linux-kernel - RE: [PATCH] i2c-gpio.c: correct logic of pdata->scl_is_open

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Date:	Tue, 1 Nov 2011 06:59:46 +0100
From:	"Voss, Nikolaus" <N.Voss@...nmann.de>
To:	'Håvard Skinnemoen' <hskinnemoen@...il.com>
CC:	"'linux-arm-kernel@...ts.infradead.org'" 
	<linux-arm-kernel@...ts.infradead.org>,
	"'Linux Kernel'" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] i2c-gpio.c: correct logic of pdata->scl_is_open_drain

Hi Havard,

> {sda,scl}_is_open_drain indicates that the GPIO hardware is set up to
> do open drain so the software doesn't have to, i.e.
> gpio_set_value(pin, 1) will turn off the output driver rather than
> drive the pin high, so the _val functions will do the right thing.

gpio_set_value(pin, 1) drives the output high same as
gpio_direction_output(pin, 1) does (documented in Documentation/gpio.txt),
so the gpio will be changed from open-drain to push-pull.

In contrast, gpio_direction_input(pin) will turn off the output driver.

Open-drain io is bound to "!is_open_drain" and push-pull io is bound to
"is_open_drain", so I still think this should be the other way round.

Niko

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