linux-kernel - Re: [PATCH v5] usb: gadget: udc: Handle gadget

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Date:   Wed, 27 Sep 2023 09:38:57 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Krishna Kurapati <quic_kriskura@...cinc.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Francesco Dolcini <francesco.dolcini@...adex.com>,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        Ivan Orlov <ivan.orlov0322@...il.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_ppratap@...cinc.com, quic_wcheng@...cinc.com,
        quic_jackp@...cinc.com
Subject: Re: [PATCH v5] usb: gadget: udc: Handle gadget_connect failure
 during bind operation

On Wed, Sep 27, 2023 at 01:00:27PM +0530, Krishna Kurapati wrote:
> In the event gadget_connect call (which invokes pullup) fails,
> propagate the error to udc bind operation which in turn sends the
> error to configfs. The userspace can then retry enumeration if
> it chooses to.
> 
> Signed-off-by: Krishna Kurapati <quic_kriskura@...cinc.com>
> ---
> Changes in v5: Addressed proper unlocking of control_lock mutex

Reviewed-by: Alan Stern <stern@...land.harvard.edu>

>  drivers/usb/gadget/udc/core.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index 7d49d8a0b00c..824fe64e078a 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -1125,12 +1125,12 @@ EXPORT_SYMBOL_GPL(usb_gadget_set_state);
>  /* ------------------------------------------------------------------------- */
>  
>  /* Acquire connect_lock before calling this function. */
> -static void usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc->connect_lock)
> +static int usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc->connect_lock)
>  {
>  	if (udc->vbus)
> -		usb_gadget_connect_locked(udc->gadget);
> +		return usb_gadget_connect_locked(udc->gadget);
>  	else
> -		usb_gadget_disconnect_locked(udc->gadget);
> +		return usb_gadget_disconnect_locked(udc->gadget);
>  }
>  
>  static void vbus_event_work(struct work_struct *work)
> @@ -1604,12 +1604,23 @@ static int gadget_bind_driver(struct device *dev)
>  	}
>  	usb_gadget_enable_async_callbacks(udc);
>  	udc->allow_connect = true;
> -	usb_udc_connect_control_locked(udc);
> +	ret = usb_udc_connect_control_locked(udc);
> +	if (ret)
> +		goto err_connect_control;
> +
>  	mutex_unlock(&udc->connect_lock);
>  
>  	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
>  	return 0;
>  
> + err_connect_control:
> +	udc->allow_connect = false;
> +	usb_gadget_disable_async_callbacks(udc);
> +	if (gadget->irq)
> +		synchronize_irq(gadget->irq);
> +	usb_gadget_udc_stop_locked(udc);
> +	mutex_unlock(&udc->connect_lock);
> +
>   err_start:
>  	driver->unbind(udc->gadget);
>  
> -- 
> 2.42.0
>