Re: [PATCH v2 00/41] Initial implementation of standard boot

From: Simon Glass <sjg@chromium.org>
To: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Cc: "Michal Simek" <michal.simek@xilinx.com>,
	"Tom Rini" <trini@konsulko.com>,
	"Ilias Apalodimas" <ilias.apalodimas@linaro.org>,
	"Daniel Schwierzeck" <daniel.schwierzeck@gmail.com>,
	"Steffen Jaeckel" <jaeckel-floss@eyet-services.de>,
	"Marek Behún" <marek.behun@nic.cz>,
	"Lukas Auer" <lukas.auer@aisec.fraunhofer.de>,
	"Dennis Gilmore" <dennis@ausil.us>,
	"Jaehoon Chung" <jh80.chung@samsung.com>,
	"Marek Vasut" <marex@denx.de>,
	"Masahiro Yamada" <yamada.masahiro@socionext.com>,
	"Pavel Herrmann" <morpheus.ibis@gmail.com>,
	"Peng Fan" <peng.fan@nxp.com>,
	"Stephen Warren" <swarren@nvidia.com>,
	"Stephen Warren" <swarren@wwwdotorg.org>,
	"François Ozog" <francois.ozog@linaro.org>,
	"Heinrich Schuchardt" <xypron.glpk@gmx.de>,
	"U-Boot Mailing List" <u-boot@lists.denx.de>
Subject: Re: [PATCH v2 00/41] Initial implementation of standard boot
Date: Wed, 27 Oct 2021 08:11:03 -0600	[thread overview]
Message-ID: <CAPnjgZ1X=W-oahudMXBC+UAQ3ogOFP32TgkVTSpemCS2kqnqBg@mail.gmail.com> (raw)
In-Reply-To: <3fde4b98-e7c0-71c3-d7c4-22c6f43eae31@canonical.com>

Hi Heinrich,

On Wed, 27 Oct 2021 at 05:38, Heinrich Schuchardt
<heinrich.schuchardt@canonical.com> wrote:
>
>
>
> On 10/24/21 01:25, 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)
>
> Please, describe why you are suggesting this change.
>
> Replacing a script by a devicetree chunk is just decreasing flexibility
> and increasing complexity. Where is the benefit?
>
> I am missing a description here of where and how a boot flow shall be
> defined. Describing some device-tree binding in patch 40/41 does not
> replace describing the development and usage workflow. Who will provide
> which bootflow information when?
>
> You still have an open discussion with Linaro about the source of
> devicetrees. This discussion needs to be finalized before considering
> this series.
>
> In my view bootflows cannot be defined in the devicetree because prior
> firmware providing a devicetree is completely independent of any distro
> and therefore cannot provide a distro specific bootflow.

There is actually no need to use devicetree here. I think you might
have the wrong end of the stick. It is certainly possible to add nodes
to configure things, if needed, but it works find without any changes
to the devicetree, as you can see from the rpi_3 patch.

There are several aims with this effort:

- Provide a standard way to boot anything on U-Boot, that everyone can
plug into (distros, board vendors, people using a custom flow)
- Move all this stuff out of the environment so we can move to a
text-based environment that doesn't rely on ad-hoc CONFIG options
   (this unblocks the 7-year-old CONFIG migration)
- Add proper tests to cover this important functionality (the scripts
have no tests)
   (this makes development much easier and faster)
- Provide a path to booting more 'directly' without needing the CLI
(which adds size / security risk)

This initial series is not the end of the matter. I expect various
other people will contribute to cover their use cases and additional
features, but at least now we have good basis for this development and
innovation.

[..]

Regards,
Simon