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

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Date:	Wed, 18 May 2016 15:45:11 +0300
From:	Roger Quadros <rogerq@...com>
To:	Peter Chen <hzpeterchen@...il.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 18/05/16 06:18, Peter Chen wrote:
> 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:

OK.
> 
> - Except for vbus interrupt, any chances this API will be used at
> current logic?

I don't think so. But we can't assume caller behaviour for any API.

> - When this API is called but without a coming gadget->stop?
> 
Never for DRD case. But we want to catch wrong users.

cheers,
-roger