0)
> + return log_msg_ret("bcb read", ret);
> +
> + priv = malloc(sizeof(struct android_priv));
> + if (!priv)
> + return log_msg_ret("buf", -ENOMEM);
> +
> + bflow->bootmeth_priv = priv;
Probably we should do that just before successfully returning from the function,
otherwise we will end up with a dangling pointer.
> + if (!strcmp("bootonce-bootloader", command)) {
> + priv->boot_mode = ANDROID_BOOT_MODE_BOOTLOADER;
> + bflow->os_name = strdup("Android (bootloader)");
> + } else if (!strcmp("boot-fastboot", command)) {
> + priv->boot_mode = ANDROID_BOOT_MODE_RECOVERY;
> + bflow->os_name = strdup("Android (fastbootd)");
> + } else if (!strcmp("boot-recovery", command)) {
> + priv->boot_mode = ANDROID_BOOT_MODE_RECOVERY;
> + bflow->os_name = strdup("Android (recovery)");
> + } else {
> + priv->boot_mode = ANDROID_BOOT_MODE_NORMAL;
> + bflow->os_name = strdup("Android");
> + }
> + if (!bflow->os_name)
> + return log_msg_ret("os", -ENOMEM);
> +
> + if (priv->boot_mode == ANDROID_BOOT_MODE_BOOTLOADER) {
> + /* Clear BCB */
> + memset(command, 0, sizeof(command));
> + ret = bcb_set(BCB_FIELD_COMMAND, command);
> + if (ret < 0) {
> + free(priv);
> + return log_msg_ret("bcb set", ret);
> + }
> + ret = bcb_store();
> + if (ret < 0) {
> + free(priv);
> + return log_msg_ret("bcb store", ret);
> + }
> +
is free(bflow->bootmeth_priv) handled in functions that call
android_read_bootflow() ?
> + bflow->state = BOOTFLOWST_READY;
> + return 0;
> + }
> +
> + /* For recovery and normal boot, we need to scan the partitions */
> + ret = android_read_slot_from_bcb(bflow, false);
> + if (ret < 0) {
> + free(priv);
> + return log_msg_ret("read slot", ret);
> + }
> +
> + ret = scan_boot_part(bflow->blk, priv);
> + if (ret < 0) {
> + printf("- scan boot failed: err=%d\n", ret);
> + free(priv);
> + return log_msg_ret("scan boot", ret);
> + }
> +
> + if (priv->header_version != 4) {
> + printf("- Only boot.img v4 is supported\n");
> + free(priv);
> + return log_msg_ret("version", -EINVAL);
> + }
> +
> + ret = scan_vendor_boot_part(bflow->blk, priv->slot);
> + if (ret < 0) {
> + printf("- scan vendor_boot failed: err=%d\n", ret);
> + free(priv);
> + return log_msg_ret("scan vendor_boot", ret);
> + }
> +
> + /* Ignoring return code: setting serial number is not mandatory for booting */
> + configure_serialno(bflow);
> +
> + if (priv->boot_mode == ANDROID_BOOT_MODE_NORMAL) {
> + ret = bootflow_cmdline_set_arg(bflow, "androidboot.force_normal_boot", "1", false);
> + if (ret < 0) {
> + free(priv);
> + return log_msg_ret("normal_boot", ret);
> + }
> + }
> +
> + bflow->state = BOOTFLOWST_READY;
> +
> + return 0;
> +}
> +
> +static int android_read_file(struct udevice *dev, struct bootflow *bflow,
> + const char *file_path, ulong addr, ulong *sizep)
> +{
> + /* Reading individual files is not supported since we only
> + * operate on whole mmc devices (because we require multiple partitions)
> + */
> + return log_msg_ret("Unsupported", -ENOSYS);
> +}
> +
> +static int read_slotted_partition(struct blk_desc *desc, const char *const name,
> + const char slot[2], ulong addr)
> +{
> + struct disk_partition partition;
> + char partname[PART_NAME_LEN];
> + int ret;
> + u32 n;
> +
> + /* Ensure name fits in partname it should be: <name>_<slot>\0 */
> + if (strlen(name) > (PART_NAME_LEN - 2 - 1))
> + return log_msg_ret("name too long", -EINVAL);
> +
> + sprintf(partname, "%s_%s", name, slot);
> + ret = part_get_info_by_name(desc, partname, &partition);
> + if (ret < 0)
> + return log_msg_ret("part", ret);
> +
> + n = blk_dread(desc, partition.start, partition.size, map_sysmem(addr, 0));
> + if (n < partition.size)
> + return log_msg_ret("part read", -EIO);
> +
> + return 0;
> +}
> +
> +#if CONFIG_IS_ENABLED(AVB_VERIFY)
> +static int avb_append_commandline_arg(struct bootflow *bflow, char *arg)
> +{
> + char *key = strsep(&arg, "=");
> + char *value = arg;
> + int ret;
> +
> + ret = bootflow_cmdline_set_arg(bflow, key, value, false);
> + if (ret < 0)
> + return log_msg_ret("avb cmdline", ret);
> +
> + return 0;
> +}
> +
> +static int avb_append_commandline(struct bootflow *bflow, char *cmdline)
> +{
> + char *arg = strsep(&cmdline, " ");
> + int ret;
> +
> + while (arg) {
> + ret = avb_append_commandline_arg(bflow, arg);
> + if (ret < 0)
> + return ret;
> +
> + arg = strsep(&cmdline, " ");
> + }
> +
> + return 0;
> +}
> +
> +static int run_avb_verification(struct bootflow *bflow)
> +{
> + struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
> + struct android_priv *priv = bflow->bootmeth_priv;
> + const char * const requested_partitions[] = {"boot", "vendor_boot"};
> + struct AvbOps *avb_ops;
> + AvbSlotVerifyResult result;
> + AvbSlotVerifyData *out_data;
> + enum avb_boot_state boot_state;
> + char *extra_args;
> + char slot_suffix[3];
> + bool unlocked = false;
> + int ret;
> +
> + avb_ops = avb_ops_alloc(desc->devnum);
> + if (!avb_ops)
> + return log_msg_ret("avb ops", -ENOMEM);.
