STRUCT TBSTREAM_DEV(9)

💅 struct tbstream_dev(9) — the Kernel API Manual, bestie edition

okay so this one lives in the kernel API manual and it's literally all about struct tbstream_dev, aka the stream character device. yes bestie, the character device that does the tunneling. let's get into it 🎀

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✨ NAME ✨

struct tbstream_dev — Stream character device. that's it, that's the vibe. 🦋

🌸 SYNOPSIS 🌸

here's the whole struct, character for character, no cap:

struct tbstream_dev {
    struct config_group group;
    struct tbstream *stream;
    struct miscdevice misc;
    struct kref kref;
    int index;
    int in_hopid;
    int out_hopid;
    unsigned int ring_size;
    unsigned int throttling;
    bool busy_poll;
    int users;
    bool closed;
    bool removed;
    wait_queue_head_t wait;
    struct mutex lock;
    struct tbstream_ring tx_ring;
    struct tbstream_ring rx_ring;
    struct list_head list;
 };

yes there are two whole rings, we stan 💅

👑 Members 👑

lowkey the most important part, so let's go member by member, no skipping, fr fr ✨

• group — the ConfigFS group for this device. it's giving organizational queen 👑
• stream — pointer to the stream if it's attached, and NULL otherwise. so check it before you dereference it, bestie, i'm begging 😭
• misc — the character device used for tunneling. main character energy, honestly
• kref — the reference count. keep it balanced or things get ugly 💀
• index — a unique identifier for the character device. every device needs its own little name tag 🎀
• in_hopid — the In HopID
• out_hopid — the Out HopID. in and out, balanced, iconic 🌈
• ring_size — the size of the rings
• throttling — interrupt throttling rate in ns. yes, nanoseconds, we're precise here ⭐
• busy_poll — instead of interrupts, busy poll the rings. different strategy, same energy 🔥
• users — number of times cdev has been opened
• closed — set when a CLOSE packet was received
• removed — userspace removed the ConfigFS group underneath. rude but okay 🙈
• wait — waitqueue for open, read and write. it's where everyone waits their turn 🫶
• lock — the lock protecting this structure. do not skip the lock, i'm serious 💀
• tx_ring — transmit ring
• rx_ring — receive ring
• list — stream devices are linked through this. friendship bracelet behavior, honestly 💖

🧚 SEE ALSO 🧚

go read these next, iykyk:

• Kernel file ./drivers/thunderbolt/stream.c
• enum tbstream_frame_pdf(9)
• struct tbstream_frame(9)
• struct tbstream_ring(9)
• struct tbstream_group(9)
• struct tbstream(9)

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ok that's the whole page, no gatekeeping 💅 go forth and tunnel responsibly, bestie. and remember: stream can be NULL, take the lock, and check that kref 🫶

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and that's a wrap! this iconic little doc comes from ./drivers/thunderbolt in the Kernel API Manual, dated October 2026. slay, periodt, bye! 🌸✨💜