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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | COLOPHON |
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io_uring_register_query(3) liburing Manual io_uring_register_query(3)
io_uring_register_query - query io_uring capabilities and feature
support
#include <liburing.h>
int io_uring_register_query(struct io_uring_query_hdr *query);
The io_uring_register_query(3) function queries io_uring
capabilities and feature support. It provides information about
supported opcodes, flags, and subsystem-specific capabilities.
The query argument must point to a struct io_uring_query_hdr
structure that describes the query to perform:
struct io_uring_query_hdr {
__u64 next_entry;
__u64 query_data;
__u32 query_op;
__u32 size;
__s32 result;
__u32 __resv[3];
};
The next_entry field can be used to chain multiple queries
together. It should point to the next struct io_uring_query_hdr
structure, or be set to 0 for the last entry in the chain.
The query_data field must point to a data structure appropriate
for the query type specified in query_op.
The query_op field specifies the type of query to perform and can
be one of:
IO_URING_QUERY_OPCODES
Returns information about supported opcodes and flags. The
query_data field must point to a struct
io_uring_query_opcode structure, which will be filled with
information about supported request opcodes, register
opcodes, feature flags, setup flags, enter flags, and SQE
flags.
IO_URING_QUERY_ZCRX
Returns information about zero-copy receive support. The
query_data field must point to a struct io_uring_query_zcrx
structure, which will be filled with information about
supported zero-copy receive flags, features, and
configuration details.
IO_URING_QUERY_SCQ
Returns information about the SQ/CQ ring layout. The
query_data field must point to a struct io_uring_query_scq
structure, which will be filled with information about ring
header size and alignment requirements.
The size field should be set to the size of the data structure
pointed to by query_data.
Upon return, the result field will contain 0 on success, or a
negative error code on failure.
The reserved __resv fields must be cleared to zero.
Returns 0 on success. On error, a negative errno value is
returned.
This function is available since Linux kernel 6.15.
Multiple queries can be efficiently performed in a single system
call by chaining them together using the next_entry field.
io_uring_register(2), io_uring_setup(2)
This page is part of the liburing (A library for io_uring)
project. Information about the project can be found at
⟨https://github.com/axboe/liburing⟩. If you have a bug report for
this manual page, send it to io-uring@vger.kernel.org. This page
was obtained from the project's upstream Git repository
⟨https://github.com/axboe/liburing⟩ on 2026-08-04. (At that time,
the date of the most recent commit that was found in the
repository was 2026-07-28.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
liburing-2.15 March 26, 2026 io_uring_register_query(3)
Pages that refer to this page: io_uring_register_query(3)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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