Hi Tom,
On Wed, 23 Mar 2022 at 08:05, Tom Rini trini@konsulko.com wrote:
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=s...
https://drive.google.com/file/d/1kTrflO9vvGlKp-ZH_jlgb9TY3WYG6FF9/view?usp=s...
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.
Does anyone have a better idea for all of this? This is a solid base we can build on but we can't make any progress while this is just patches. What not apply it and we can move forward?
- solves the env problem for distro boot in that we don't need the scripts - gets rid of the scripts which are a confusing mess - provides proper high-level concepts of boot device and boot method - allows testing of the U-Boot part of 'can we boot' because we have tests for all the cases - we can expand this over time - allows non-UEFI boot cases like Chrome OS, which is currently just a hack for one board[1] - provides a programmatic base for A/B boot, etc.
I feel the same way with Takahiro's series, which has been out-of-tree for too long.
Please reconsider this. What do we have to lose?
Regards, Simon
[1] CONFIG_BOOTCOMMAND="tpm init; tpm startup TPM2_SU_CLEAR; read mmc 0:2 100000 0 80; setexpr loader *001004f0; setexpr size *00100518; setexpr blocks $size / 200; read mmc 0:2 100000 80 $blocks; setexpr setup $loader - 1000; setexpr cmdline_ptr $loader - 2000; setexpr.s cmdline *$cmdline_ptr; setexpr cmdline gsub %U \\${uuid}; if part uuid mmc 0:2 uuid; then zboot start 100000 0 0 0 $setup cmdline; zboot load; zboot setup; zboot dump; zboot go;fi"