Re: [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection

From: Chanwoo Choi <cw00.choi@samsung.com>
To: Peter Chen <peter.chen@freescale.com>
Cc: "Ivan T. Ivanov" <iivanov@mm-sol.com>,
	"Balbi, Felipe" <balbi@ti.com>,
	"ABRAHAM, KISHON VIJAY" <kishon@ti.com>,
	Roger Quadros <rogerq@ti.com>,
	Robert Baldyga <r.baldyga@samsung.com>,
	myungjoo.ham@samsung.com, linux-usb@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	m.szyprowski@samsung.com
Subject: Re: [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection
Date: Thu, 16 Apr 2015 17:26:50 +0900	[thread overview]
Message-ID: <552F724A.1050500@samsung.com> (raw)
In-Reply-To: <20150416080107.GC1709@shlinux2>

On 04/16/2015 05:01 PM, Peter Chen wrote:
> On Thu, Apr 16, 2015 at 04:59:31PM +0900, Chanwoo Choi wrote:
>> On 04/16/2015 04:13 PM, Ivan T. Ivanov wrote:
>>> Hi,
>>>
>>> On Thu, 2015-04-16 at 16:00 +0900, Chanwoo Choi wrote:
>>>> Hi Peter,
>>>>
>>>> On 04/16/2015 10:59 AM, Peter Chen wrote:
>>>>>
>>>
>>>>> Ok, from USB point, external id/vbus value can't decide
>>>>> which role the controller will be, the controller driver
>>>>> will decide role according to many things, eg, user configurations,
>>>>> id/vbus value, OTG HNP, etc.
>>>>>
>>>>> So, from USB controller/phy driver, it doesn't care which cable is
>>>>> inserted, it cares about id/vbus value. Eg, it can get id/vbus value
>>>>> and it will be notified when the id/vbus value has changed.
>>>>
>>>> OK, I change the notifier name and add notifier events as following:
>>>>
>>>> - extcon_{register|unregister}_usb_notifier(struct extcon_dev *edev, struct notifier_block *nb);
>>>> - list of notifier events
>>>>         #define EXTCON_USB_ID_L_VBUS_L0       /* ID low  and VBUS low */
>>>>         #define EXTCON_USB_ID_L_VBUS_H1       /* ID low  and VBUS high */
>>>>         #define EXTCON_USB_ID_H_VBUS_L2       /* ID high and VBUS low */
>>>>         #define EXTCON_USB_ID_H_VBUS_H3       /* ID high and VBUS high */
>>>
>>> I am still confused, why we mix ID and VBUS events into one? 
>>> Those are two lines and they are not necessarily handled by
>>> the same extcon_dev.
>>
>> IMO, if some usb driver check both id and vbus pin at the same time,
>> the usb driver can know the both id and vbus pin state through only one notifier event.
>>
>> Also,
>> If some usb driver want to know the state of id pin except of vbus state,
>> when receiving following events, id pin is low.
>> 	#define EXTCON_USB_ID_L_VBUS_L0
>> 	#define EXTCON_USB_ID_L_VBUS_H1
>> when receiving following events, id pin is high.
>> 	#define EXTCON_USB_ID_H_VBUS_L2
>> 	#define EXTCON_USB_ID_H_VBUS_H3
>> Also, some usb driver would catch the vbus pin state with same method.
>>
>> But, it is just my opinion. We may use following notifier events for each pin.
>> We need to discuss it.
>> 	#define EXTCON_USB_ID_LOW
>> 	#define EXTCON_USB_ID_HIGH	
>> 	#define EXTCON_USB_VBUS_LOW
>> 	#define EXTCON_USB_VBUS_HIGH
>> 	
> 
> I agree with above definition.
> 

OK. I understand.