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

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Date:	Thu, 30 Apr 2015 16:55:22 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Roger Quadros <rogerq@...com>
Cc:	Peter Chen <peter.chen@...escale.com>,
	Robert Baldyga <r.baldyga@...sung.com>,
	"Ivan T. Ivanov" <iivanov@...sol.com>,
	"Balbi, Felipe" <balbi@...com>,
	"ABRAHAM, KISHON VIJAY" <kishon@...com>, myungjoo.ham@...sung.com,
	linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, m.szyprowski@...sung.com
Subject: Re: [PATCH v3 2/4] extcon: usb-gpio: add support for VBUS detection

On 04/30/2015 04:32 PM, Roger Quadros wrote:
> On 16/04/15 11:26, Chanwoo Choi wrote:
>> 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.
>>
>>
> Chanwoo, Robert,
> 

Hi Roger,

> Do we have an agreement on a common solution then?

Yes.

> IMO the above mentioned 4 notifier events should meet all our USB needs.

I'll support usb notifier chain which includes 4 notifier events.

Thanks,
Chanwoo Choi


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