usb_calc_bus_time(9)

✨ usb_calc_bus_time(9) ✨

okay bestie, welcome to the Kernel API Manual page for usb_calc_bus_time(9) — this one is short but lowkey iconic 💅

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🎀 NAME 🎀

usb_calc_bus_time — approximate periodic transaction time in nanoseconds ✨

🌸 SYNOPSIS 🌸

the whole signature, no cap:

long usb_calc_bus_time (int speed , int is_input , int isoc , int
       bytecount );

🦋 ARGUMENTS 🦋

• speed — from dev->speed; USB_SPEED_{LOW,FULL,HIGH} 💫
• is_input — true iff the transaction sends data to the host 🫶
• isoc — true for isochronous transactions, false for interrupt ones ⭐
• bytecount — how many bytes in the transaction 🍓

💖 RETURN 💖

Approximate bus time in nanoseconds for a periodic transaction. that’s the vibe, that’s the return value 😌✨

👑 NOTE 👑

See USB 2.0 spec section 5.11.3; only periodic transfers need to be scheduled in software, this function is only used for such scheduling.

fr fr, that’s the whole caveat — don’t forget it 🧚

🌈 SEE ALSO 🌈

Kernel file ./drivers/usb/core/hcd.c and all these besties:

• ascii2desc(9)
• rh_string(9)
• usb_bus_init(9)
• usb_register_bus(9)
• usb_deregister_bus(9)
• register_root_hub(9)
• usb_hcd_link_urb_to_ep(9)
• usb_hcd_check_unlink_urb(9)
• usb_hcd_unlink_urb_from_ep(9)
• usb_hcd_giveback_urb(9)
• usb_hcd_alloc_bandwidth(9)
• usb_hcd_reset_endpoint(9)
• usb_alloc_streams(9)
• usb_free_streams(9)
• usb_hcd_resume_root_hub(9)
• usb_bus_start_enum(9)
• usb_hcd_irq(9)
• usb_hc_died(9)
• usb_create_shared_hcd(9)
• usb_create_hcd(9)
• usb_stop_hcd(9)
• usb_add_hcd(9)
• usb_remove_hcd(9)

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and that’s the page, bestie 💜 source: ./drivers/usb/core · date: October 2026 · usb_calc_bus_time(9) — slay responsibly 🎀✨