linux-kernel - Re: [RFC 2/2] usb: gadget: udc: Handle gadget

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Date:   Wed, 22 Mar 2023 10:41:46 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Krishna Kurapati <quic_kriskura@...cinc.com>
Cc:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Sebastian Reichel <sre@...nel.org>,
        Colin Ian King <colin.i.king@...il.com>,
        Jiantao Zhang <water.zhangjiantao@...wei.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_ppratap@...cinc.com, quic_wcheng@...cinc.com,
        quic_jackp@...cinc.com, quic_ugoswami@...cinc.com
Subject: Re: [RFC 2/2] usb: gadget: udc: Handle gadget_connect failure during
 bind operation

On Wed, Mar 22, 2023 at 02:57:40PM +0530, Krishna Kurapati wrote:
> In the event, gadget_connect call (which invokes pullup) fails,
> propagate the error to udc bind operation which inturn sends the
> error to configfs. The userspace can then retry enumeartion if
> it chooses to.
> 
> Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
> ---
>  drivers/usb/gadget/udc/core.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index 23b0629a8774..26bfed5c3a45 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -1051,12 +1051,16 @@ EXPORT_SYMBOL_GPL(usb_gadget_set_state);
>  
>  /* ------------------------------------------------------------------------- */
>  
> -static void usb_udc_connect_control(struct usb_udc *udc)
> +static int usb_udc_connect_control(struct usb_udc *udc)
>  {
> +	int ret;
> +
>  	if (udc->vbus)
> -		usb_gadget_connect(udc->gadget);
> +		ret = usb_gadget_connect(udc->gadget);
>  	else
> -		usb_gadget_disconnect(udc->gadget);
> +		ret = usb_gadget_disconnect(udc->gadget);
> +
> +	return ret;
>  }
>  
>  /**
> @@ -1500,11 +1504,16 @@ static int gadget_bind_driver(struct device *dev)
>  	if (ret)
>  		goto err_start;
>  	usb_gadget_enable_async_callbacks(udc);
> -	usb_udc_connect_control(udc);
> +	ret = usb_udc_connect_control(udc);
> +	if (ret)
> +		goto err_connect_control;
>  
>  	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
>  	return 0;
>  
> + err_connect_control:

At this point you need to copy the code in gadget_unbind_driver().  In 
particular, this should have:

+	usb_gadget_disable_async_callbacks(udc);
+	if (gadget->irq)
+		synchronize_irq(gadget->irq);

Alan Stern

> +	usb_gadget_udc_stop(udc);
> +
>   err_start:
>  	driver->unbind(udc->gadget);
>  
> -- 
> 2.40.0
>