linux-kernel - Re: [PATCH v10 13/14] usb: gadget: udc: adapt to OTG core

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Message-ID: <575E62D7.8010409@ti.com>
Date:	Mon, 13 Jun 2016 10:37:59 +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>,
	<joe@...ches.com>, <linux-usb@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<devicetree@...r.kernel.org>
Subject: Re: [PATCH v10 13/14] usb: gadget: udc: adapt to OTG core

On 13/06/16 10:20, Peter Chen wrote:
> On Mon, Jun 13, 2016 at 10:14:31AM +0300, Roger Quadros wrote:
>> On 12/06/16 14:36, Peter Chen wrote:
>>> On Fri, Jun 10, 2016 at 04:07:22PM +0300, Roger Quadros wrote:
>>>>  
>>>> +/**
>>>> + * usb_otg_add_gadget_udc - adds a new gadget to the udc class driver list
>>>> + * @parent: the parent device to this udc. Usually the controller
>>>> + * driver's device.
>>>
>>> It seems it should be udc device
>>
>> Parent and udc->dev are not the same right?
> 
> Sure, udc's parent is otg device.
> 
>>
>> I guess i'll omit the second statement to avoid confusion. So.
>>
>> @parent: the parent device to this udc.
> 
> Where you call below APIs? It seems to be a udc driver, right?
> So, when you try to get "otg-controller" from the node, this node
> should be udc.

@parent is actually the device that represents the USB Device controller
in the device tree. When you call usb_add_gadget_udc_release() a new
udc->dev device is created as it's child.

See explanation for the @parent argument in usb_add_gadget_udc_release().
As we want to keep the parent argument identical to that I will not make
any changes then.

> 
> /**
>  * usb_otg_add_gadget_udc - adds a new gadget to the udc class driver list
>  * @parent: the parent device to this udc. Usually the controller
>  * driver's device.
>  * @gadget: the gadget to be added to the list
>  * @otg_dev: the OTG controller device
>  *
>  * If otg_dev is NULL then device tree node is checked
>  * for OTG controller via the otg-controller property.
>  * Returns zero on success, negative errno otherwise.
>  */
> int usb_otg_add_gadget_udc(struct device *parent, struct usb_gadget *gadget,
> 			   struct device *otg_dev)
> {
> 	if (!otg_dev) {
> 		gadget->otg_dev = of_usb_get_otg(parent->of_node);
> 		if (!gadget->otg_dev)
> 			return -ENODEV;
> 	} else {
> 		gadget->otg_dev = otg_dev;
> 	}
> 
> 	return usb_add_gadget_udc_release(parent, gadget, NULL);
> }
> EXPORT_SYMBOL_GPL(usb_otg_add_gadget_udc);
> 

--
cheers,
-roger