On Tue, 24 Aug 2021 12:22:42 +0200 (CEST) Mark Kettenis <mark.kette...@xs4all.nl> wrote:
> > Date: Mon, 23 Aug 2021 16:01:46 -0400 > > From: Tom Rini <tr...@konsulko.com> > > > > On Mon, Aug 23, 2021 at 11:25:42AM -0600, Simon Glass wrote: > > > Hi Mark, > > > > > > On Mon, 23 Aug 2021 at 05:54, Mark Kettenis <mark.kette...@xs4all.nl> > > > wrote: > > > > > > > > > From: Simon Glass <s...@chromium.org> > > > > > Date: Wed, 18 Aug 2021 21:45:33 -0600 > > > > > > > > > > Bootmethod and bootflow provide a built-in way for U-Boot to > > > > > automatically boot > > > > > an Operating System without custom scripting and other customisation: > > > > > > > > > > - bootmethod - a method to scan a device to find bootflows (owned > > > > > by U-Boot) > > > > > - bootflow - a description of how to boot (owned by the distro) > > > > > > > > > > This series provides an initial implementation of these, enable to > > > > > scan > > > > > for bootflows from MMC and Ethernet. The only bootflow supported is > > > > > distro boot, i.e. an extlinux.conf file included on a filesystem or > > > > > tftp server. 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. > > > > > > > > > > It is intended that this approach be expanded to support mechanisms > > > > > other > > > > > than distro boot, including EFI-related ones. With a standard way to > > > > > identify boot devices, these features become easier. It also should > > > > > support U-Boot scripts, for backwards compatibility only. > > > > > > > > > > The first patch of this series moves boot-related code out of common/ > > > > > and > > > > > into a new boot/ directory. This helps to collect these related files > > > > > in one place, as common/ is quite large. > > > > > > > > > > Like sysboot, this feature makes use of the existing PXE > > > > > implementation. > > > > > Much of this series consists of cleaning up that code and refactoring > > > > > it > > > > > into something closer to a module that can be called, teasing apart > > > > > its > > > > > reliance on the command-line interpreter to access filesystems and the > > > > > like. Also it now uses function arguments and its own context struct > > > > > internally rather than environment variables, which is very hard to > > > > > follow. No core functional change is included in the included PXE > > > > > patches. > > > > > > > > > > For documentation, see the 'doc' patch. > > > > > > > > > > There is quite a long list of future work included in the > > > > > documentation. > > > > > One question is the choice of naming. Since this is a bootloader, > > > > > should > > > > > we just call this a 'method' and a 'flow' ? The 'boot' prefix is > > > > > already > > > > > shared by other commands like bootm, booti, etc. > > > > > > > > > > The design is described here: > > > > > > > > > > https://drive.google.com/file/d/1ggW0KJpUOR__vBkj3l61L2dav4ZkNC12/view?usp=sharing > > > > > > > > > > The series is available at u-boot-dm/bmea-working > > > > > > > > How does the user control the order in which devices are scanned/booted? > > > > > > That is not supported in distroboot at present, at least so far as I > > > can see. For Fedora it seems to happen in grub. Do I have that right? > > > > Well, there's "find the next stage", which is boot_targets environment > > variable, and then "where that next stage looks for stuff" which is > > OS-dependent. Sometimes the ESP grub.cfg file is just enough to tell > > grub to find the full grub.cfg file elsewhere, and sometimes it's a full > > grub.cfg file. I think Mark is talking about the former, and you've > > said it's not part of this series, yet, but on the TODO list. > > Right. With the current distroboot code the order of the devices that > appears in boot_targets is determined by per-board/SOC/machine config > files and the order isn't the same for all of them. Users can change > the order if necessary by modifying the environment variable and > saving the environment. And for a one-off boot from a different > device they can simply run an appropriate boot command. The > boot_targets variable in particular is documented in various install > documents so it would probably be good of the new "bootmethod" code > would respect this variable. > > For OpenBSD I'm not really interested in the bootflow part. As I > explained in the past, that part of the problem is solved in a > (mostly) uniform way across platforms by the OpenBSD bootloader which > can read an /etc/boot.conf that allows bootflow customization. So as > long as the default of the new code still results in > \EFI\BOOT\BOOT{machine type short-name}.EFI being loaded and run if > there is no U-Boot specific bootflow configured, I'm happy. Mostly the same for FreeBSD, as long as the efi boot<arch>.efi is loaded and run by default (respecting the boot_targets order) we will be fine. > I can't speak for the other BSDs, but my impression is that they are > pretty much in the same position. The FreeBSD bootloader for example > supports a high-degree of "bootflow" customization and I doubt that > taking it out of the loop is a viable option for most users. > > > -- > > Tom > > > > [2:application/pgp-signature Show Save:signature.asc (659B)] > > -- Emmanuel Vadot <m...@bidouilliste.com> <m...@freebsd.org>