pch_udc_free_dma_chain(9)

📦 version 7.3.1, in nixpkgs unstable

💅 pch_udc_free_dma_chain — Kernel API Manual ✨

okay so bestie, welcome to the pch_udc_free_dma_chain(9) page 💖 this is the part of the kernel API manual where we talk about cleaning up — yes, the unglamorous but lowkey iconic part where the DMA chain for a request gets freed. no leaks, no leftovers, no mess. slay. 🎀

✨ NAME ✨

pch_udc_free_dma_chain — this function frees the DMA chain created for the request 🧹💫

like, it's literally the cleanup crew. the request's DMA chain has done its job and now it gets to rest. no cap.

🦋 SYNOPSIS 🦋

void pch_udc_free_dma_chain (struct pch_udc_dev *dev , struct
pch_udc_request *req );
heads up: it's a void function, so there's nothing coming back at you. you call it, it does the freeing, you move on with your life. periodt. 💅

🌸 ARGUMENTS 🌸

  • dev — a reference to the driver structure 🫶 your pointer into the pch_udc_dev world.
  • req — a reference to the request that's getting freed 💜 this is the one being sent off into the void.

bestie please pass real, valid references. the manpage doesn't get spicy about it, and neither will I, but like… yeah. 🙈

⭐ DESCRIPTION ⭐

so here's the whole vibe: this function frees the DMA chain that was created for the request. that's it. that's the tea. 🍓

Return codes: 0: Success 🎉

ngl the fact that a void function is out here documenting return codes is giving main character energy and I respect it 😭 but that's what the page says, so that's what you get. 0 means success. we love a zero. we stan a zero. ✅

🌈 SEE ALSO 🌈

okay this list is long long, so buckle up bestie — every single one of these is part of the pch_udc cinematic universe 🦋 the kernel file is ./drivers/usb/gadget/udc/pch_udc.c, and the structs kick things off:

struct pch_udc_data_dma_desc(9), struct pch_udc_stp_dma_desc(9), struct pch_udc_cfg_data(9), struct pch_udc_ep(9), struct pch_vbus_gpio_data(9), struct pch_udc_dev(9), struct pch_udc_request(9)

then the CSR + wakeup + frame + selfpowered + disconnect crew 💫

pch_udc_csr_busy(9), pch_udc_write_csr(9), pch_udc_read_csr(9), pch_udc_rmt_wakeup(9), pch_udc_get_frame(9), pch_udc_clear_selfpowered(9), pch_udc_set_selfpowered(9), pch_udc_set_disconnect(9), pch_udc_clear_disconnect(9), pch_udc_reconnect(9), pch_udc_vbus_session(9)

the endpoint girlies 👑 (stall, transfer type, buffer size, max packet, subptr, ddptr, pd, rrdy):

pch_udc_ep_set_stall(9), pch_udc_ep_clear_stall(9), pch_udc_ep_set_trfr_type(9), pch_udc_ep_set_bufsz(9), pch_udc_ep_set_maxpkt(9), pch_udc_ep_set_subptr(9), pch_udc_ep_set_ddptr(9), pch_udc_ep_set_pd(9), pch_udc_ep_set_rrdy(9), pch_udc_ep_clear_rrdy(9)

DMA + interrupts + status/control/EP registers, aka the whole tech-deck 🔥:

pch_udc_set_dma(9), pch_udc_clear_dma(9), pch_udc_set_csr_done(9), pch_udc_disable_interrupts(9), pch_udc_enable_interrupts(9), pch_udc_disable_ep_interrupts(9), pch_udc_enable_ep_interrupts(9), pch_udc_read_device_interrupts(9), pch_udc_write_device_interrupts(9), pch_udc_read_ep_interrupts(9), pch_udc_write_ep_interrupts(9), pch_udc_read_device_status(9), pch_udc_read_ep_control(9), pch_udc_clear_ep_control(9), pch_udc_read_ep_status(9), pch_udc_clear_ep_status(9), pch_udc_ep_set_nak(9), pch_udc_ep_clear_nak(9), pch_udc_ep_fifo_flush(9), pch_udc_ep_enable(9), pch_udc_ep_disable(9), pch_udc_wait_ep_stall(9)

init/exit and the peripheral-controller-driver (pcd) glow-up ✨:

pch_udc_init(9), pch_udc_exit(9), pch_udc_pcd_get_frame(9), pch_udc_pcd_wakeup(9), pch_udc_pcd_selfpowered(9), pch_udc_pcd_pullup(9), pch_udc_pcd_vbus_session(9), pch_udc_pcd_vbus_draw(9)

the vbus gpio squad 🌈:

pch_vbus_gpio_get_value(9), pch_vbus_gpio_work_fall(9), pch_vbus_gpio_work_rise(9), pch_vbus_gpio_irq(9), pch_vbus_gpio_init(9), pch_vbus_gpio_free(9)

request handling + DMA chain creation (hey, that's our function's sibling!! 💖):

complete_req(9), empty_req_queue(9), pch_udc_create_dma_chain(9), prepare_dma(9), process_zlp(9), pch_udc_start_rxrequest(9)

the pcd endpoint + request API 🎀:

pch_udc_pcd_ep_enable(9), pch_udc_pcd_ep_disable(9), pch_udc_alloc_request(9), pch_udc_free_request(9), pch_udc_pcd_queue(9), pch_udc_pcd_dequeue(9), pch_udc_pcd_set_halt(9), pch_udc_pcd_set_wedge(9), pch_udc_pcd_fifo_flush(9)

transfer + service routines, the ones doing the actual work 😤:

pch_udc_init_setup_buff(9), pch_udc_start_next_txrequest(9), pch_udc_complete_transfer(9), pch_udc_complete_receiver(9), pch_udc_svc_data_in(9), pch_udc_svc_data_out(9), pch_udc_svc_control_in(9), pch_udc_svc_control_out(9), pch_udc_postsvc_epinters(9), pch_udc_read_all_epstatus(9), pch_udc_activate_control_ep(9), pch_udc_svc_ur_interrupt(9), pch_udc_svc_enum_interrupt(9), pch_udc_svc_intf_interrupt(9), pch_udc_svc_cfg_interrupt(9)

and finally the ISR + init/reinit + dma pool crew, closing us out 💜:

pch_udc_dev_isr(9), pch_udc_isr(9), pch_udc_setup_ep0(9), pch_udc_pcd_reinit(9), pch_udc_pcd_init(9), init_dma_pools(9)

iykyk 💅

fr fr though — if you're here reading a kernel DMA cleanup page, you're already kind of a legend. go free those chains. 🫶

and that's the page!! 🎀 this one lives under ./drivers/usb/gadget/udc in the Kernel API Manual, last touched October 2026 — mwah, go touch some grass (or some pch_udc source) bestie, ily, bye!! 💖✨🦋

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