dwc2_check_max_xfer_size(9)

✨ NAME ✨

okay so bestie, this is dwc2_check_max_xfer_size(9), and it comes straight from the Kernel API Manual 🫶. Its whole thing is checking that the max transfer size allowed in a host channel is large enough to handle the maximum data transfer in a single (micro)frame for a periodic transfer ✨. That's the vibe, and it's lowkey iconic.

🌸 SYNOPSIS 🌸

int dwc2_check_max_xfer_size (struct dwc2_hsotg *hsotg , struct dwc2_qh *qh );

No cap, that's the exact signature — do not come for me about the spaces 💅.

🎀 ARGUMENTS 🎀

• hsotg — the HCD state structure for the DWC OTG controller. It's giving "main character state struct" energy 👑.
• qh — QH for a periodic endpoint. Yep, that's the periodic-endpoint QH, bestie 🦋.

💖 RETURN 💖

0 if successful ✅, negative error code otherwise 😭. So like, happy path gets a zero, bad path gets a negative code — periodt.

🌈 SEE ALSO 🌈

the extended universe, fr fr — go read these:

• Kernel file ./drivers/usb/dwc2/hcd_queue.c
• dwc2_periodic_channel_available(9)
• dwc2_check_periodic_bandwidth(9)
• pmap_schedule(9)
• pmap_unschedule(9)
• dwc2_get_ls_map(9)
• dwc2_qh_print(9)
• dwc2_qh_schedule_print(9)
• dwc2_ls_pmap_schedule(9)
• dwc2_ls_pmap_unschedule(9)
• dwc2_hs_pmap_schedule(9)
• dwc2_hs_pmap_unschedule(9)
• dwc2_uframe_schedule_split(9)
• dwc2_uframe_schedule_hs(9)
• dwc2_uframe_schedule_ls(9)
• dwc2_uframe_schedule(9)
• dwc2_uframe_unschedule(9)
• dwc2_pick_first_frame(9)
• dwc2_do_reserve(9)
• dwc2_do_unreserve(9)
• dwc2_unreserve_timer_fn(9)
• dwc2_schedule_periodic(9)
• dwc2_deschedule_periodic(9)
• dwc2_wait_timer_fn(9)
• dwc2_qh_init(9)
• dwc2_hcd_qh_create(9)
• dwc2_hcd_qh_free(9)
• dwc2_hcd_qh_add(9)
• dwc2_hcd_qh_unlink(9)
• dwc2_next_for_periodic_split(9)
• dwc2_next_periodic_start(9)
• dwc2_hcd_qtd_init(9)
• dwc2_hcd_qtd_add(9)

source/version: ./drivers/usb/dwc2 · October 2026 · from the Kernel API Manual — mwah, bestie 💋🫶