liburing defined setup flags not supported by the kernel

[aeolio]

liburing uses its own version of io_uring.h, copied from the kernel source tree. Using newer versions of liburing with older kernels, IORING_SETUP_* flags may be defined that the kernel system call (io_uring_setup) rejects returning EINVAL. Since the flags are defined, the usual preprocessor directive cannot be used. Is there a more elegant way than executing io_uring_queue_init() twice? That would result in four system calls altogether, because liburing does something similar with IORING_SETUP_NO_SQARRAY internally ...

Technical information: linux-5.10.235, liburing-2.6, the offending flag is IORING_SETUP_SINGLE_ISSUER, introduced in linux-6.0.

[isilence]

I was thinking about adding an api for probing to the kernel, but nothing nice is currently available.

[aeolio]

Thank you for your assessment; I shall use the workaround for backward compatibility.

[tavianator]

What about #1292?

[aeolio]

@tavianator: I have a few constraints that I have to live with; one is backward compatibility. To add some background: the application using io_uring is MPD, the build environment Buildroot. MPD requires liburing >= 2.5, latest Buildroot ships liburing 2.6. MPD will not accept a pull request requiring a future, not yet released, version of liburing ...