dwc2_queue_transaction(9)

✨ dwc2_queue_transaction ✨

okay bestie, welcome to the dwc2_queue_transaction(9) page from the Kernel API Manual 💅 this one's a little kernel function that tries to queue up ONE single transaction request — just one! — for a host channel that's tied to either a periodic or a non-periodic transfer. that's the whole vibe. 🎀

---

🌸 NAME 🌸

dwc2_queue_transaction — attempts to queue a single transaction request for a host channel associated with either a periodic or non-periodic transfer 🦋

---

✨ SYNOPSIS ✨

int dwc2_queue_transaction (struct dwc2_hsotg *hsotg , struct
dwc2_host_chan *chan , u16 fifo_dwords_avail );

---

💖 ARGUMENTS 💖

• hsotg — the HCD state structure 🫶 like, the main character state blob
• chan — host channel descriptor associated with either a periodic or a non-periodic transfer
• fifo_dwords_avail — number of DWORDs available in the periodic Tx FIFO for periodic transfers, or the non-periodic Tx FIFO for non-periodic transfers 🍓 (yes, it's a different FIFO depending on your transfer type, keep up bestie)

---

⭐ RETURN ⭐

• 1 — a request got queued, and more requests may be needed to complete the transfer 👑 (there's more work to do, slay)
• 0 — no more requests are required for this transfer, we're done here periodt
• -1 — there is insufficient space in the Tx FIFO 😭 the vibes are not immaculate, the FIFO said no

---

🦋 DESCRIPTION 🦋

so this function assumes there is space available in the appropriate request queue. like, it's trusting you on that one, no cap. 🙈

for an OUT transfer or a SETUP transaction in Slave mode, it checks whether space is available in the appropriate Tx FIFO. so it does an actual vibe check on the FIFO for those cases 💅

⚠️ must be called with interrupt disabled AND spinlock held. both. not one, both. this is not optional and I am not joking around about it 🔥

---

🌈 SEE ALSO 🌈

kernel file ./drivers/usb/dwc2/hcd.c and honestly the whole friend group:

• dwc2_enable_common_interrupts(9)
• dwc2_enable_host_interrupts(9)
• dwc2_disable_host_interrupts(9)
• dwc2_calc_frame_interval(9)
• dwc2_read_packet(9)
• dwc2_dump_channel_info(9)
• dwc2_hc_init(9)
• dwc2_hc_halt(9)
• dwc2_hc_cleanup(9)
• dwc2_hc_set_even_odd_frame(9)
• dwc2_hc_write_packet(9)
• dwc2_hc_do_ping(9)
• dwc2_hc_start_transfer(9)
• dwc2_hc_start_transfer_ddma(9)
• dwc2_hc_continue_transfer(9)
• dwc2_hcd_start(9)
• dwc2_hcd_connect(9)
• dwc2_hcd_disconnect(9)
• dwc2_hcd_rem_wakeup(9)
• dwc2_hcd_stop(9)
• dwc2_core_init(9)
• dwc2_core_host_init(9)
• dwc2_assign_and_init_hc(9)
• dwc2_hcd_select_transactions(9)
• dwc2_hcd_queue_transactions(9)
• dwc2_port_suspend(9)
• dwc2_port_resume(9)
• dwc2_host_get_tt_info(9)
• dwc2_host_put_tt_info(9)
• dwc2_backup_host_registers(9)
• dwc2_restore_host_registers(9)
• dwc2_host_enter_hibernation(9)
• dwc2_host_enter_partial_power_down(9)
• dwc2_host_enter_clock_gating(9)
• dwc2_host_exit_clock_gating(9)

---

okay that's the whole page, you ate that fr fr 💜 this iconic little entry lives under ./drivers/usb/dwc2 and it's dated October 2026 — so yeah, mark your calendar bestie, and remember: interrupts off, spinlock held, and the FIFO's the one who decides. 🧚‍♀️✨🫶