dwc2_unreserve_timer_fn(9)

💅 dwc2_unreserve_timer_fn(9) — from the Kernel API Manual, bestie 🎀

okay so this is a kernel API page, straight out of the Kernel API Manual, and it's literally about one little timer callback that politely waits before it lets go of a bandwidth reservation. tiny function, big manners. let's get into it ✨

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🌸 NAME 🌸

dwc2_unreserve_timer_fn — the timer function that releases the periodic reservation 🕐💖

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✨ SYNOPSIS ✨

void dwc2_unreserve_timer_fn (struct timer_list *t );

that's it. one arg, returns nothing, does its little job. no cap. 🫶

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🎀 ARGUMENTS 🎀

• t — address to a qh unreserve_work. (yes bestie, that's the whole description, it's giving minimalism 💅)

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🔥 DESCRIPTION 🔥

so here's the tea ☕ — the kernel doc for usb_submit_urb has this whole section about "Reserved Bandwidth Transfers", and according to that, we need to keep a reservation active for as long as a device driver keeps submitting. like, if the driver's still going, we can't just yank the reservation out from under it. rude. 🙈

and because we're using HCD_BH to give back the URB, we gotta give the driver a little bit of time before we release the reservation. just a lil grace period, y'know? 🧚

this worker is the one that gets called after that appropriate delay. it's the "okay fine, now you can have it back" moment. iconic behavior honestly 👑

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💜 SEE ALSO 💜

• 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_check_max_xfer_size(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)

like, that's the whole friend group right there. go say hi. 🦋

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and that's the page!! 🌈 this lil icon comes from ./drivers/usb/dwc2, dated October 2026, and it lives in the Kernel API Manual — mwah, bye bestie, go read your kernel docs 💖🎀✨