linux-kernel - Re: [PATCH v8 13/14] usb: gadget: udc: adapt to OTG core

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Date:	Wed, 18 May 2016 11:18:30 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Roger Quadros <rogerq@...com>
Cc:	peter.chen@...escale.com, balbi@...nel.org, tony@...mide.com,
	gregkh@...uxfoundation.org, dan.j.williams@...el.com,
	mathias.nyman@...ux.intel.com, Joao.Pinto@...opsys.com,
	sergei.shtylyov@...entembedded.com, jun.li@...escale.com,
	grygorii.strashko@...com, yoshihiro.shimoda.uh@...esas.com,
	robh@...nel.org, nsekhar@...com, b-liu@...com,
	linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v8 13/14] usb: gadget: udc: adapt to OTG core

On Mon, May 16, 2016 at 12:51:53PM +0300, Roger Quadros wrote:
> On 16/05/16 12:23, Peter Chen wrote:
> > On Mon, May 16, 2016 at 11:26:57AM +0300, Roger Quadros wrote:
> >> Hi,
> >>
> >> On 16/05/16 10:02, Peter Chen wrote:
> >>> On Fri, May 13, 2016 at 01:03:27PM +0300, Roger Quadros wrote:
> >>>> +
> >>>> +static int usb_gadget_connect_control(struct usb_gadget *gadget, bool connect)
> >>>> +{
> >>>> +	struct usb_udc *udc;
> >>>> +
> >>>> +	mutex_lock(&udc_lock);
> >>>> +	udc = usb_gadget_to_udc(gadget);
> >>>> +	if (!udc) {
> >>>> +		dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
> >>>> +			__func__);
> >>>> +		mutex_unlock(&udc_lock);
> >>>> +		return -EINVAL;
> >>>> +	}
> >>>> +
> >>>> +	if (connect) {
> >>>> +		if (!gadget->connected)
> >>>> +			usb_gadget_connect(udc->gadget);
> >>>> +	} else {
> >>>> +		if (gadget->connected) {
> >>>> +			usb_gadget_disconnect(udc->gadget);
> >>>> +			udc->driver->disconnect(udc->gadget);
> >>>> +		}
> >>>> +	}
> >>>> +
> >>>> +	mutex_unlock(&udc_lock);
> >>>> +
> >>>> +	return 0;
> >>>> +}
> >>>> +
> >>>
> >>> Since this is called for vbus interrupt, why not using
> >>> usb_udc_vbus_handler directly, and call udc->driver->disconnect
> >>> at usb_gadget_stop.
> >>
> >> We can't assume that this is always called for vbus interrupt so
> >> I decided not to call usb_udc_vbus_handler.
> >>
> >> udc->vbus is really pointless for us. We keep vbus states in our
> >> state machine and leave udc->vbus as ture always.
> >>
> >> Why do you want to move udc->driver->disconnect() to stop?
> >> If USB controller disconnected from bus then the gadget driver
> >> must be notified about the disconnect immediately. The controller
> >> may or may not be stopped by the core.
> >>
> > 
> > Then, would you give some comments when this API will be used?
> > I was assumed it is only used for drd state machine.
> 
> drd_state machine didn't even need this API in the first place :).
> You guys wanted me to separate out start/stop and connect/disconnect for full OTG case.
> Won't full OTG state machine want to use this API? If not what would it use?
> 

Oh, I meant only drd and fully otg state machine needs it. I am
wondering if we need have a new API to do it. Two questions:

- Except for vbus interrupt, any chances this API will be used at
current logic?
- When this API is called but without a coming gadget->stop?

-- 

Best Regards,
Peter Chen