STRUCT HSI_MSG(9)

✨ struct hsi_msg(9) ✨

okay so this is a page straight outta the Kernel API Manual — it's the whole glow-up guide to struct hsi_msg, aka the HSI message descriptor. bestie, this is literally the little envelope your data gets stuffed into before it goes zooming down an HSI line. let's get into it 💌

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🌸 NAME 🌸

struct hsi_msg — the HSI message descriptor, no cap ✨

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🦋 SYNOPSIS 🦋

here's the whole struct, copy-paste energy, do not touch the formatting she's fragile:

struct hsi_msg {
    struct list_head        link;
    struct hsi_client       *cl;
    struct sg_table         sgt;
    void *context;
    void (*complete)(struct hsi_msg *msg);
    void (*destructor)(struct hsi_msg *msg);
    int status;
    unsigned int            actual_len;
    unsigned int            channel;
    unsigned int            ttype:1;
    unsigned int            break_frame:1;
 };

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🎀 Members 🎀

every field, one by one, because we do not skip ✨

• link — this one is free real estate 💅 it's totally up to whoever currently owns the descriptor to use it however they want.
• cl — the HSI device client that's issuing the transfer. the main character who hit send, basically 👑
• sgt — head of the scatterlist array. this is where your buffers live 🧺
• context — client context data that's associated to the transfer. your little side-quest payload 🎒
• complete — the transfer completion callback. she gets called when the transfer is done, periodt 📣
• destructor — the destructor, there to free resources when flushing 🧹
• status — status of the transfer once it's completed. the vibe check of the whole operation 🌈
• actual_len — actual length of the data transferred on completion. not the length you hoped for, the length you got 😭
• channel — the channel where the message is gonna TX/RX 📡
• ttype — transfer type: TX if set, RX otherwise. binary icon behaviour honestly 🔥
• break_frame — if true, HSI will send/receive a break frame. and heads up > ⚠️ the data buffers are ignored in the request when this is set, so don't be out here expecting your buffers to do anything 🫶

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💜 SEE ALSO 💜

go read these next, bestie, they're all in the kernel file ./include/linux/hsi/hsi.h — iykyk:

• struct hsi_channel(9)
• struct hsi_config(9)
• struct hsi_board_info(9)
• struct hsi_client(9)
• struct hsi_client_driver(9)
• struct hsi_port(9)
• struct hsi_controller(9)
• hsi_id(9)
• hsi_port_id(9)
• hsi_setup(9)
• hsi_flush(9)
• hsi_async_read(9)
• hsi_async_write(9)
• hsi_start_tx(9)
• hsi_stop_tx(9)

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and that's the whole page, mwah 💋 this lil number lives in ./include/linux/hsi and it's dated October 2026 — signed, sealed, delivered, struct hsi_msg(9) out 🫶✨