linux-kernel - Re: [PATCH] gpio: Add driver for MEN 16Z127 GPIO controller

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Date:	Fri, 16 Oct 2015 21:51:43 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Andreas Werner <andy@...nerandy.de>
Cc:	Alexandre Courbot <gnurou@...il.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Johannes Thumshirn <morbidrsa@...il.com>
Subject: Re: [PATCH] gpio: Add driver for MEN 16Z127 GPIO controller

On Thu, Oct 8, 2015 at 6:55 PM, Andreas Werner <andy@...nerandy.de> wrote:

> The register is currently impelemented as a read/write register
> which means the pin mode is configurable by software to
> Push Pull or Open Drain.

OK then you can set it in accordance to what clients request.

> There is also the possiblity (normal way) that the HW (FPGA) configures
> each pin to the correct mode.
>
> Is there actually a way to set an output mode from userland or by the gpio API?

As per <linux/gpio/machine.h> you can specify per-line if it should be
open drain using GPIO_OPEN_DRAIN, this will push through to the
gpio descriptor and those lines with this flag set will be handled specially.
We have merged device tree bindings for OD/OS but not code to
handle these, but I might have some code from Laurent Pinchart cooking
for the DT in-kernel backend too.

> I did not find anything about that.

git grep OPEN_DRAIN

Yours,
Linus Walleij
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