libnvme(2)

💖 struct nvme_mi_admin_req_hdr — the admin command request header 💖

okay bestie, so this is a page from the libnvme(2) API manual, and today's main character is struct nvme_mi_admin_req_hdr, which is literally the admin command request header. that's it, that's the vibe. it's giving wire format. it's giving struct energy. let's get into it 🫶

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✨ NAME ✨

struct nvme_mi_admin_req_hdr — Admin command request header. no cap, that's what it is. 👑

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🌸 SYNOPSIS 🌸

struct nvme_mi_admin_req_hdr {
    struct nvme_mi_msg_hdr hdr;
    __u8 opcode;
    __u8 flags;
    __le16 ctrl_id;
    __le32 cdw1, cdw2, cdw3, cdw4, cdw5;
    __le32 doff;
    __le32 dlen;
    __le32 rsvd0, rsvd1;
    __le32 cdw10, cdw11, cdw12, cdw13, cdw14, cdw15;
 };

like look at her. every field exactly where it's supposed to be. immaculate layout. no notes. 💅

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🦋 Members 🦋

okay so let's go field by field because every single one of these is doing something, and we do NOT skip fields in this house.

• hdr — Generic MI message header. the little base she stands on, iconic, foundational, main character origin story. ✨
• opcode — Admin command opcode (using enum nvme_admin_opcode). this is the "which admin command are we even doing" field.
• flags — Command Flags, indicating dlen and doff validity; Only defined in NVMe-MI version 1.1, no fields defined in 1.2 (where the dlen/doff are always considered valid). so like, version-dependent behaviour, we love a conditional queen.
• ctrl_id — Controller ID target of command. who is this command for? her. exactly. 💖
• cdw1 — Submission Queue Entry doubleword 1
• cdw2 — Submission Queue Entry doubleword 2
• cdw3 — Submission Queue Entry doubleword 3
• cdw4 — Submission Queue Entry doubleword 4
• cdw5 — Submission Queue Entry doubleword 5
• doff — Offset of data to return from command. where in the data do we start? there, bestie. 🎀
• dlen — Length of sent/returned data. how much data are we sending or getting back? this many.
• rsvd0 — Reserved. don't touch. do not perceive her. 🙈
• rsvd1 — Reserved. also don't touch. also do not perceive. 🌸
• cdw10 — Submission Queue Entry doubleword 10
• cdw11 — Submission Queue Entry doubleword 11
• cdw12 — Submission Queue Entry doubleword 12
• cdw13 — Submission Queue Entry doubleword 13
• cdw14 — Submission Queue Entry doubleword 14
• cdw15 — Submission Queue Entry doubleword 15

note bestie: yes, the doublewords jump from cdw5 straight to cdw10, and yeah the reserved fields are just vibing in between. that's not a typo, that's just how the struct is built. periodt. 💀

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🌈 Description 🌈

Wire format for Admin command message headers, defined in section 6 of NVMe-MI. that's the whole thing. she's a wire format. she shows up on the wire. section 6 said so. iykyk. ⭐

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and that's the page bestie, we ate, no crumbs left 💅

signing off from the libnvme(2) manual, dated July 2026 — this was struct nvme_mi_admin_req_hdr, brought to you by libnvme, and she slayed. 🎀✨