[PATCH 3/3] efi_loader: disk: add EFI_PARTITION_INFO_PROTOCOL support

[Tom Rini]

On Fri, Jun 13, 2025 at 04:54:48PM +0200, Javier Martinez Canillas wrote:
> Heinrich Schuchardt <xypron.glpk at gmx.de> writes:
> 
> Hello Heinrich,
> 
> Thanks for your feedback.
> 
> > Am 13. Juni 2025 10:57:38 MESZ schrieb Javier Martinez Canillas <javierm at redhat.com>:
> >>The UEFI 2.10 specification mentions that this protocol shall be installed
> >>along with EFI_BLOCK_IO_PROTOCOL. It provides cached partition information
> >>for MBR and GPT partition types.
> >
> > U-Boot is targeting the EBBR specifcation which defines a subset of UEFI.
> >
> 
> Interesting. I knew that the u-boot EFI implementation was to support
> SystemReady IR (what is now called SystemReady DeviceTree) and EBBR,
> but I didn't know that meant to only implement what's required by EBBR.
> 
> I noticed that EFI_PARTITION_INFO_PROTOCOL is not even required by SBBR
> and only EFI_BLOCK_IO_PROTOCOL is required there just like for EBBR.
> 
> > Which application needs this protocol?
> 
> We are experimenting with a new A/B boot protocol and an EFI binary that
> implements it. It's inspired on what the Android Boot Loader does for its
> A/B booting too.
> 
> The project is https://gitlab.com/CentOS/automotive/src/ukiboot and reads
> UKI (https://uapi-group.org/specifications/specs/unified_kernel_image)
> images from raw data partitions. Just like ABL reads Android Boot images.
> 
> > Are you planning to add it to the EBBR specification?
> >
> 
> I haven't thought about it before but I also didn't know that u-boot had
> this requirement. Probably it should be documented somewhere to make it
> more clear? Maybe I didn't look enough but didn't find a doc in the repo.

We are not strictly and only EBBR requirements, if there is good reason
to add more features (and tests). But Heinrich's follow-up question is
quite important. I feel like there's already a half dozen offerings of
A/B update that works within UEFI.

-- 
Tom
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