STRUCT TB_RING(9)

🦋 struct tb_ring(9) — Kernel API Manual 🦋

💖 NAME 💖

struct tb_ring — the thunderbolt TX or RX ring associated with a NHI. It’s giving “ring buffer but make it Thunderbolt,” and honestly? Obsessed 💅.

✨ SYNOPSIS ✨

struct tb_ring {
    spinlock_t lock;
    struct tb_nhi *nhi;
    int size;
    int hop;
    int head;
    int tail;
    struct ring_desc *descriptors;
    dma_addr_t descriptors_dma;
    struct list_head queue;
    struct list_head in_flight;
    struct work_struct work;
    bool is_tx:1;
    bool running:1;
    int irq;
    u8 vector;
    unsigned int flags;
    int e2e_tx_hop;
    u16 sof_mask;
    u16 eof_mask;
    void (*start_poll)(void *data);
    void *poll_data;
    unsigned int interval_nsec;
    wait_queue_head_t wait;
    struct lock_class_key lock_key;
};

🌸 MEMBERS 🌸

Okay bestie, every field here is a little main character, so let’s do the full tour 🫶:

• lock — the lock that serializes actions to this ring. No cap, it must be acquired after nhi->lock 🔒.
• nhi — pointer to the native host controller interface.
• size — size of the ring.
• hop — hop (DMA channel) associated with this ring.
• head — head of the ring (write next descriptor here).
• tail — tail of the ring (complete next descriptor here).
• descriptors — allocated descriptors for this ring.
• descriptors_dma — DMA address of descriptors for this ring.
• queue — queue holding frames to be transferred over this ring.
• in_flight — queue holding frames that are currently in flight.
• work — interrupt work structure.
• is_tx — is the ring Tx or Rx.
• running — is the ring running.
• irq — MSI-X irq number if the ring uses MSI-X. 0 otherwise.
• vector — MSI-X vector number the ring uses (only set if irq is > 0).
• flags — ring specific flags.
• e2e_tx_hop — transmit HopID when E2E is enabled. Only applicable to RX ring. For TX ring this should be set to 0.
• sof_mask — bit mask used to detect start of frame PDF.
• eof_mask — bit mask used to detect end of frame PDF.
• start_poll — called when ring interrupt is triggered to start polling. Passing NULL keeps the ring in interrupt mode.
• poll_data — data passed to start_poll.
• interval_nsec — interval counter if interrupt throttling is to be used with this ring (in ns).
• wait — used to signal that the ring may be empty now.
• lock_key — lock validator class key per-ring.

🔥 SEE ALSO 🔥

Go touch grass in the kernel tree, bestie — the related squad is right here 🌈:

• Kernel file ./include/linux/thunderbolt.h
• enum tb_security_level(9)
• struct tb(9)
• struct tb_property_dir(9)
• struct tb_property(9)
• enum tb_link_width(9)
• struct tb_xdomain(9)
• struct tb_protocol_handler(9)
• struct tb_service(9)
• struct tb_service_driver(9)
• struct tb_nhi(9)
• enum ring_desc_flags(9)
• struct ring_frame(9)
• tb_ring_rx(9)
• tb_ring_tx(9)
• tb_ring_dma_device(9)

Source: ./include/linux · Date: October 2026 · Page: struct tb_ring(9) — that’s the footer, bestie, bye and stay slaying 💖🎀