STRUCT IPC_PIPE(9)

💖 NAME 💖

okay so bestie, welcome to the struct ipc_pipe(9) page from the Kernel API Manual — this is literally the Structure for Pipe, and that's the whole vibe. 💅 no cap.

✨ SYNOPSIS ✨

here's the struct in all its glory — copy-paste exact, no edits, please and thank you 🫶:

struct ipc_pipe {
    struct ipc_protocol_td *tdr_start;
    struct ipc_mem_channel *channel;
    struct sk_buff **skbr_start;
    dma_addr_t phy_tdr_start;
    u32 old_head;
    u32 old_tail;
    u32 nr_of_entries;
    u32 max_nr_of_queued_entries;
    u32 accumulation_backoff;
    u32 irq_moderation;
    u32 pipe_nr;
    u32 irq;
    enum ipc_mem_pipe_dir dir;
    u32 buf_size;
    u16 nr_of_queued_entries;
    u8 is_open:1;
 };

🫶 Members 🫶

okay bestie, here's the member-by-member tea ☕ — every field, every detail, all iconic:

• tdr_start — Ipc private protocol Transfer Descriptor Ring. yes, capital-letter TDR energy.
• channel — Id of the sio device, set by imem_sio_open, needed to pass DL char to the user terminal.
• skbr_start — Circular buffer for skbuf and the buffer reference in a tdr_start entry.
• phy_tdr_start — Transfer descriptor start address.
• old_head — last head pointer reported to CP.
• old_tail — AP read position before CP moves the read position to write/head. If CP has consumed the buffers, AP has to freed the skbuf starting at tdr_start[old_tail].
• nr_of_entries — Number of elements of skb_start and tdr_start.
• max_nr_of_queued_entries — Maximum number of queued entries in TDR.
• accumulation_backoff — Accumulation in usec for accumulation backoff (0 = no acc backoff).
• irq_moderation — timer in usec for irq_moderation (0=no irq moderation).
• pipe_nr — Pipe identification number.
• irq — Interrupt vector.
• dir — Direction of data stream in pipe.
• buf_size — Buffer size (in bytes) for preallocated buffers (for DL pipes).
• nr_of_queued_entries — “Aueued number of entries” — yes, that's the spelling in the source, we're not fixing it, it's part of the lore 💀.
• is_open — Check for open pipe status.

🌈 SEE ALSO 🌈

Kernel file: ./drivers/net/wwan/iosm/iosm_ipc_imem.h — and now the whole bestie reference list, zero skips, fr fr:

• enum ipc_ctype(9)
• struct ipc_mem_channel(9)
• enum ipc_phase(9)
• struct iosm_imem(9)
• ipc_imem_init(9)
• ipc_imem_pm_s2idle_sleep(9)
• ipc_imem_pm_suspend(9)
• ipc_imem_pm_resume(9)
• ipc_imem_cleanup(9)
• ipc_imem_irq_process(9)
• imem_get_device_sleep_state(9)
• ipc_imem_td_update_timer_suspend(9)
• ipc_imem_channel_close(9)
• ipc_imem_channel_alloc(9)
• ipc_imem_channel_open(9)
• ipc_imem_td_update_timer_start(9)
• ipc_imem_ul_write_td(9)
• ipc_imem_ul_send(9)
• ipc_imem_channel_update(9)
• ipc_imem_channel_free(9)
• ipc_imem_hrtimer_stop(9)
• ipc_imem_pipe_cleanup(9)
• ipc_imem_pipe_close(9)
• ipc_imem_phase_update(9)
• ipc_imem_phase_get_string(9)
• ipc_imem_msg_send_feature_set(9)
• ipc_imem_ipc_init_check(9)
• ipc_imem_channel_init(9)
• ipc_imem_devlink_trigger_chip_info(9)

okay that's the whole page bestie 💖 this little masterpiece lives under ./drivers/net/wwan/iosm, dated October 2026, and it's literally struct ipc_pipe(9) core 🎀✨