Re: [PATCH 1/3] usb: gadget: f_acm: Claim requested USB endpoints

[Mattijs Korpershoek <mkorpershoek@kernel.org>]

Hi Stephan,

Thank you for the patch.

On lun., avril 07, 2025 at 16:59, Stephan Gerhold <stephan.gerhold@linaro.org> wrote:

> U-Boot has an older version of the Linux gadget API, where USB endpoints
> returned by usb_ep_autoconfig() are not automatically claimed. As written
> in the documentation comment:
>
>  "To prevent the endpoint from being returned by a later autoconfig call,
>   claim it by assigning ep->driver_data to some non-null value."
>
> Right now f_acm doesn't do that, which means that e.g. ep_in and ep_notify
> may end up being assigned the same endpoint. Surprisingly, the ACM console
> is still somehow working, but this is not the expected behavior. It will
> break with a later commit that disallows calling usb_ep_enable() multiple
> times.
>
> Fix this by assigning some data to ep->driver_data, similar to the other
> gadget drivers.
>
> Fixes: fc2b399ac03b ("usb: gadget: Add CDC ACM function")
> Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>

Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>

> ---
>  drivers/usb/gadget/f_acm.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/usb/gadget/f_acm.c b/drivers/usb/gadget/f_acm.c
> index f18c6a0a76110df62e925de1882316eed463b343..2665fa4168f99b35a8c595aa24cb3fc4e8ab8529 100644
> --- a/drivers/usb/gadget/f_acm.c
> +++ b/drivers/usb/gadget/f_acm.c
> @@ -238,18 +238,21 @@ static int acm_bind(struct usb_configuration *c, struct usb_function *f)
>  		return -ENODEV;
>  
>  	f_acm->ep_in = ep;
> +	ep->driver_data = c->cdev; /* claim */
>  
>  	ep = usb_ep_autoconfig(gadget, &acm_fs_out_desc);
>  	if (!ep)
>  		return -ENODEV;
>  
>  	f_acm->ep_out = ep;
> +	ep->driver_data = c->cdev; /* claim */
>  
>  	ep = usb_ep_autoconfig(gadget, &acm_fs_notify_desc);
>  	if (!ep)
>  		return -ENODEV;
>  
>  	f_acm->ep_notify = ep;
> +	ep->driver_data = c->cdev; /* claim */
>  
>  	if (gadget_is_dualspeed(gadget)) {
>  		/* Assume endpoint addresses are the same for both speeds */
>
> -- 
> 2.47.2