STRUCT USB_OS_STRING(9)

✨ struct usb_os_string(9) ✨

okay so bestie, welcome to the Kernel API Manual — section 9, we're in the gadget weeds today 💅 this one's all about struct usb_os_string, which is literally the thing that represents the OS String that a gadget reports. that's it, that's the vibe 🎀

🌸 SYNOPSIS 🌸

here's the whole struct, character for character, no cap:

struct usb_os_string {
    __u8 bLength;
    __u8 bDescriptorType;
    __u8 qwSignature[OS_STRING_QW_SIGN_LEN];
    __u8 bMS_VendorCode;
    __u8 bPad;
 };

💖 MEMBERS 💖

• bLength — the total length of the entire descriptor, and it's always 0x12. like, always always. don't be quirky about it 🫶
• bDescriptorType — this bad boy is USB_DT_STRING. that's the whole assignment, icon behavior ⭐
• qwSignature — the OS String proper, the main character energy of the whole struct 👑
• bMS_VendorCode — the code the host uses for the requests that come after this one 🔥
• bPad — not used at all, and it must be zero. zero. nada. nothing. don't put stuff in there 🙈

🦋 SEE ALSO 🦋

so many siblings, iykyk 😭 all of these live in the kernel file ./drivers/usb/gadget/composite.c:

• function_descriptors(9)
• next_desc(9)
• config_ep_by_speed_and_alt(9)
• config_ep_by_speed(9)
• usb_add_function(9)
• usb_function_deactivate(9)
• usb_function_activate(9)
• usb_interface_id(9)
• usb_func_wakeup(9)
• bos_desc(9)
• usb_add_config(9)
• usb_string_id(9)
• usb_string_ids_tab(9)
• usb_gstrings_attach(9)
• usb_string_ids_n(9)
• usb_composite_probe(9)
• usb_composite_unregister(9)
• usb_composite_setup_continue(9)

ok that's the whole page bestie, go struct responsibly 🧚💜

source: ./drivers/usb/gadget — dated October 2026 — that's the tea, mwah 💋✨