STRUCT FW_CDEV_GET_CYCLE_TIMER(9)

💅 struct fw_cdev_get_cycle_timer(9) 💅

okay bestie, welcome to the Kernel API Manual, section 9 — we're looking at struct fw_cdev_get_cycle_timer today and honestly it's giving tiny-but-mighty. 🎀

---

✨ NAME ✨

struct fw_cdev_get_cycle_timer — read cycle timer register

---

🌸 SYNOPSIS 🌸

struct fw_cdev_get_cycle_timer {
    __u64 local_time;
    __u32 cycle_timer;
 };

---

🦋 Members 🦋

• local_time — the system time, in microseconds since the Epoch. yes that Epoch, the one everyone's counting from 🕰️
• cycle_timer — literally just the contents of the Cycle Time register. iconic. ✨

---

💖 Description 💖

So it's the same thing as FW_CDEV_IOC_GET_CYCLE_TIMER2, no cap — but this one is fixed to use CLOCK_REALTIME and it only does microseconds resolution. that's the vibe, that's the whole personality. 🙈

But wait, spill time: in version 1 and 2 of the ABI, this ioctl returned unreliable (non-monotonic) cycle_timer values on certain controllers. 😭 so if you're poking at old ABI versions, be aware — those numbers were not giving trustworthy.

---

🔥 SEE ALSO 🔥

Kernel file ./include/uapi/linux/firewire-cdev.h (and friends, there are so many friends, bestie):

• struct fw_cdev_event_common(9)
• struct fw_cdev_event_bus_reset(9)
• struct fw_cdev_event_response(9)
• struct fw_cdev_event_response2(9)
• struct fw_cdev_event_request(9)
• struct fw_cdev_event_request2(9)
• struct fw_cdev_event_request3(9)
• struct fw_cdev_event_iso_interrupt(9)
• struct fw_cdev_event_iso_interrupt_mc(9)
• struct fw_cdev_event_iso_resource(9)
• struct fw_cdev_event_phy_packet(9)
• struct 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_queue_iso(9)
• struct fw_cdev_start_iso(9)
• struct fw_cdev_stop_iso(9)
• struct fw_cdev_flush_iso(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)

---

ngl the whole gang's here — go read the rest of them, iykyk 🫶

---

that's the whole page, bestie, you ate that. coming to you from ./include/uapi/linux, dated October 2026, filed under struct fw_cd..._cycle_timer(9) — mwah 💅💖⭐