Merge branch '2022-04-25-initial-implementation-of-stdboot'

To quote the author:
The bootflow feature provide a built-in way for U-Boot to automatically
boot an Operating System without custom scripting and other customisation.
This is called 'standard boot' since it provides a standard way for
U-Boot to boot a distro, without scripting.

It introduces the following concepts:

   - bootdev - a device which can hold a distro
   - bootmeth - a method to scan a bootdev to find bootflows (owned by
                U-Boot)
   - bootflow - a description of how to boot (owned by the distro)

This series provides an implementation of these, enabled to scan for
bootflows from MMC, USB and Ethernet. It supports the existing distro
boot as well as the EFI loader flow (bootefi/bootmgr). It works
similiarly to the existing script-based approach, but is native to
U-Boot.

With this we can boot on a Raspberry Pi 3 with just one command:

   bootflow scan -lb

which means to scan, listing (-l) each bootflow and trying to boot each
one (-b). The final patch shows this.

With a standard way to identify boot devices, booting become easier. It
also should be possible to support U-Boot scripts, for backwards
compatibility only.

...

The design is described in these two documents:

https://drive.google.com/file/d/1ggW0KJpUOR__vBkj3l61L2dav4ZkNC12/view?usp=sharing

https://drive.google.com/file/d/1kTrflO9vvGlKp-ZH_jlgb9TY3WYG6FF9/view?usp=sharing

1 files changed, 39 insertions, 0 deletions

diff --git a/cmd/Kconfig b/cmd/Kconfig
index 65517cb69e..2b575a2b42 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -211,6 +211,45 @@ config CMD_BOOTM_PRE_LOAD
 	 This stage allow to check or modify the image provided
 	 to the bootm command.
 
+config CMD_BOOTDEV
+	bool "bootdev"
+	depends on BOOTSTD
+	default y if BOOTSTD_FULL
+	help
+	  Support listing available bootdevs (boot devices) which can provide an
+	  OS to boot, as well as showing information about a particular one.
+
+	  This command is not necessary for bootstd to work.
+
+config CMD_BOOTFLOW
+	bool "bootflow"
+	depends on BOOTSTD
+	default y
+	help
+	  Support scanning for bootflows available with the bootdevs. The
+	  bootflows can optionally be booted.
+
+config CMD_BOOTFLOW_FULL
+	bool "bootflow - extract subcommands"
+	depends on BOOTSTD_FULL
+	default y if BOOTSTD_FULL
+	help
+	  Add the ability to list the available bootflows, select one and obtain
+	  information about it.
+
+	  This command is not necessary for bootstd to work.
+
+config CMD_BOOTMETH
+	bool "bootmeth"
+	depends on BOOTSTD
+	default y if BOOTSTD_FULL
+	help
+	  Support listing available bootmethds (methods used to boot an
+	  Operating System), as well as selecting the order that the bootmeths
+	  are used.
+
+	  This command is not necessary for bootstd to work.
+
 config BOOTM_EFI
 	bool "Support booting UEFI FIT images"
 	depends on CMD_BOOTEFI && CMD_BOOTM && FIT