mlx5dv_create_cq(3)

✨ mlx5dv_create_cq — it's giving completion queue energy ✨

okay so bestie, this one's from the mlx5 Programmer's Manual, and it's lowkey iconic. sit down, grab a boba, we're making a completion queue 🎀

💖 NAME 💖

mlx5dv_create_cq — creates a completion queue (CQ). that's it. that's the vibe. 🦋

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🌸 SYNOPSIS 🌸

#include <infiniband/mlx5dv.h>

struct ibv_cq_ex *mlx5dv_create_cq(struct ibv_context *context,
                                   struct ibv_cq_init_attr_ex *cq_attr,
                                   struct mlx5dv_cq_init_attr *mlx5_cq_attr);

three args, one CQ, no cap 💅

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✨ DESCRIPTION ✨

mlx5dv_create_cq() creates a completion queue (CQ) — but like, with specific driver properties. not your basic CQ, a customized CQ. main character behavior honestly 👑

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🫶 ARGUMENTS 🫶

so for context and cq_attr, please see the ibv_create_cq_ex(3) man page, mwah 💋

🧚 mlx5_cq_attr 🧚

here's the struct, look at her:

struct mlx5dv_cq_init_attr {
    uint64_t comp_mask;
    uint8_t  cqe_comp_res_format;
    uint32_t flags;
    uint16_t cqe_size;
};

comp_mask

it's a bitmask specifying which fields in the struct are actually valid (like a vibe check for your struct 👀):

• MLX5DV_CQ_INIT_ATTR_MASK_COMPRESSED_CQE — enables creating a CQ in a mode where, like, a few CQEs may be compressed into a single CQE. valid values live in cqe_comp_res_format (see below, bestie ⬇️)
• MLX5DV_CQ_INIT_ATTR_MASK_FLAGS — valid values live in flags
• MLX5DV_CQ_INIT_ATTR_MASK_CQE_SIZE — valid values live in cqe_size

cqe_comp_res_format

a bitwise OR of the various CQE response formats of the responder side (yes, you can stack them, we love a bitwise OR 🔥):

• MLX5DV_CQE_RES_FORMAT_HASH — CQE compression with hash
• MLX5DV_CQE_RES_FORMAT_CSUM — CQE compression with RX checksum
• MLX5DV_CQE_RES_FORMAT_CSUM_STRIDX — CQE compression with stride index

flags

a bitwise OR of the various values described below:

• MLX5DV_CQ_INIT_ATTR_FLAGS_CQE_PAD — create a padded 128B CQE

cqe_size

configure the CQE size to be 64 or 128 bytes. and like — other values will fail mlx5dv_create_cq. no in-between, no "but what if I want 96", just no 💀 the function said what it said.

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🌈 RETURN VALUE 🌈

mlx5dv_create_cq() returns a pointer to the created CQ — slay 🎉 — or NULL if the request fails, and errno will be set. (so check your returns, bestie, don't just vibe and hope 😭)

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👀 SEE ALSO 👀

• ibv_create_cq_ex(3)

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💜 AUTHOR 💜

Yonatan Cohen <yonatanc@mellanox.com> — thank you for your service 🫡

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and that's the whole page, periodt 💅 this icon dropped in mlx5, dated 2018-9-1 — a classic, honestly. go forth and make your CQs, bestie, you got this 💖✨🎀