Re: [PATCH v5 5/5] fastboot: add SPL support

[Mattijs Korpershoek <mkorpershoek@kernel.org>]

Hi Carlo,

Thank you for the patch.

On Sun, Sep 06, 2026 at 22:02, Carlo Caione <ccaione@baylibre.com> wrote:

> Some recovery and initial-provisioning flows run before usable firmware
> is available in persistent storage. In these flows the SoC ROM loads a
> small first stage, but that stage must still provide a standard protocol
> with which the host can provision the device.
>
> U-Boot already provides fastboot for this purpose, but its implementation
> is currently restricted to U-Boot proper and coupled to command-line
> support. This forces platforms that need provisioning from SPL to maintain
> a separate downloader or an out-of-tree fastboot implementation.
>
> Allow boards to run USB fastboot as a service directly from SPL. Include
> MMC partition flashing and Android sparse-image handling so that the SPL
> service can provision the same storage images accepted by fastboot in
> U-Boot proper.
>
> Keep the SPL interface deliberately narrower. The fastboot boot command
> is not supported because SPL is being used for provisioning rather than
> OS boot orchestration. Filesystem probing is also omitted, so partition
> types are reported as raw. Reboot support remains optional since reset
> and persistent reboot-reason handling are platform-specific.
>
> Environment-backed USB serial numbers, getvars, MMC aliases and raw
> partition descriptors are available when SPL_ENV_SUPPORT is enabled, but
> the core service no longer requires the environment. Document the full
> printf, allocator, reset, command and shared-buffer requirements.
>
> SPL size remains an important constraint. Make the support entirely
> opt-in and phase-specific: when CONFIG_SPL_FASTBOOT is disabled, no
> fastboot code or supporting library is added to SPL. Enable the core
> service in sandbox_spl so this build path receives CI compile coverage.
>
> Signed-off-by: Julien Masson <jmasson@baylibre.com>
> Signed-off-by: Vitor Sato Eschholz <vsatoes@baylibre.com>
> Signed-off-by: Carlo Caione <ccaione@baylibre.com>

Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>

> ---