linux-kernel - Re: [PATCH v3 1/3] extcon: extcon-gpio-usbvid: Generic USB VBUS/ID detection via GPIO

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Message-ID: <521F9CC9.4010004@wwwdotorg.org>
Date:	Thu, 29 Aug 2013 13:11:05 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	George Cherian <george.cherian@...com>
CC:	Chanwoo Choi <cw00.choi@...sung.com>, balbi@...com,
	myungjoo.ham@...sung.com, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
	grant.likely@...aro.org, rob@...dley.net, ian.campbell@...rix.com,
	mark.rutland@....com, pawel.moll@....com, rob.herring@...xeda.com,
	linux-omap@...r.kernel.org, linux-usb@...r.kernel.org,
	bcousson@...libre.com, davidb@...eaurora.org, arnd@...db.de,
	swarren@...dia.com, popcornmix@...il.com
Subject: Re: [PATCH v3 1/3] extcon: extcon-gpio-usbvid: Generic USB VBUS/ID
 detection via GPIO

On 08/29/2013 05:48 AM, George Cherian wrote:
> On 8/29/2013 4:07 PM, Chanwoo Choi wrote:
...
>> I tested various development board based on Samsung Exynos series SoC.
>> Although some gpio of Exynos series SoC set high state(non zero, 1) as
>> default value,
>> this gpio state could mean off state, disconnected or un-powered state
>> according to gpio.
>> Of course, above explanation about specific gpio don't include all gpios.
>> This is meaning that there is possibility.
>
> okay then how about adding a flag for inverted logic too.  something
> like this
> 
> if(of_property_read_bool(np,"inverted_gpio))
>     gpio_usbvid->gpio_inv = 1;
>
> And always check on this before deciding?

Don't do this. GPIO specifiers in DT typically include a "flags" cell
that describes certain GPIO properties. One of those properties is
signal inversion. You can use of_get_named_gpio_flags() to retrieve
those flags.
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