linux-kernel - Re: [PATCH v4] extcon: gpio: Add the support for Device tree bindings

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Date:	Tue, 31 May 2016 15:44:39 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Rob Herring <robh@...nel.org>,
	Venkat Reddy Talla <vreddytalla@...dia.com>
Cc:	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	devicetree@...r.kernel.org, Kumar Gala <galak@...eaurora.org>,
	linux-kernel@...r.kernel.org,
	Laxman Dewangan <ldewangan@...dia.com>
Subject: Re: [PATCH v4] extcon: gpio: Add the support for Device tree bindings

On 2016년 05월 28일 00:29, Rob Herring wrote:
> On Thu, May 26, 2016 at 05:17:45PM +0530, Venkat Reddy Talla wrote:
>> Add the support for Device tree bindings of extcon-gpio driver.
>> The extcon-gpio device tree node must include the both 'extcon-id' and
>> 'gpios' property.
> 
> I think extcon bindings are a mess in general...
> 
>> For example:
>> 	usb_cable: extcon-gpio-0 {
>> 		compatible = "extcon-gpio";
>> 		extcon-id = <EXTCON_USB>;
>> 		gpios = <&gpio6 1 GPIO_ACTIVE_HIGH>;
>> 	}
>> 	ta_cable: extcon-gpio-1 {
>> 		compatible = "extcon-gpio";
>> 		extcon-id = <EXTCON_CHG_USB_DCP>;
>> 		gpios = <&gpio3 2 GPIO_ACTIVE_LOW>;
>> 		debounce-ms = <50>;	/* 50 millisecond */
>> 		wakeup-source;
>> 	}
> 
> This is all 1 logical connector, the USB connector. Why are you 
> describing cables? Those are not part of the h/w and are dynamic. 
> Describe this as a connector which is one thing (i.e. node). Use a 
> compatible string that reflects the type of connector 
> (usb-microab-connector), not the driver you want to use. Then define 
> GPIO lines needed to provide state information like VBus, ID, charger 
> modes and control lines like soft connect (D+ pullup enable), VBus 
> enable, etc.

You're right. The extcon-gpio driver will not use the "extcon-gpio" raw compatible.
As you commented[1], the each connector will have the unique name to use the extcon-gpio.c driver.
[1] https://lkml.org/lkml/2015/10/21/906


For example,
The extcon-gpio.c driver may have the different name including the h/w information
according to the kind of external connector.

static const struct of_device_id gpio_extcon_of_match[] = {
	{
		.compatible = "extcon-chg-sdp",	/* SDP charger connector */
		.data = EXTCON_CHG_SDP_DATA,
	}, {
		.compatible = "extcon-chg-dcp",	/* DCP charger connector */
		.data = EXTCON_CHG_DCP_DATA,
	}, {
		.compatible = "extcon-jack-microphone", /* Microphone jack connector */
		.data = EXTCON_JACK_MICROPHONE_DATA,
	}, {
		.compatible = "extcon-disp-hdmi", /* HDMI connector*/
		.data = EXTCON_DISP_HDMI_DATA,
	},
	......
};

Thanks,
Chanwoo Choi