STRUCT ACPM_CHAN_SHMEM(9)

💖 NAME 💖

struct acpm_chan_shmem — okay so this is literally the descriptor of a shared memory channel, bestie. That's the whole vibe. 🦋

(also hi, this is the acpm_chan_shmem(9) page from the Kernel API Manual, mwah 💅)

✨ SYNOPSIS ✨

Here's the struct in all its glory — copy it exactly, do not touch, she is perfect as she is:

struct acpm_chan_shmem {
    u32 id;
    u32 reserved[3];
    u32 rx_rear;
    u32 rx_front;
    u32 rx_base;
    u32 reserved1[3];
    u32 tx_rear;
    u32 tx_front;
    u32 tx_base;
    u32 qlen;
    u32 mlen;
    u32 reserved2[2];
    u32 poll_completion;
 };

🎀 MEMBERS 🎀

Every field, no skips, we're doing a full tour 💜

• id — the channel ID. her government name, basically.
• reserved — unused fields. they're just vibing, don't bother them.
• rx_rear — rear pointer of the APM RX queue (that's the TX queue for AP, iykyk).
• rx_front — front pointer of the APM RX queue (TX for AP).
• rx_base — base address of the APM RX queue (TX for AP).
• reserved1 — more unused fields. slay, they're decorative 🎀
• tx_rear — rear pointer of the APM TX queue (which is the RX queue for AP).
• tx_front — front pointer of the APM TX queue (RX for AP).
• tx_base — base address of the APM TX queue (RX for AP).
• qlen — queue length, and it applies to both the TX and RX queues. equal opportunity queen 👑
• mlen — message length, also applies to both TX and RX queues.
• reserved2 — unused fields, yes again, it's a whole thing.
• poll_completion — true when the channel works on polling. that's it, that's the field 🌸

heads up bestie: the direction flips between APM and AP for the rx/tx pointers — rx_* is the APM RX queue but the AP TX queue, and tx_* is the APM TX queue but the AP RX queue. don't mix them up or it's giving chaos 😭

🌈 SEE ALSO 🌈

the whole friend group, fr fr — go read these next:

• Kernel file ./drivers/firmware/samsung/exynos-acpm.c
• struct acpm_shmem(9)
• struct acpm_queue(9)
• struct acpm_rx_data(9)
• struct acpm_chan(9)
• struct acpm_info(9)
• struct acpm_match_data(9)
• acpm_get_saved_rx(9)
• acpm_get_rx(9)
• acpm_dequeue_by_polling(9)
• acpm_wait_for_queue_slots(9)
• acpm_prepare_xfer(9)
• acpm_wait_for_message_response(9)
• acpm_do_xfer(9)
• acpm_set_xfer(9)
• acpm_chan_shmem_get_params(9)
• acpm_achan_alloc_cmds(9)
• acpm_free_mbox_chans(9)
• acpm_channels_init(9)
• acpm_handle_put(9)
• devm_acpm_release(9)
• acpm_get_by_node(9)
• devm_acpm_get_by_node(9)
• devm_acpm_get_by_phandle(9)

and that's the page!! 🫶 brought to you by the source in ./drivers/firmware/samsung, stamped October 2026, and yes the footer still says struct acpm_chan_shmem(9) because she's the main character of her own manpage 💅✨