STRUCT EFX_MCDI_IFACE(9)

💅 struct efx_mcdi_iface(9) — like, the whole MCDI protocol context, bestie

okay so this is a page straight out of the Kernel API Manual, and it's all about struct efx_mcdi_iface, aka the MCDI protocol context. no cap, it's giving "the little control room where all the MCDI traffic gets its life together" 🎀

✨ NAME ✨

struct efx_mcdi_iface — MCDI protocol context 🦋

🌸 SYNOPSIS 🌸

struct efx_mcdi_iface {
    struct efx_nic *efx;
    enum efx_mcdi_state state;
    enum efx_mcdi_mode mode;
    wait_queue_head_t wq;
    spinlock_t iface_lock;
    bool new_epoch;
    unsigned int credits;
    unsigned int seqno;
    int resprc;
    int resprc_raw;
    size_t resp_hdr_len;
    size_t resp_data_len;
    spinlock_t async_lock;
    struct list_head async_list;
    struct timer_list async_timer;
  #ifdef CONFIG_SFC_SIENA_MCDI_LOGGING;
    char *logging_buffer;
    bool logging_enabled;
  #endif;
    unsigned int proxy_rx_handle;
    int proxy_rx_status;
    wait_queue_head_t proxy_rx_wq;
 };

like, yes, that's the whole struct, character for character, we do not skip members in this group chat 💖

🧚 Members 🧚

• efx — the NIC this whole thing is attached to, its lil bestie 🫶
• state — the request handling state. wq waits on this one, so it's kind of the main character here ✨
• mode — decides the vibe: poll for an mcdi completion, or wait for an mcdi_event 👑
• wq — the wait queue for threads that are sitting around waiting for state != MCDI_STATE_RUNNING 😭
• iface_lock — serialises access to seqno, credits and the response metadata. one at a time, babe, no shoving 💅
• new_epoch — flags the start of day, or the start of MC reboot recovery 🌅
• credits — how many spurious MCDI completion events we'll tolerate before we trigger a fatal error 💀 like, there is a limit
• seqno — the next sequence number to use for mcdi requests, keeping everything in order fr fr
• resprc — response error/success code (Linux numbering) 🍓
• resp_hdr_len — response header length
• resp_data_len — response data (SDU or error) length
• async_lock — serialises access to async_list while event processing is enabled 🔒
• async_list — the queue of asynchronous requests, lined up like it's a queue for a pop-up 🌈
• async_timer — timer for asynchronous request timeout ⏰
• logging_buffer — a buffer that may be used to build MCDI tracing messages; lowkey the journal 📓
• logging_enabled — whether to trace MCDI. on or off, that's the whole question 🦋
• proxy_rx_handle — the most recently received proxy authorisation handle 🎀
• proxy_rx_status — status of the most recent proxy authorisation ⭐
• proxy_rx_wq — wait queue for updates to proxy_rx_handle 🫶

🎀 SEE ALSO 🎀

• Kernel file ./drivers/net/ethernet/sfc/siena/mcdi.h enum
• efx_mcdi_state(9)
• efx_mcdi_mode(9)
• struct efx_mcdi_data(9)

and that's the tea ☕ this iconic lil page lives in ./drivers/net/ethernet/sfc/siena, dated October 2026, and it's literally titled struct efx_mcdi_iface(9) — go read the source bestie, iykyk 💜🌸