usb_ep_fifo_status(9)

💅 usb_ep_fifo_status(9) — Kernel API Manual 💅

okay bestie, welcome to the Kernel API Manual page for usb_ep_fifo_status(9) — the way that this call just returns a number of bytes or an error is literally giving main character energy. no cap. 🫶

💖 NAME 💖

usb_ep_fifo_status — returns number of bytes in fifo, or error. that's the whole vibe check, bestie. ✨

🎀 SYNOPSIS 🎀

int usb_ep_fifo_status (struct usb_ep *ep );

🌸 ARGUMENTS 🌸

• ep — the endpoint whose fifo status is being checked. this is the endpoint you're side-eyeing, bestie. 👀

🦋 DESCRIPTION 🦋

okay so FIFO endpoints may have "unclaimed data" in them in certain cases, such as after aborted transfers. 😭 hosts may not have collected all the IN data written by the gadget driver (and reported by a request completion). and the gadget driver may not have collected all the data written OUT to it by the host. so drivers that need precise handling for fault reporting or recovery may need to use this call. fr fr. 🛠️

the good news: this routine may be called in interrupt context. 💅

this returns the number of such bytes in the fifo, or a negative errno if the endpoint doesn't use a FIFO or doesn't support such precise handling. that's the tea. 🍵

🌈 SEE ALSO 🌈

go read these next, bestie — the whole squad is here: 🫶

• Kernel file ./drivers/usb/gadget/udc/core.c
• struct usb_udc(9)
• usb_ep_set_maxpacket_limit(9)
• usb_ep_enable(9)
• usb_ep_disable(9)
• usb_ep_alloc_request(9)
• usb_ep_free_request(9)
• usb_ep_queue(9)
• usb_ep_dequeue(9)
• usb_ep_set_halt(9)
• usb_ep_clear_halt(9)
• usb_ep_set_wedge(9)
• usb_ep_fifo_flush(9)
• usb_gadget_frame_number(9)
• usb_gadget_wakeup(9)
• usb_gadget_set_remote_wakeup(9)
• usb_gadget_set_selfpowered(9)
• usb_gadget_clear_selfpowered(9)
• usb_gadget_vbus_connect(9)
• usb_gadget_vbus_draw(9)
• usb_gadget_vbus_disconnect(9)
• usb_gadget_connect(9)
• usb_gadget_disconnect(9)
• usb_gadget_deactivate(9)
• usb_gadget_activate(9)
• usb_gadget_giveback_request(9)
• gadget_find_ep_by_name(9)
• usb_gadget_check_config(9)
• usb_udc_vbus_handler(9)
• usb_gadget_udc_reset(9)
• usb_gadget_udc_start_locked(9)
• usb_gadget_udc_stop_locked(9)
• usb_gadget_udc_set_speed(9)
• usb_gadget_enable_async_callbacks(9)
• usb_gadget_disable_async_callbacks(9)
• usb_udc_release(9)
• usb_initialize_gadget(9)
• usb_add_gadget(9)
• usb_add_gadget_udc_release(9)
• usb_get_gadget_udc_name(9)
• usb_add_gadget_udc(9)
• usb_del_gadget(9)
• usb_del_gadget_udc(9)

signed off from source/version ./drivers/usb/gadget/udc, dated October 2026, page usb_ep_fifo_status(9) — mwah 💋✨