> +
> + sprintf(slot_suffix, "_%s", priv->slot);
> +
> + ret = avb_ops->read_is_device_unlocked(avb_ops, &unlocked);
> + if (ret != AVB_IO_RESULT_OK)
> + return log_msg_ret("avb lock", -EIO);
> +
> + result = avb_slot_verify(avb_ops,
> + requested_partitions,
> + slot_suffix,
> + unlocked,
> + AVB_HASHTREE_ERROR_MODE_RESTART_AND_INVALIDATE,
> + &out_data);
> +
> + if (result != AVB_SLOT_VERIFY_RESULT_OK) {
> + printf("Verification failed, reason: %s\n",
> + str_avb_slot_error(result));
avb_ops_free(avb_ops) ?
> + return log_msg_ret("avb verify", -EIO);
> + }
> +
> + if (unlocked)
> + boot_state = AVB_ORANGE;
> + else
> + boot_state = AVB_GREEN;
> +
> + extra_args = avb_set_state(avb_ops, boot_state);
> + if (extra_args) {
> + ret = avb_append_commandline_arg(bflow, extra_args);
> + if (ret < 0)
> + goto free_out_data;
> + }
> +
> + ret = avb_append_commandline(bflow, out_data->cmdline);
> + if (ret < 0)
> + goto free_out_data;
> +
> + return 0;
> +
> + free_out_data:
> + if (out_data)
> + avb_slot_verify_data_free(out_data);
> +
> + return log_msg_ret("avb cmdline", ret);
> +}
> +#else
> +static int run_avb_verification(struct bootflow *bflow)
> +{
> + int ret;
> +
> + /* When AVB is unsupported, pass ORANGE state */
> + ret = bootflow_cmdline_set_arg(bflow,
> + "androidboot.verifiedbootstate",
> + "orange", false);
> + if (ret < 0)
> + return log_msg_ret("avb cmdline", ret);
> +
> + return 0;
> +}
> +#endif /* AVB_VERIFY */
> +
> +static int boot_android_normal(struct bootflow *bflow)
> +{
> + struct blk_desc *desc = dev_get_uclass_plat(bflow->blk);
> + struct android_priv *priv = bflow->bootmeth_priv;
> + int ret;
> +
> + ulong loadaddr = env_get_hex("loadaddr", 0);
> + ulong vloadaddr = env_get_hex("vendor_boot_comp_addr_r", 0);
> +
> + ret = run_avb_verification(bflow);
> + if (ret < 0)
> + return log_msg_ret("avb", ret);
> +
> + /* Read slot once more to decrement counter from BCB */
> + ret = android_read_slot_from_bcb(bflow, true);
> + if (ret < 0)
> + return log_msg_ret("read slot", ret);
> +
> + ret = read_slotted_partition(desc, "boot", priv->slot, loadaddr);
> + if (ret < 0)
> + return log_msg_ret("read boot", ret);
> +
> + ret = read_slotted_partition(desc, "vendor_boot", priv->slot, vloadaddr);
> + if (ret < 0)
> + return log_msg_ret("read vendor_boot", ret);
> +
> + set_abootimg_addr(loadaddr);
> + set_avendor_bootimg_addr(vloadaddr);
> +
> + ret = bootm_boot_start(loadaddr, bflow->cmdline);
> +
> + return log_msg_ret("boot", ret);
> +}
> +
> +static int boot_android_recovery(struct bootflow *bflow)
> +{
> + int ret;
> +
> + ret = boot_android_normal(bflow);
> +
> + return log_msg_ret("boot", ret);
> +}
> +
> +static int boot_android_bootloader(struct bootflow *bflow)
> +{
> + int ret;
> +
> + ret = run_command("fastboot usb 0", 0);
select CMD_FASTBOOT in Kconfig (config BOOTMETH_ANDROID)?
