Re: [PATCH v4] usb: gadget: udc: Handle gadget_connect failure during bind operation

[Krishna Kurapati PSSNV]

On 9/27/2023 1:24 AM, Alan Stern wrote:
> On Wed, Sep 27, 2023 at 01:07:08AM +0530, Krishna Kurapati wrote:
> > In the event, gadget_connect call (which invokes pullup) fails,
>
> s/event,/event/
>
> > propagate the error to udc bind operation which inturn sends the
>
> s/inturn/in turn/
>
> > error to configfs. The userspace can then retry enumeartion if
>
> s/enumeartion/enumeration/
>
> > it chooses to.
> >
> > Signed-off-by: Krishna Kurapati <quic_kriskura@xxxxxxxxxxx>
> > ---
> > Changes in v4: Fixed mutex locking imbalance during connect_control
> > failure
> > Link to v3: https://lore.kernel.org/all/20230510075252.31023-3-quic_kriskura@xxxxxxxxxxx/
> >
> >   drivers/usb/gadget/udc/core.c | 23 +++++++++++++++++++----
> >   1 file changed, 19 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> > index 7d49d8a0b00c..53af25a333a1 100644
> > --- a/drivers/usb/gadget/udc/core.c
> > +++ b/drivers/usb/gadget/udc/core.c
> > @@ -1125,12 +1125,16 @@ 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)
> >   {
> > +	int ret;
> > +
> >   	if (udc->vbus)
> > -		usb_gadget_connect_locked(udc->gadget);
> > +		ret = usb_gadget_connect_locked(udc->gadget);
> >   	else
> > -		usb_gadget_disconnect_locked(udc->gadget);
> > +		ret = usb_gadget_disconnect_locked(udc->gadget);
> > +
> > +	return ret;
>
> You don't actually need the new variable ret.  You can just do:
>
> 	if (udc->vbus)
> 		return usb_gadget_connect_locked(udc->gadget);
> 	else
> 		return usb_gadget_disconnect_locked(udc->gadget);
>
> >   }
> >   
> >   static void vbus_event_work(struct work_struct *work)
> > @@ -1604,12 +1608,23 @@ 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) {
> > +		mutex_unlock(&udc->connect_lock);
> > +		goto err_connect_control;
> > +	}
> > +
> >   	mutex_unlock(&udc->connect_lock);
> >   
> >   	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
> >   	return 0;
> >   
> > + err_connect_control:
> > +	usb_gadget_disable_async_callbacks(udc);
> > +	if (gadget->irq)
> > +		synchronize_irq(gadget->irq);
> > +	usb_gadget_udc_stop_locked(udc);
>
> Not good -- usb_gadget_udc_stop_locked() expects you to be holding
> udc->connect_lock, but you just dropped the lock!  Also, you never set
> udc->allow_connect back to false.
>
> You should move the mutex_unlock() call from inside the "if" statement
> to down here, and add a line for udc->allow_connect.

Hi Alan,

 Thanks for the review. Will push v5 addressing the changes.


Regards,
Krishna,