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

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Date:	Mon, 16 May 2016 17:23:23 +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 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.

> > 
> >>  	return 0;
> >> @@ -660,9 +830,15 @@ static ssize_t usb_udc_softconn_store(struct device *dev,
> >>  		return -EOPNOTSUPP;
> >>  	}
> >>  
> >> +	/* In OTG mode we don't support softconnect, but b_bus_req */
> >> +	if (udc->gadget->otg_dev) {
> >> +		dev_err(dev, "soft-connect not supported in OTG mode\n");
> >> +		return -EOPNOTSUPP;
> >> +	}
> >> +
> > 
> > The soft-connect can be supported at dual-role mode currently, we can
> > use b_bus_req entry once it is implemented later.
> 
> Soft-connect should be done via sysfs handling within the OTG core.
> This can be added later. I don't want anything outside the OTG core
> to handle soft-connect behaviour as it will be hard to keep things
> in sync.
> 
> I can update the comment to something like this.
> 
> /* In OTG/dual-role mode, soft-connect should be handled by OTG core */

Ok, let's Felipe decide it.

> 
> > 
> >>  	if (sysfs_streq(buf, "connect")) {
> >>  		usb_gadget_udc_start(udc);
> >> -		usb_gadget_connect(udc->gadget);
> >> +		usb_udc_connect_control(udc);
> > 
> > This line seems to be not related with this patch.
> > 
> Right. I'll remove it.
> 
> cheers,
> -roger

-- 

Best Regards,
Peter Chen