Re: [PATCH 1/3] usbcore: Add quirk for 255-bytes initial config read

On Sun, Jul 26, 2026 at 06:50:38PM +0530, Ishaan Dandekar wrote:
> From: Nikhil Solanke <[email protected]>
> 
> Certain third-party USB game controllers exposing (or spoofing) an Xbox
> 360-compatible interface (VID:PID 045e:028e) fail to enumerate under Linux.
> The device disconnects from the bus without responding to the initial
> GET_DESCRIPTOR(CONFIGURATION) request, and the kernel logs 'unable to read
> config index 0 descriptor/start: -71'.
> 
> The device then falls back to a secondary Android HID mode (with a
> different VID:PID), losing XInput functionality including rumble support.
> The failure reproduces across multiple machines, host controller types, and
> kernel versions including current mainline and LTS. The device enumerates
> correctly and remains in XInput mode under Windows. Notably, the device
> enumerates correctly in Android mode when the same 9-byte request
> is issued for that mode's configuration descriptor, confirming the firmware
> bug is specific to the XInput mode.
> 
> usbmon traces from Linux and Wireshark/USBPcap traces from Windows are
> identical up to the point of failure, with no visible protocol-level
> difference explaining the divergence. The root cause was identified when
> Michal Pecio discovered via a QEMU bus-level capture that Windows does not
> use wLength=9 for the initial config descriptor request; it uses
> wLength=255. Alan Stern subsequently confirmed this with a bus
> analyzer on a different USB 2.0 device, and Michal verified the behavior
> goes back to Windows 95 OSR2.1.
> 
> So, add a new quirk flag USB_QUIRK_WINDOWS_CONFIG_REQ_SIZE which causes
> usb_get_configuration() to issue a 255 byte sized configuration request
> instead of USB_DT_CONFIG_SIZE (9) for the initial
> GET_DESCRIPTOR(CONFIGURATION) request, mimicking long-standing Windows
> behavior.
> 
> Suggested-by: Alan Stern <[email protected]>
> Suggested-by: Michal Pecio <[email protected]>
> Closes: https://lore.kernel.org/linux-usb/CAFgddh+JWdT4LLwMc5qjM8q_pBu-fRo2qADR5ovAKoGHWMQrRw@mail.gmail.com/
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: [email protected]
> Signed-off-by: Nikhil Solanke <[email protected]>
> ---
>  .../admin-guide/kernel-parameters.txt         | 10 +++++
>  drivers/usb/core/config.c                     | 39 +++++++++++++++----
>  drivers/usb/core/quirks.c                     |  4 ++
>  include/linux/usb/quirks.h                    |  3 ++
>  4 files changed, 49 insertions(+), 7 deletions(-)

Cool, but you can't send on someone else's patch without also signing
off on it :)

thanks,

greg k-h