Implementation Guidance for FIPS 140-3 and the Cryptographic Module Validation Program:
https://csrc.nist.gov/CSRC/media/Projects/cryptographic-module-validation-program/documents/fips%20140-3/FIPS%20140-3%20IG.pdf

Some ideas:

• the someflags thing will probably just be a reserved parameter
• If DATA is not NULL but an MD is set the sign function should fail
• Should ownership of MD be moved to the CTX?

In an email from @werner couple days back, I got a suggestion that we could use hashing tied to the context, rather than this one-shot call tied only to digests. I circled back this suggestion to Stephan and he confirmed that it should be fine from the FIPS point of view so I am posting the suggested API here too:

ctx = gcry_pk_new (someflags)
md = gcry_md_open (...)
gcry_ctx_set_md (md);
gcry_pk_sign_ext (ctx, result, data, skey)
[...]
gcry_ctx_release (ctx);

OK. I think that the patch at SUSE is updated one which works.
As I understand correctly, this is a kind of very old patch, which intended to work around old libgcrypt limitation of RSA PSS.

I think that {D1476} is still a sketch (not real code which works). I would guess an intended use, but it's good to have concrete example program which uses the feature being added.

FWIW, there is also this newer patch: https://dev.gnupg.org/differential/diff/1476/
and SUSE seems to already use a modified API:
https://sources.suse.com/SUSE:Maintenance:15118/libgcrypt.SUSE_SLE-15_Update/26a8df5f96d27d6abca7bd7ba9b0def0/libgcrypt-FIPS-RSA-DSA-ECDSA-hashing-operation.patch

Our public key functions are stateless. For several reasons it would be good to have an option to keep some state (think pre-computations). Our gcry_ctx_t would be a perfect fit for this and it will allow us to join a pubkey function with for example a hash function.

Does the patch really work, or is it a sketch to describe the intended use?

I recall that I talked with Stephan about it but things got lost.