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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | COLOPHON |
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io_uring_register_buf_ring(3)liburing Manualo_uring_register_buf_ring(3)
io_uring_register_buf_ring - register buffer ring for provided
buffers
#include <liburing.h>
int io_uring_register_buf_ring(struct io_uring *ring,
struct io_uring_buf_reg *reg,
unsigned int flags);
The io_uring_register_buf_ring(3) function registers a shared
buffer ring to be used with provided buffers. For the request
types that support it, provided buffers are given to the ring and
one is selected by a request if it has IOSQE_BUFFER_SELECT set in
the SQE flags, when the request is ready to receive data. This
allows both clear ownership of the buffer lifetime, and a way to
have more read/receive type of operations in flight than buffers
available.
The reg argument must be filled in with the appropriate
information. It looks as follows:
struct io_uring_buf_reg {
__u64 ring_addr;
__u32 ring_entries;
__u16 bgid;
__u16 pad;
__u64 resv[3];
};
The ring_addr field must contain the address to the memory
allocated to fit this ring. The memory must be page aligned and
hence allocated appropriately using eg posix_memalign(3) or
similar. The size of the ring is the product of ring_entries and
the size of struct io_uring_buf. ring_entries is the desired
size of the ring, and must be a power-of-2 in size. The maximum
size allowed is 2^15 (32768). bgid is the buffer group ID
associated with this ring. SQEs that select a buffer have a
buffer group associated with them in their buf_group field, and
the associated CQEs will have IORING_CQE_F_BUFFER set in their
flags member, which will also contain the specific ID of the
buffer selected. The rest of the fields are reserved and must be
cleared to zero.
The flags argument is currently unused and must be set to zero.
A shared buffer ring looks as follows:
struct io_uring_buf_ring {
union {
struct {
__u64 resv1;
__u32 resv2;
__u16 resv3;
__u16 tail;
};
struct io_uring_buf bufs[0];
};
};
where tail is the index at which the application can insert new
buffers for consumption by requests, and struct io_uring_buf is
buffer definition:
struct io_uring_buf {
__u64 addr;
__u32 len;
__u16 bid;
__u16 resv;
};
where addr is the address for the buffer, len is the length of
the buffer in bytes, and bid is the buffer ID that will be
returned in the CQE once consumed.
Reserved fields must not be touched. Applications must use
io_uring_buf_ring_init(3) to initialise the buffer ring.
Applications may use io_uring_buf_ring_add(3) and
io_uring_buf_ring_advance(3) or io_uring_buf_ring_advance(3) to
provide buffers, which will set these fields and update the tail.
Available since 5.19.
On success io_uring_register_buf_ring(3) returns 0. On failure it
returns -errno.
io_uring_buf_ring_init(3), io_uring_buf_ring_add(3),
io_uring_buf_ring_advance(3), io_uring_buf_ring_cq_advance(3)
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 2022-12-17. (At that
time, the date of the most recent commit that was found in the
repository was 2022-12-12.) 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-2.2 May 18, 2022 io_uring_register_buf_ring(3)
Pages that refer to this page: io_uring_register(2), io_uring_buf_ring_add(3), io_uring_buf_ring_advance(3), io_uring_buf_ring_cq_advance(3), io_uring_buf_ring_init(3), io_uring_buf_ring_mask(3), io_uring_register_buffers(3), io_uring_register_buf_ring(3), io_uring_register_file_alloc_range(3), io_uring_sqe_set_flags(3), io_uring_unregister_buf_ring(3)
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