Re: [OE-core] [PATCH v2] u-boot-tools: Add dependency on libyaml for dtschema validation

[Quentin Schulz <quentin.schulz@cherry.de>]

Hi Khem,

On 4/12/26 5:57 AM, Khem Raj via lists.openembedded.org wrote:
> yamltree host tool, used to emit YAML from the DT, is now
> built as part of the normal u-boot-tools build to support
> the schema infrastructure
> 
> Fixes link errors like
> 
> | /usr/bin/ld: scripts/dtc/yamltree.o: in function `dt_to_yaml':
> | yamltree.c:(.text+0x91b): undefined reference to `yaml_emitter_initialize'
> | /usr/bin/ld: yamltree.c:(.text+0x926): undefined reference to `yaml_emitter_set_output_file'
> | /usr/bin/ld: yamltree.c:(.text+0x933): undefined reference to `yaml_stream_start_event_initialize'
> | /usr/bin/ld: yamltree.c:(.text+0x93e): undefined reference to `yaml_emitter_emit'
> | /usr/bin/ld: yamltree.c:(.text+0x957): undefined reference to `yaml_document_start_event_initialize'
> | /usr/bin/ld: yamltree.c:(.text+0x962): undefined reference to `yaml_emitter_emit'
> | /usr/bin/ld: yamltree.c:(.text+0x983): undefined reference to `yaml_sequence_start_event_initialize'
> | /usr/bin/ld: yamltree.c:(.text+0x98e): undefined reference to `yaml_emitter_emit'
> | /usr/bin/ld: yamltree.c:(.text+0x9ab): undefined reference to `yaml_sequence_end_event_initialize'
> | /usr/bin/ld: yamltree.c:(.text+0x9b6): undefined reference to `yaml_emitter_emit'
> | /usr/bin/ld: yamltree.c:(.text+0x9c8): undefined reference to `yaml_document_end_event_initialize'
> | /usr/bin/ld: yamltree.c:(.text+0x9d3): undefined reference to `yaml_emitter_emit'
> | /usr/bin/ld: yamltree.c:(.text+0x9e3): undefined reference to `yaml_stream_end_event_initialize'
> | /usr/bin/ld: yamltree.c:(.text+0x9ee): undefined reference to `yaml_emitter_emit'
> | /usr/bin/ld: yamltree.c:(.text+0x9fa): undefined reference to `yaml_emitter_delete'
> 

OK so there's a test to check if libyaml is available by looking if 
there's a file at $(PKG_CONFIG_SYSROOT_DIR)/usr/include/yaml.h. Then it 
uses pkg-config --cflags and pkg-config --libs on yaml-0.1 to find where 
that is located. I'm assuming the first one is found, possibly on the 
host distro, and the pkg-config possibly returns nothing as libyaml 
isn't available in the sysroot? This seems to be what 807bcd844afe 
("scripts/dtc: Fix pkg-config behavior under sysroot") is supposed to 
handle (specifically mentioning this fixes building with Yocto SDK). 
This commit is part of 2026.04, so not sure what's going on there. They 
say the error doesn't happen within Yocto because pseudo intercepts and 
rewrites the path, so this seems weird.

This logic is also borrowed from the kernel, which funnily enough 
dropped this entirely 4 years ago, in commit ef8795f3f1ce ("dt-bindings: 
kbuild: Use DTB files for validation"). So maybe something to work on 
with U-Boot to update DTC again (Kbuild and DTC updates aren't trivial 
in U-Boot as far as I understood as we have "lightly" forked it).

Cheers,
Quentin