mrc_query_device() / mrc_device_attr version

[sayantansur]

The function mrc_query_device() returns struct mrc_device_attr, but does not take in an mrc_context.

The mrc_context carries the API version information. Without this information, the provider lib doesn't know which version of the output structure the user is expecting.

Should we extend mrc_query_device() to include mrc_context?

@rssohan @insanum.

[insanum]

Hey Sayantan, We never defined the contents of mrc_context. We left that to the vendor. I think we would need add another argument to mrc_query_device() called "mrc_api_version_used" (or similar) where the caller specifies the version it's using. This might require the caller to call mrc_query_version() before mrc_query_device() to ensure a proper version is available. If you agree, we should probably add a "supported" argument to mrc_query_version(). - e

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On Wed, May 13, 2026 at 5:12 AM Sayantan Sur ***@***.***> wrote: *sayantansur* created an issue (opencomputeproject/OCP-Multipath-Reliable-Connection#2) <#2> The function mrc_query_device() returns struct mrc_device_attr, but does not take in an mrc_context. The mrc_context carries the API version information. Without this information, the provider lib doesn't know which version of the output structure the user is expecting. Should we extend mrc_query_device() to include mrc_context? @rssohan <https://github.com/rssohan> @insanum <https://github.com/insanum>. — Reply to this email directly, view it on GitHub <#2>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAD55I3S3ACSFYFNMVQ7SH342RREFAVCNFSM6AAAAACY4MJCTCVHI2DSMVQWIX3LMV43ASLTON2WKOZUGQZTONZUGE2TMOI> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[sayantansur]

The point is that mrc_context contains at least, the version being used by the application (because the context_attr contains the version used). The rest as you say is controlled by the vendor library and is opaque.

Therefore, I was thinking that this would work:

int mrc_query_device(struct ibv_context *context, struct mrc_context *mrc_ctx, struct mrc_device_attr *attr, int *supported);

[sayantansur]

If you agree, we should probably add a "supported" argument to mrc_query_version().

There is a small issue with this. without the ibv_context, we can't really say if MRC is supported.

Another option could be to add a separate call that does not return MRC device attr. Such as,

int mrc_query_support(struct ibv_context *context, int *supported);