Re: [PATCH 1/1] usb: gadget: call usb_gadget_check_config() to verify UDC capability

[Ravi Gunasekaran]

On 6/29/23 3:54 AM, Frank Li wrote:
> The legacy gadget driver omitted calling usb_gadget_check_config()
> to ensure that the USB device controller (UDC) has adequate resources,
> including sufficient endpoint numbers and types, to support the given
> configuration.
> 
> Previously, usb_add_config() was solely invoked by the legacy gadget
> driver. Adds the necessary usb_gadget_check_config() after the bind()
> operation to fix the issue.
> 
> Fixes: dce49449e04f ("usb: cdns3: allocate TX FIFO size according to composite EP number")
> Reported-by: Ravi Gunasekaran <r-gunasekaran@xxxxxx>
> Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> ---
>  drivers/usb/gadget/composite.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index 1b3489149e5e..dd9b90481b4c 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -1125,6 +1125,10 @@ int usb_add_config(struct usb_composite_dev *cdev,
>  		goto done;
>  
>  	status = bind(config);
> +
> +	if (status == 0)
> +		status = usb_gadget_check_config(cdev->gadget);

This will work for legacy gadgets that support only one configurations.
Take for example g_ether. It has two configurations when RNDIS is enabled.
And usb_add_config() is invoked for each configuration. 

cdns3_gadget_check_config() calculates the total IN end-points based on the
ep->claimed flag. 

        list_for_each_entry(ep, &gadget->ep_list, ep_list) {                
                if (ep->claimed && (ep->address & USB_DIR_IN))              
                        n_in++;                                             
        }  

This ep->claimed flag is later cleared by usb_ep_autoconfig_reset() which is
invoked in usb_add_config(). So for multi-configurations, actual total in end points
is not taken into consideration thus resulting in incorrect fifo size allocation/check.

g_ffs is another gadget which has multiple configurations.


> +
>  	if (status < 0) {
>  		while (!list_empty(&config->functions)) {
>  			struct usb_function		*f;

-- 
Regards,
Ravi