[PATCH v4 00/33] Initial implementation of standard boot

Tom Rini trini at konsulko.com
Wed Mar 23 15:05:00 CET 2022

On Sun, Mar 06, 2022 at 05:49:43AM -0700, Simon Glass wrote:
> 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.
> This series relies on the PXE clean-up series, posted here:
>    https://patchwork.ozlabs.org/project/uboot/list/?series=267078
> For documentation, see the 'doc' patch.
> For version 2, a new naming scheme is used as above:
>    - bootdev is used instead of bootdevice, because 'device' is overused,
>        is everywhere in U-Boot, can be confused with udevice
>    - bootmeth - because 'method' is too vanilla, appears 1300 times in
>        U-Boot
> Also in version 2, drivers are introduced for the boot methods, to make
> it more extensible. Booting a custom OS is simply a matter of creating a
> bootmeth for it and implementing the read_file() and boot() methods.
> Version 4 makes some minor improvements and leaves out the RFC patch for
> rpi conversion, in the hope of getting the base support applied sooner
> rather than later.
> 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

I keep putting off commenting more here, but, I still feel this is the
wrong direction.  What problems do we have today with distro boot?
Well, we haven't figured out how to move configuring it out of the board
config.h file.  But that's just one of a half dozen or so examples of
how we haven't figured out a good solution to configuring the default
environment.  And only some of those other examples are boot related
(the NXP chain of trust booting stuff is another boot example, ETHPRIME,
HOSTNAME, etc, are non-boot examples).

We also aren't improving testing of "can we boot" here, because what
THAT needs is setting up LAVA and booting some installers on some
hardware (and some QEMU).  That's testing that Linux boot works.  Today
we have tests for hush parsing, and if distro boot makes use of
something we don't have a test for, we need a test for it.  This adds
tests for itself, which is good.

And I still don't see an example of where this demonstrates that
existing non-UEFI boot cases are now easier to handle or cleaner to
handle or otherwise better.

In that this is an attempt to tackle one of the long standing needed
migrations (be able to drop board config.h files), something here needs
doing.  But I don't see this as the right direction, sorry.

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