STRUCT FW_CDEV_QUEUE_ISO(9)

🎀 struct fw_cdev_queue_iso(9) 🎀

okay so this is a page from the Kernel API Manual — yes, that Kernel API Manual, the firewire-cdev one — and it's all about struct fw_cdev_queue_iso. bestie, this is the "queue up your isochronous packets for I/O" struct and honestly it's giving main character energy in the firewire world 💅

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✨ NAME ✨

struct fw_cdev_queue_iso — Queue isochronous packets for I/O 🦋

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🌸 SYNOPSIS 🌸

struct fw_cdev_queue_iso {
    __u64 packets;
    __u64 data;
    __u32 size;
    __u32 handle;
 };

like literally that's the whole shape of it, no cap ✨

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💖 Members 💖

• packets — a userspace pointer to an array of fw_cdev_iso_packet. yes bestie, userspace, it's pointing at your array 👑
• data — a pointer into the mmap'ed payload buffer. mmap'ed, remember it 🫶
• size — the size of the packets array, in bytes. bytes, not packets, okurrr 📏
• handle — the isochronous context handle. it's giving "ticket to the iso party" 🎟️

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🔥 Description 🔥

So what does it do? It queues a number of isochronous packets for reception or transmission. either direction, she's versatile 💅

This ioctl takes a pointer to an array of fw_cdev_iso_packet structs, which describe how to transmit from or receive into a contiguous region of a mmap'ed payload buffer. contiguous region, mmap'ed buffer, got it? 🧚

And here's the cute part: as part of transmit packet descriptors, a series of headers can be supplied, and those will be prepended to the payload during DMA. headers first, payload after, slay 🌈

lowkey important caveat: the kernel may or may not queue all packets. not all of them, maybe. but it will write back updated values of the packets, data and size fields — so the ioctl can be resubmitted easily. ngl that resubmit-friendliness is iconic, it ate 💀

also a real one: in case of a multichannel receive context, data must be quadlet-aligned relative to the buffer start. quadlet-aligned, relative to buffer start, don't forget it or it's over 🙈

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🌟 SEE ALSO 🌟

Kernel file ./include/uapi/linux/firewire-cdev.h struct, plus the whole friend group 👇

• fw_cdev_event_common(9)
• fw_cdev_event_bus_reset(9)
• fw_cdev_event_response(9)
• fw_cdev_event_response2(9)
• fw_cdev_event_request(9)
• fw_cdev_event_request2(9)
• fw_cdev_event_request3(9)
• fw_cdev_event_iso_interrupt(9)
• fw_cdev_event_iso_interrupt_mc(9)
• fw_cdev_event_iso_resource(9)
• fw_cdev_event_phy_packet(9)
• fw_cdev_event_phy_packet2(9)
• union fw_cdev_event(9)
• struct fw_cdev_get_info(9)
• struct fw_cdev_send_request(9)
• struct fw_cdev_send_response(9)
• struct fw_cdev_allocate(9)
• struct fw_cdev_deallocate(9)
• struct fw_cdev_initiate_bus_reset(9)
• struct fw_cdev_add_descriptor(9)
• struct fw_cdev_remove_descriptor(9)
• struct fw_cdev_create_iso_context(9)
• struct fw_cdev_set_iso_channels(9)
• struct fw_cdev_iso_packet(9)
• struct fw_cdev_start_iso(9)
• struct fw_cdev_stop_iso(9)
• struct fw_cdev_flush_iso(9)
• struct fw_cdev_get_cycle_timer(9)
• struct fw_cdev_get_cycle_timer2(9)
• struct fw_cdev_allocate_iso_resource(9)
• struct fw_cdev_send_stream_packet(9)
• struct fw_cdev_send_phy_packet(9)
• struct fw_cdev_receive_phy_packets(9)

like, the whole squad showed up for this one 😭💜

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and that's the page, bestie! this one lives in ./include/uapi/linux, dated October 2026, and the manual name is struct fw_cdev_queue_iso(9) in case you forgot already 🍓 go queue some packets, you absolute icon ⭐💅