STRUCT USB_DFU_FUNCTIONAL_DESCRIPTOR(9)

✨ NAME ✨

struct usb_dfu_functional_descriptor — the DFU Functional descriptor, bestie 💖 (this is from the Kernel API Manual, in case you were wondering 🫶)

🌸 SYNOPSIS 🌸

struct usb_dfu_functional_descriptor {
    __u8 bLength;
    __u8 bDescriptorType;
    __u8 bmAttributes;
    __le16 wDetachTimeOut;
    __le16 wTransferSize;
    __le16 bcdDFUVersion;
 };

okay so that's the whole shape of it — six fields, no cap, and every single one of them matters 💅

🎀 Members 🎀

• bLength — how big the descriptor is, in bytes. it's giving "measure twice" energy 📏
• bDescriptorType — it's USB_DT_DFU_FUNCTIONAL. that's the type tag, periodt ✨
• bmAttributes — the DFU attributes. the whole vibe of the thing, basically 🦋
• wDetachTimeOut — the maximum time you wait after DFU_DETACH, and it's in ms, stored as an le16 ⏳ (yes bestie, little-endian, don't forget 🙈)
• wTransferSize — the maximum number of bytes per control-write, also an le16. know your limits, queen 👑
• bcdDFUVersion — the DFU Spec version in BCD, again le16. version queen behaviour 🌈

ngl the le16 thing is not a suggestion — those three fields are little-endian in the struct, fr fr 💀

🦋 SEE ALSO 🦋

• Kernel file ./include/uapi/linux/usb/functionfs.h
• struct usb_ffs_dmabuf_transfer_req(9)
• descriptors(9)

and that's the whole page, bestie 🥰 this lil' icon lives in ./include/uapi/linux/usb, dated October 2026, and it's all struct usb_d...l_descriptor(9) at the end of the day 💜 stay slay, stay little-endian ✨🎀