linux-kernel - Re: [PATCH v2] usb: dwc3: gadget: Reset num TRBs before giving back the request

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Date:   Thu, 1 Jun 2023 22:19:11 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Elson Roy Serrao <quic_eserrao@...cinc.com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "quic_wcheng@...cinc.com" <quic_wcheng@...cinc.com>,
        "quic_jackp@...cinc.com" <quic_jackp@...cinc.com>
Subject: Re: [PATCH v2] usb: dwc3: gadget: Reset num TRBs before giving back
 the request

On Thu, Jun 01, 2023, Elson Roy Serrao wrote:
> Consider a scenario where cable disconnect happens when there is an active
> usb reqest queued to the UDC. As part of the disconnect we would issue an
> end transfer with no interrupt-on-completion before giving back this
> request. Since we are giving back the request without skipping TRBs the
> num_trbs field of dwc3_request still holds the stale value previously used.
> Function drivers re-use same request for a given bind-unbind session and
> hence their dwc3_request context gets preserved across cable
> disconnect/connect. When such a request gets re-queued after cable connect,
> we would increase the num_trbs field on top of the previous stale value
> thus incorrectly representing the number of TRBs used. Fix this by
> resetting num_trbs field before giving back the request.
> 
> Fixes: 09fe1f8d7e2f ("usb: dwc3: gadget: track number of TRBs per request")
> Signed-off-by: Elson Roy Serrao <quic_eserrao@...cinc.com>
> ---
> Changes in v2:
>  - Addressed Thinh's comment to reset num_trbs in dwc3_gadget_del_and_unmap_request
>    rather than calling skip_trbs.
>  - Modify the commit message to match the modification.
> 
>  drivers/usb/dwc3/gadget.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 578804d..0ded919 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -198,6 +198,7 @@ static void dwc3_gadget_del_and_unmap_request(struct dwc3_ep *dep,
>  	list_del(&req->list);
>  	req->remaining = 0;
>  	req->needs_extra_trb = false;
> +	req->num_trbs = 0;
>  
>  	if (req->request.status == -EINPROGRESS)
>  		req->request.status = status;
> -- 
> 2.7.4
> 

Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>

Thanks,
Thinh