read_fifo(9)

💅 read_fifo(9) — Kernel API Manual, but make it make sense 🫶

okay bestie, so this is read_fifo, a kernel API manual page (9 is the kernel section, iykyk), and it's genuinely so good at what it does. sit down, hydrate, let's go ✨

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🌸 NAME 🌸

read_fifo — Transfer packets from OUT endpoint into usb request 💌

(like, it's giving "move the packets out of the fifo and into the request", and that's the whole vibe fr fr)

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🦋 SYNOPSIS 🦋

int read_fifo (struct pxa_ep *ep , struct pxa27x_request *req );

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🎀 ARGUMENTS 🎀

• ep — pxa physical endpoint. she's the ✨physical✨ one, not the logical one, okay 👑
• req — usb request. this is the little container the packets are gonna live in afterward 💖

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🔥 CONTEXT 🔥

interrupt handler 🫶 — yes, you're in interrupt context, not me being dramatic for once. keep it snappy, bestie.

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⭐ DESCRIPTION ⭐

okay so the whole point: unload as many packets as possible from the fifo we use for usb OUT transfers and put them into the request 💅 that's it, that's the function. she's a mover, an icon, a packet relocation specialist.

the caller should have made sure there's at least one packet ready — like, that's on you, not on her 🙈 so do your little vibe check before calling, mmkay?

⚠️ also important: it doesn't complete the request, that's the caller's job. do not expect her to finish that for you, she will not, no cap 💀

and the return values, because we love a clear answer:

• returns 1 if the request completed ✅
• returns 0 otherwise 🫥

periodt.

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🌈 SEE ALSO 🌈

the kernel file is ./drivers/usb/gadget/udc/pxa27x_udc.c and honestly the whole friend group lives there together. here's everyone, no one left out, we don't do that 💜

• is_match_usb_pxa(9)
• find_pxa_ep(9)
• update_pxa_ep_matches(9)
• pio_irq_enable(9)
• pio_irq_disable(9)
• udc_set_mask_UDCCR(9)
• udc_clear_mask_UDCCR(9)
• ep_write_UDCCSR(9)
• ep_count_bytes_remain(9)
• ep_is_empty(9)
• ep_is_full(9)
• epout_has_pkt(9)
• set_ep0state(9)
• ep0_idle(9)
• inc_ep_stats_reqs(9)
• inc_ep_stats_bytes(9)
• pxa_ep_setup(9)
• pxa_eps_setup(9)
• pxa_ep_alloc_request(9)
• pxa_ep_free_request(9)
• ep_add_request(9)
• ep_del_request(9)
• req_done(9)
• ep_end_out_req(9)
• ep0_end_out_req(9)
• ep_end_in_req(9)
• ep0_end_in_req(9)
• nuke(9)
• read_packet(9)
• write_packet(9)
• write_fifo(9)
• read_ep0_fifo(9)
• write_ep0_fifo(9)
• pxa_ep_queue(9)
• pxa_ep_dequeue(9)
• pxa_ep_set_halt(9)
• pxa_ep_fifo_status(9)
• pxa_ep_fifo_flush(9)
• pxa_ep_enable(9)
• pxa_ep_disable(9)
• dplus_pullup(9)
• pxa_udc_get_frame(9)
• pxa_udc_wakeup(9)
• should_enable_udc(9)
• should_disable_udc(9)
• pxa_udc_pullup(9)
• pxa_udc_vbus_session(9)
• pxa_udc_vbus_draw(9)
• pxa_udc_phy_event(9)
• udc_disable(9)
• udc_init_data(9)
• udc_enable(9)
• pxa27x_udc_start(9)
• stop_activity(9)
• pxa27x_udc_stop(9)
• handle_ep0_ctrl_req(9)
• handle_ep0(9)
• handle_ep(9)
• pxa27x_change_configuration(9)
• pxa27x_change_interface(9)
• irq_udc_suspend(9)
• irq_udc_resume(9)
• irq_udc_reconfig(9)
• irq_udc_reset(9)
• pxa_udc_irq(9)
• pxa_udc_probe(9)
• pxa_udc_remove(9)
• pxa_udc_suspend(9)
• pxa_udc_resume(9)

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and that's the page, bestie 🧚 source is ./drivers/usb/gadget/udc, dated October 2026, section read_fifo(9) — mwah, go read the fifo, slay 💅💖