linux-kernel - Re: [PATCH v6 09/12] usb: gadget: udc: adapt to OTG core

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Date:	Mon, 25 Apr 2016 17:04:07 +0300
From:	Roger Quadros <rogerq@...com>
To:	Jun Li <jun.li@....com>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"balbi@...nel.org" <balbi@...nel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"peter.chen@...escale.com" <peter.chen@...escale.com>
CC:	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"jun.li@...escale.com" <jun.li@...escale.com>,
	"mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>,
	"tony@...mide.com" <tony@...mide.com>,
	"Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
	"abrestic@...omium.org" <abrestic@...omium.org>,
	"r.baldyga@...sung.com" <r.baldyga@...sung.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH v6 09/12] usb: gadget: udc: adapt to OTG core

Hi,

On 21/04/16 09:38, Jun Li wrote:
> Hi,
> 
> ...
>>
>>  /**
>> + * usb_gadget_start - start the usb gadget controller and connect to
>> +bus
>> + * @gadget: the gadget device to start
>> + *
>> + * This is external API for use by OTG core.
>> + *
>> + * Start the usb device controller and connect to bus (enable pull).
>> + */
>> +static int usb_gadget_start(struct usb_gadget *gadget) {
>> +	int ret;
>> +	struct usb_udc *udc = NULL;
>> +
>> +	dev_dbg(&gadget->dev, "%s\n", __func__);
>> +	mutex_lock(&udc_lock);
>> +	list_for_each_entry(udc, &udc_list, list)
>> +		if (udc->gadget == gadget)
>> +			goto found;
>> +
>> +	dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
>> +		__func__);
>> +	mutex_unlock(&udc_lock);
>> +	return -EINVAL;
>> +
>> +found:
>> +	ret = usb_gadget_udc_start(udc);
>> +	if (ret)
>> +		dev_err(&udc->dev, "USB Device Controller didn't start: %d\n",
>> +			ret);
>> +	else
>> +		usb_udc_connect_control(udc);
> 
> For drd, it's fine, but for real otg, gadget connect should be done
> by loc_conn() instead of gadget start.

It is upto the OTG state machine to call gadget_start() when it needs to
connect to the bus (i.e. loc_conn()). I see no point in calling
gadget start before.

Do you see any issue in doing so?

cheers,
-roger

> 
>> +
>> +	mutex_unlock(&udc_lock);
>> +
>> +	return ret;
>> +}
>> +
>> +/**
>> + * usb_gadget_stop - disconnect from bus and stop the usb gadget
>> + * @gadget: The gadget device we want to stop
>> + *
>> + * This is external API for use by OTG core.
>> + *
>> + * Disconnect from the bus (disable pull) and stop the
>> + * gadget controller.
>> + */
>> +static int usb_gadget_stop(struct usb_gadget *gadget) {
>> +	struct usb_udc *udc = NULL;
>> +
>> +	dev_dbg(&gadget->dev, "%s\n", __func__);
>> +	mutex_lock(&udc_lock);
>> +	list_for_each_entry(udc, &udc_list, list)
>> +		if (udc->gadget == gadget)
>> +			goto found;
>> +
>> +	dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
>> +		__func__);
>> +	mutex_unlock(&udc_lock);
>> +	return -EINVAL;
>> +
>> +found:
>> +	usb_gadget_disconnect(udc->gadget);
> 
> Likewise, gadget disconnect also should be done by loc_conn()
> instead of gadget stop.
> 
>> +	udc->driver->disconnect(udc->gadget);
>> +	usb_gadget_udc_stop(udc);
>> +	mutex_unlock(&udc_lock);
>> +
>> +	return 0;
>> +}
>> +
> 
> Li Jun
>