[PATCH v3 0/2] bootstd: New bootmeth for RAUC A/B systems

[Martin Schwan]

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Hi Simon,

On Thu, 2025-06-05 at 11:29 -0600, Simon Glass wrote:
> Hi Martin,
> 
> On Wed, 4 Jun 2025 at 06:16, Martin Schwan <m.schwan at phytec.de>
> wrote:
> > 
> > This series implements a new bootmeth for RAUC A/B systems. RAUC
> > (Robust
> > Auto Update Controller) is a lightweight update client, providing
> > "Safe
> > and Secure OTA Updates for Embedded Linux". See the following links
> > for
> > more information about RAUC:
> > 
> >   https://rauc.io/
> >   https://rauc.readthedocs.io/en/latest/
> > 
> > PHYTEC uses RAUC in its Yocto based distribution "Ampliphy" as the
> > default way of updating embedded devices based on PHYTEC hardware.
> > So
> > far, the logic selecting the correct partitions and files to boot
> > was
> > being implemented in the U-Boot environment. While this is a
> > straightforward way to do it, adding and supporting new platforms
> > became
> > somewhat tedious and is platform-specific. The introduction of U-
> > Boot's
> > "Standard Boot" provided a convincing alternative, promising a
> > simpler
> > and more portable way of booting, even for RAUC systems. This led
> > me to
> > implement a new bootmeth supporting RAUC A/B systems. Note, that
> > this
> > new bootmeth is not proprietary to PHYTEC products and is designed
> > to
> > work on other hardware with a RAUC A/B system, too.
> > 
> > The bootmeth currently only supports symmetric A/B partitioning
> > layouts.
> > E.g. A/rescue is not (yet) supported. The partition indexes and
> > default
> > slot tries can be specified via configuration options.
> > 
> > For now, the bootmeth_rauc uses a similar approach for loading the
> > Kernel and device tree as the bootmeth_script, in that it requires
> > a FIT
> > containing a U-Boot script loading the desired distro. It could be
> > possible to support booting without a script and load the Kernel
> > and DT
> > directly with this bootmeth, but I found the script method to be
> > very
> > flexible for now, in letting the distro decide what to load.
> > 
> > The bootmeth_rauc was tested on a phyBOARD-Pollux i.MX8M Plus [1]
> > with
> > BSP-Yocto-Ampliphy-i.MX8MP-PD24.1.2 [2].
> > 
> > Supported boot devices are currently only MMC devices, but it
> > should be
> > possible to add SPI flashes in the future.
> > 
> > To test this patch stack with PHYTEC's phyBOARD-Pollux i.MX8M Plus
> > board, you need to adjust the boot files to include the
> > boot.scr.uimg
> > containing the distro's boot script and set "optargs" to
> > "${raucargs}"
> > in it. Also disable any legacyboot in the U-Boot environment and
> > simply
> > boot with Standard Boot:
> > 
> >   bootmeth order rauc
> >   bootflow scan -lb
> > 
> > Regards,
> > Martin
> > 
> > [1]:
> > https://www.phytec.eu/en/produkte/single-board-computer/phyboard-pollux/
> > [2]:
> > https://download.phytec.de/Software/Linux/BSP-Yocto-i.MX8MP/BSP-Yocto-Ampliphy-i.MX8MP-PD24.1.2/
> > 
> > ---
> > Changes in v3:
> > - Invert if-statement check for setting default value of
> > BOOT_*_LEFT env
> >   variables. This would falsely trigger an error message before.
> > - Link to v2:
> > https://lore.kernel.org/r/20250602-wip-bootmeth-rauc-v2-0-9d2384131486@phytec.de
> > 
> > Changes in v2:
> > - Remove LOG_DEBUG from boot/bootmeth_rauc.c
> > - Reorder asm/cache.h include to be last
> > - Do not check for RAUC-specific files in the rootfs anymore. This
> > does
> >   not work on encrypted root filesystems and is not a stable
> > indicator
> >   for a functioning RAUC system.
> > - Add a description of the term "slot" in the corresponding private
> >   struct.
> > - Remove boot tries left from struct distro_rauc_slot. The boot
> > tries
> >   are read directly from the environment, as that's the only
> > correct
> >   source RAUC is relying on.
> > - Remove the current boot_order from struct distro_rauc_priv, for
> > the
> >   same reason as above (env is correct source).
> > - Add function for retrieving a slot struct, to ease finding the
> > right
> >   one when e.g. iterating or getting by name.
> > - Fix multiline comments.
> > - Fix various if-statements which were explicitly comparing to 0 or
> >   NULL.
> > - Free various, temporary instances of allocated string lists.
> > - Set default env values for BOOT_ORDER and associated BOOT_*_LEFT
> >   variables. These variables are mandatory for RAUC to work.
> > - Use calloc() instead of malloc() for allocating the private
> > slots.
> > - Use config options for configuring the partitions and default
> > boot
> >   order, instead of setting them via the U-Boot env.
> > - Use bootstd_get_prefixes()'s return value and check all available
> >   prefixes for the boot script.
> > - Add a proper boot order selection logic for the rauc bootmeth,
> > similar
> >   to the previous environment scripting, with fallbacks and slot
> > try
> >   checks.
> > - Introduce config option for resetting all slot tries in case they
> > are
> >   all zero. This may prevent a system from locking up in the
> > bootloader.
> > - Rename env variable "mmcroot" to "distro_rootpart", to be in line
> > with
> >   "distro_bootpart".
> > - Change the bootmeth flag to "global", as the rauc bootmeth does
> > not
> >   work for individual partitions.
> > - Update documentation accordingly.
> > - Link to v1:
> > https://lore.kernel.org/r/20250129-wip-bootmeth-rauc-v1-0-6308e732f314@phytec.de
> > 
> > ---
> > Martin Schwan (2):
> >       bootstd: Add implementation for bootmeth rauc
> >       doc: Add description for bootmeth rauc
> > 
> >  boot/Kconfig                     |  51 +++++
> >  boot/Makefile                    |   1 +
> >  boot/bootmeth_rauc.c             | 432
> > +++++++++++++++++++++++++++++++++++++++
> >  doc/develop/bootstd/index.rst    |   1 +
> >  doc/develop/bootstd/overview.rst |   1 +
> >  doc/develop/bootstd/rauc.rst     |  56 +++++
> >  6 files changed, 542 insertions(+)
> > ---
> > base-commit: b22a276f039f818d5564bec6637071cfc8a7e432
> > change-id: 20250129-wip-bootmeth-rauc-03b5e2dd88f4
> > 
> > Best regards,
> > --
> > Martin Schwan <m.schwan at phytec.de>
> > 
> 
> Great to see this. Could you please add a test, e.g. to
> test/boot/bootflow.c ? Let me know if you need help.

Thank you! :)

I will have a look into adding a test for it. Sorry, that I didn't make
it for the first iteration, as you mentioned it previously. Will it be
okay, if I add this in a separate patch?

I'll probably not have time for this until end of June, as I'm on
vacation the next two weeks. But I definitely have it on my agenda.

Regards,
Martin

> 
> Regards,
> Simon

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