From: Simon Glass sjg@chromium.org Date: Sun, 6 Mar 2022 05:49:43 -0700
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.
For the record. In its current state this series breaks booting on Apple M1:
Hit any key to stop autoboot: 0 Flags not supported: enable CONFIG_BOOTFLOW_FULL bootflow - Boot flows
Usage: bootflow scan - boot first available bootflow
=>
I'll see if I can actually convert this board to "standard boot". But I think this means that this breaks the majority of the boards currently in the tree.