Re: [PATCH v2] usbcore: Add quirk for 255-bytes initial config read

[Randy Dunlap]

On 6/23/26 9:10 AM, Nikhil Solanke wrote:
> 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_CONFIG_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 <stern@xxxxxxxxxxxxxxxxxxx>
> Suggested-by: Michal Pecio <michal.pecio@xxxxxxxxx>
> Closes: https://lore.kernel.org/linux-usb/CAFgddh+JWdT4LLwMc5qjM8q_pBu-fRo2qADR5ovAKoGHWMQrRw@xxxxxxxxxxxxxx/
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@xxxxxxxxxxxxxxx
> 
> Signed-off-by: Nikhil Solanke <nikhilsolanke5@xxxxxxxxx>
> ---
> Changes in v2:
> - Add Documentation
> - Naming changes
> - Refactored to have a better flow with existing code.
> 
>  .../admin-guide/kernel-parameters.txt         |  9 +++
>  drivers/usb/core/config.c                     | 61 ++++++++++++++-----
>  drivers/usb/core/hub.c                        |  6 +-
>  drivers/usb/core/quirks.c                     |  4 ++
>  include/linux/usb/quirks.h                    |  3 +
>  5 files changed, 67 insertions(+), 16 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 97007f4f69d4..af4bf0ef2c7b 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -8158,6 +8158,15 @@ Kernel parameters
>  				q = USB_QUIRK_FORCE_ONE_CONFIG (Device
>  					claims zero configurations,
>  					forcing to 1);
> +                r = USB_QUIRK_WINDOWS_CONFIG_REQ_SIZE (Device
> +                    fails during initialization when asked for
> +                    9-bytes configuration desciptor request. Ask

		                             descriptor

> +                    for 255-bytes request instead to mirror
> +                    Windows' behavior. This quirk is originally
> +                    meant to fix some quirky gamepads that refuse
> +                    to connect in their XInput mode. But it can also
> +                    potentially fix issues with other USB devices
> +                    that work on Windows but not on Linux)

add ending '.'

For all lines added here, use tabs instead of spaces for indentation.


>  			Example: quirks=0781:5580:bk,0a5c:5834:gij
>  
>  	usbhid.mousepoll=


-- 
~Randy