libnvme(2)

💖 libnvme(2) — the manual page, but make it a group chat 💖

okay bestie, sit down, we're reading a page out of the libnvme API manual and honestly? it's giving internal-state gossip. it's struct nvme_telemetry_log. no cap, it's important. let's go 🌸

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✨ NAME ✨

struct nvme_telemetry_log — Retrieve internal data specific to the manufacturer. 👀

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🎀 SYNOPSIS 🎀

struct nvme_telemetry_log {
    __u8 lpi;
    __u8 rsvd1[4];
    __u8 ieee[3];
    __le16 dalb1;
    __le16 dalb2;
    __le16 dalb3;
    __u8 rsvd14[2];
    __le32 dalb4;
    __u8 rsvd20[360];
    __u8 ths;
    union {
      __u8 hostdgn;
      __u8 tcs;
    };
    __u8 ctrlavail;
    __u8 ctrldgn;
    __u8 rsnident[128];
    __u8 data_area[];
};

not me just typing out every single field exactly as it is, because that's the whole vibe 💅

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👑 Members 👑

here's the full roster, main character by main character:

• lpi — the Log Identifier, and it's either NVME_LOG_LID_TELEMETRY_HOST or NVME_LOG_LID_TELEMETRY_CTRL. pick your fighter ✨
• rsvd1 — Reserved. no thoughts, just vibes, don't touch it 🫶
• ieee — the IEEE OUI Identifier, aka the Organization Unique Identifier (OUI) for whichever controller vendor is out here being able to interpret the data. it's literally their name tag 💳
• dalb1 — Telemetry Host/Controller Initiated Data Area 1 Last Block, and it's the value of the last block in this area. so it's the last-block bouncer of Area 1 🚪
• dalb2 — Telemetry Host/Controller Initiated Data Area 1 Last Block is the value of the last block in this area. (yes the wording says "Data Area 1" for this one too, i'm just the messenger 💀)
• dalb3 — Telemetry Host/ControllerInitiated Data Area 1 Last Block is the value of the last block in this area. same wording situation, and also the same, and also note it says ControllerInitiated with no space. character for character, bestie 🤝
• rsvd14 — Reserved. still reserved. still not for us 🙈
• dalb4 — Telemetry Host/Controller Initiated Data Area 4 Last Block is the value of the last block in this area. and yes, this one says Area 4 🌈
• rsvd20 — Reserved. that's it, that's the description 😌
• ths — Telemetry Host-Initiated Scope 🔭
• {unnamed_union} — anonymous. it's an unnamed union, it has no name, it's mysterious, it's the cool quiet one 🦋
  • hostdgn — Telemetry Host-Initiated Data Generation Number, which is a value that gets incremented each and every time the host initiates a capture of its internal controller state in the controller. counter goes brrr ⬆️
  • tcs — Telemetry Controller-Initiated Scope 🔭
• ctrlavail — Telemetry Controller-Initiated Data Available. if it's cleared, then the controller telemetry log does not contain saved internal controller state. if this field is set to 1h, the controller log contains saved internal controller state. and if this field is set to 1h, the data will be latched until the host releases it by reading the log with RAE cleared. big latch energy 🫣
• ctrldgn — Telemetry Controller-Initiated Data Generation Number, a value that is incremented each time the controller initiates a capture of its internal controller state in the controller . (yes there's a space before that period. iconic behavior. keeping it. periodt.) 😭
• rsnident — Reason Identifiers, a vendor specific identifier that describes the operating conditions of the controller at the time of capture. it's the "how were you feeling when this happened" field 🍓
• data_area — Telemetry data blocks, vendor specific information data. the payload. the moment. the finale 🌟

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💫 Description 💫

so THIS log? it consists of a header that describes the log, plus zero or more Telemetry Data Blocks. and every single Telemetry Data Block is NVME_LOG_TELEM_BLOCK_SIZE, which is 512 bytes, in size — exact number, don't round it, don't guess it 💅

and what does the whole thing do? it captures the controller's internal state. that's the entire plot. it's a little diary of what the controller was going through 📓✨

lowkey a glow-up of a struct. highkey useful. but pls pls pls respect the reserved fields — they said reserved and they meant it 🚫

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that's the whole page, bestie, you ate it 🫶

this was struct nvme_telemetry_log from the 🌈 libnvme(2) 🌈 API manual, dated July 2026. go forth and log your telemetry, queen 👑💖