STRUCT USB_CTRLREQUEST(9)

💅 struct usb_ctrlrequest(9) — like, the manual page bestie

okay so this is a page from the Kernel API Manual and honestly? it's a little guy with a big job. it's struct usb_ctrlrequest, and no cap it's the main character of USB control requests. let's get into it 🎀

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✨ NAME ✨

struct usb_ctrlrequest — the SETUP data for a USB device control request. that's it, that's the vibe 🦋

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🌸 SYNOPSIS 🌸

struct usb_ctrlrequest {
    __u8 bRequestType;
    __u8 bRequest;
    __le16 wValue;
    __le16 wIndex;
    __le16 wLength;
 };

five fields, zero notes, absolute icon behavior ✨

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🫶 Members 🫶

here's the whole cast, one by one:

• bRequestType — matches the USB bmRequestType field. yeah that's the name, don't come for me 💀
• bRequest — matches the USB bRequest field. consistent queen 💅
• wValue — matches the USB wValue field. it's in le16 byte order, fyi 👀
• wIndex — matches the USB wIndex field. also le16 byte order, keep up bestie 🍓
• wLength — matches the USB wLength field. yep, le16 byte order again 🌸

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🔥 Description 🔥

so this struct is what you use to send control requests to a USB device. it lines up exactly with the different fields of the USB 2.0 Spec section 9.3, table 9-2. if you want the fuller lore on what each field actually does, go read the USB spec — it's giving required reading ngl 📚

⚠️ important lil note: the driver for any interface can issue control requests. for most devices, interfaces don't coordinate with each other, so those requests can be made at any time. literally whenever. no scheduling, no meetings, no heads up 😭

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👑 SEE ALSO 👑

all the siblings and cousins, gathered here for your convenience:

• Kernel file ./include/uapi/linux/usb/ch9.h
• usb_endpoint_num(9)
• usb_endpoint_type(9)
• usb_endpoint_dir_in(9)
• usb_endpoint_dir_out(9)
• usb_endpoint_xfer_bulk(9)
• usb_endpoint_xfer_control(9)
• usb_endpoint_xfer_int(9)
• usb_endpoint_xfer_isoc(9)
• usb_endpoint_is_bulk_in(9)
• usb_endpoint_is_bulk_out(9)
• usb_endpoint_is_int_in(9)
• usb_endpoint_is_int_out(9)
• usb_endpoint_is_isoc_in(9)
• usb_endpoint_is_isoc_out(9)
• usb_endpoint_maxp(9)
• usb_endpoint_maxp_mult(9)

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and that's the whole page, bestie 💜 it lives at ./include/uapi/linux/usb and this version is dated October 2026 — slay, go forth and send your control requests responsibly 🧚✨