usb_ep_set_halt(9)

📦 version 7.3.1, in nixpkgs unstable

🎀 usb_ep_set_halt 💅

okay so bestie, welcome to the Kernel API Manual — this one's a kernel function page and it's literally about hitting the stall button on a USB endpoint. sit down, hydrate, let's go ✨

🌸 NAME 🌸

usb_ep_set_halt — sets the endpoint halt feature. that's it, that's the whole vibe. it stalls an endpoint. periodt 🫶

✨ SYNOPSIS ✨

int usb_ep_set_halt (struct usb_ep *ep );

one function, one struct pointer, one int coming back at you. iconic minimalism ngl 💜

🦋 ARGUMENTS 🦋

  • ep — the non-isochronous endpoint being stalled. read that again: non-isochronous. iso endpoints are not invited to this party 🙈

💖 DESCRIPTION 💖

Use this to stall an endpoint, maybe as a way of reporting an error. lowkey it's the "girl, no" of USB transfers 😭

Except for control endpoints, the endpoint stays halted — meaning it will not stream any data — until the host clears this feature. so it's not a little pause, it's a full-on "we're closed" sign. drivers may need to empty the endpoint's request queue first, to make sure no inappropriate transfers happen. yes, literally clean out the queue first, no cap 🧹

💀 heads up: a CLEAR_FEATURE on an endpoint will be invisible to the gadget driver, but a SET_INTERFACE will not be. that asymmetry is real and it Will get you.

To reset endpoints for the current altsetting, see usb_ep_clear_halt. When you're switching altsettings, it's simplest to use usb_ep_enable or usb_ep_disable for the endpoints. like, just use the right tool bestie 🎀

This routine may be called in interrupt context. yes, interrupt context. she's flexible like that ✨

Returns zero, or a negative error code. On success, this call sets underlying hardware state that blocks data transfers — so the hardware itself is doing the blocking, not just vibes 🔥

Attempts to halt IN endpoints will fail (returning -EAGAIN) if any transfer requests are still queued, or if the controller hardware (usually a FIFO) still holds bytes that the host hasn't collected. so: drain your queue, and make sure the FIFO isn't still sitting on data the host ghosted 👻 -EAGAIN is the "try again" of it all, and honestly? relatable.

🌈 SEE ALSO 🌈

the whole friend group, fr fr:

like, the entire UDC extended universe. iykyk 🧚

🍓 and that's the page!! this lil beauty ships from the source ./drivers/usb/gadget/udc, dated October 2026 — go forth and stall responsibly, bestie. mwah 💋👑
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