Re: [PATCH] usb: core: new quirk to handle devices with zero configurations

[Alan Stern]

On Thu, Feb 26, 2026 at 05:47:37PM +0800, Jie Deng wrote:
> Some USB devices incorrectly report bNumConfigurations as 0 in their
> device descriptor, which causes the USB core to reject them during
> enumeration.
> logs:
> usb 1-2: device descriptor read/64, error -71
> usb 1-2: no configurations
> usb 1-2: can't read configurations, error -22
> 
> However, these devices actually work correctly when
> treated as having a single configuration.
> 
> Add a new quirk USB_QUIRK_FORCE_ONE_CONFIG to handle such devices.
> When this quirk is set, assume the device has 1 configuration instead
> of failing with -EINVAL.
> 
> This quirk is applied to the device with VID:PID 5131:2007 which
> exhibits this behavior.
> 
> Signed-off-by: Jie Deng <dengjie03@xxxxxxxxxx>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 3 +++
>  drivers/usb/core/config.c                       | 7 ++++++-
>  drivers/usb/core/quirks.c                       | 5 +++++
>  include/linux/usb/quirks.h                      | 3 +++
>  4 files changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index cb850e5290c2..63e6d3ebbd7a 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -8183,6 +8183,9 @@ Kernel parameters
>  				p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT
>  					(Reduce timeout of the SET_ADDRESS
>  					request from 5000 ms to 500 ms);
> +				r = USB_QUIRK_FORCE_ONE_CONFIG (Device
> +					claims zero configurations,
> +					forcing to 1);
>  			Example: quirks=0781:5580:bk,0a5c:5834:gij
>  
>  	usbhid.mousepoll=
> diff --git a/drivers/usb/core/config.c b/drivers/usb/core/config.c
> index 1cd5fa61dc76..f60fed224cbb 100644
> --- a/drivers/usb/core/config.c
> +++ b/drivers/usb/core/config.c
> @@ -927,7 +927,12 @@ int usb_get_configuration(struct usb_device *dev)
>  		dev->descriptor.bNumConfigurations = ncfg = USB_MAXCONFIG;
>  	}
>  
> -	if (ncfg < 1) {
> +	if (dev->quirks & USB_QUIRK_FORCE_ONE_CONFIG) {
> +		dev_info(ddev, "Device claims zero configurations,
> +				forcing to 1\n");
> +		dev->descriptor.bNumConfigurations = 1;
> +		ncfg = 1;

What if a device claims to have 2 configurations but the flag is set?  
This will cause the kernel to ignore the second configuration.

> +	} esle if (ncfg < 1) {
-----------^^

Clearly you never compiled this code.

Alan Stern