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

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Message-ID: <20150416080107.GC1709@shlinux2>
Date:	Thu, 16 Apr 2015 16:01:08 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	Chanwoo Choi <cw00.choi@...sung.com>
CC:	"Ivan T. Ivanov" <iivanov@...sol.com>,
	"Balbi, Felipe" <balbi@...com>,
	"ABRAHAM, KISHON VIJAY" <kishon@...com>,
	Roger Quadros <rogerq@...com>,
	Robert Baldyga <r.baldyga@...sung.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 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.

-- 

Best Regards,
Peter Chen
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