MLX5DV_ALLOC_VAR(3)

NAME 💖

okay so this is the manual page for mlx5dv_alloc_var / mlx5dv_free_var(3) — bestie, it's literally two functions: one allocates a VAR, the other frees a VAR. ✨

• mlx5dv_alloc_var — allocates a VAR. 🎀
• mlx5dv_free_var — frees a VAR. 🦋

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SYNOPSIS 🌸

#include <infiniband/mlx5dv.h>

struct mlx5dv_var *
mlx5dv_alloc_var(struct ibv_context *context, uint32_t flags);

void
mlx5dv_free_var(struct mlx5dv_var *dv_var);

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DESCRIPTION 🧚

So you create / free a VAR, and that VAR can be used for some device commands over the DEVX interface. That's the whole vibe. 💅

The DEVX API enables direct access from the user space area to the mlx5 device driver, and the VAR information is needed for few commands related to Virtio. iykyk. 🔥

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ARGUMENTS 🫶

• context — RDMA device context to work on.
• flags — allocation flags for the UAR.

dv_var — the struct involved, and here's exactly how it looks:

struct mlx5dv_var {
    uint32_t page_id;
    uint32_t length;
    off_t mmap_off;
    uint64_t comp_mask;
};

Its members are:

• page_id — the device page id to be used.
• length — the mmap length parameter to be used for mapping a VA to the allocated VAR entry.
• mmap_off — the mmap offset parameter to be used for mapping a VA to the allocated VAR entry.

comp_mask is in the struct too, but the page doesn't give it its own description — not me inventing lore. 🙈

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RETURN VALUE 😭

Upon success, mlx5dv_alloc_var returns a pointer to the created VAR. On error, NULL will be returned and errno will be set. That's the rule, bestie — check that pointer. 🫶

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SEE ALSO 🌈

• mlx5dv_open_device
• mlx5dv_devx_obj_create

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AUTHOR 👑

Yishai Hadas <yishaih@mellanox.com>

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That's the page, bestie! The original footer doesn't list a source, version, or date — no extra tea there — so this cute sign-off is just me confirming there's no source/version/date info in the footer to report. 💖🎀✨