> + do_reset(NULL, 0, 0, NULL);
> +
> + return log_msg_ret("boot", ret);
> +}
> +
> +static int android_boot(struct udevice *dev, struct bootflow *bflow)
> +{
> + struct android_priv *priv = bflow->bootmeth_priv;
> + int ret;
> +
> + switch (priv->boot_mode) {
> + case ANDROID_BOOT_MODE_NORMAL:
> + ret = boot_android_normal(bflow);
> + break;
> + case ANDROID_BOOT_MODE_RECOVERY:
> + ret = boot_android_recovery(bflow);
> + break;
> + case ANDROID_BOOT_MODE_BOOTLOADER:
> + ret = boot_android_bootloader(bflow);
> + break;
> + default:
> + printf("ANDROID: Unknown boot mode %d. Running fastboot...\n",
> + priv->boot_mode);
> + boot_android_bootloader(bflow);
> + /* Tell we failed to boot since boot mode is unknown */
> + ret = -EFAULT;
> + }
> +
> + return ret;
> +}
> +
> +static int android_bootmeth_bind(struct udevice *dev)
> +{
> + struct bootmeth_uc_plat *plat = dev_get_uclass_plat(dev);
> +
> + plat->desc = "Android boot";
> + plat->flags = BOOTMETHF_ANY_PART;
> +
> + return 0;
> +}
> +
> +static struct bootmeth_ops android_bootmeth_ops = {
> + .check = android_check,
> + .read_bootflow = android_read_bootflow,
> + .read_file = android_read_file,
> + .boot = android_boot,
> +};
> +
> +static const struct udevice_id android_bootmeth_ids[] = {
> + { .compatible = "u-boot,android" },
> + { }
> +};
> +
> +U_BOOT_DRIVER(bootmeth_android) = {
> + .name = "bootmeth_android",
> + .id = UCLASS_BOOTMETH,
> + .of_match = android_bootmeth_ids,
> + .ops = &android_bootmeth_ops,
> + .bind = android_bootmeth_bind,
> +};
> diff --git a/boot/bootmeth_android.h b/boot/bootmeth_android.h
> new file mode 100644
> index 000000000000..411c2f2d15e7
> --- /dev/null
> +++ b/boot/bootmeth_android.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * Bootmethod for Android
> + *
> + * Copyright (C) 2024 BayLibre, SAS
> + * Written by Mattijs Korpershoek <mkorpershoek at baylibre.com>
> + */
> +
> +enum android_boot_mode {
> + ANDROID_BOOT_MODE_NORMAL = 0,
> +
> + /* Android "recovery" is a special boot mode that uses another ramdisk.
> + * It can be used to "factory reset" a board or to flash logical partitions
> + * It operates in 2 modes: adb or fastbootd
> + * To enter recovery from Android, we can do:
> + * $ adb reboot recovery
> + * $ adb reboot fastboot
> + */
> + ANDROID_BOOT_MODE_RECOVERY,
> +
> + /* Android "bootloader" is for accessing/reflashing physical partitions
> + * Typically, this will launch a fastboot process in U-Boot.
> + * To enter "bootloader" from Android, we can do:
> + * $ adb reboot bootloader
> + */
> + ANDROID_BOOT_MODE_BOOTLOADER,
> +};
> diff --git a/doc/develop/bootstd.rst b/doc/develop/bootstd.rst
> index a07a72581e7a..709fa9e64ff3 100644
> --- a/doc/develop/bootstd.rst
> +++ b/doc/develop/bootstd.rst
> @@ -95,6 +95,7 @@ bootflows.
>
> Note: it is possible to have a bootmeth that uses a partition or a whole device
> directly, but it is more common to use a filesystem.
> +For example, the Android bootmeth uses a whole device.
>
> Note that some bootmeths are 'global', meaning that they select the bootdev
> themselves. Examples include VBE and EFI boot manager. In this case, they
> @@ -277,6 +278,9 @@ script_offset_f
> script_size_f
> Size of the script to load, e.g. 0x2000
>
> +vendor_boot_comp_addr_r
> + Address to which to load the vendor_boot Android image, e.g. 0xe0000000
> +
> Some variables are set by script bootmeth:
>
> devtype
> @@ -418,6 +422,7 @@ Bootmeth drivers are provided for:
> - EFI boot using bootefi from disk
> - VBE
> - EFI boot using boot manager
> + - Android bootflow (boot image v4)
>
>
> Command interface
> @@ -786,6 +791,7 @@ To do
> Some things that need to be done to completely replace the distro-boot scripts:
>
> - implement extensions (devicetree overlays with add-on boards)
> +- implement legacy (boot image v2) android boot flow
>
> Other ideas:
>
>
> --
> 2.45.0
>
Some comments after a quick "scan". Will take a more detailed look a
bit later today/tomorrow.
--
Best regards - Atentamente - Meilleures salutations
Igor Opaniuk
mailto: igor.opaniuk at gmail.com
skype: igor.opanyuk
https://www.linkedin.com/in/iopaniuk
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