linux-kernel - Re: [PATCH] of/gpio: Define OF_GPIO_OPEN

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Date:	Tue, 11 Feb 2014 13:31:44 +0900
From:	Alexandre Courbot <gnurou@...il.com>
To:	David Daney <ddaney.cavm@...il.com>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH] of/gpio: Define OF_GPIO_OPEN_DRAIN flag for Open Drain outputs.

On Tue, Feb 11, 2014 at 7:05 AM, David Daney <ddaney.cavm@...il.com> wrote:
> From: David Daney <david.daney@...ium.com>
>
> When we have a GPIO pin connected to an open-drain network, we want a
> standard way of specifying this in the device tree.  So we choose bit
> 1 of the flag field to indicate open drain.
>
> A typical use case would be something like:
>
>         enum of_gpio_flags f;
>         .
>         .
>         .
>         reset_gpio = of_get_named_gpio_flags(node, "reset", 0, &f);
>         .
>         .
>         .
>         ret = gpio_request_one(reset_gpio,
>                 (f & OF_GPIO_OPEN_DRAIN) ? GPIOF_OPEN_DRAIN : 0,
>                  "reset");
>         .
>         .
>         .
>         gpio_direction_output(reset_gpio, 1);
>         gpio_set_value(reset_gpio, 0);
>         msleep(20);
>         gpio_set_value(reset_gpio, 1);

This is also useful for gpiod_get(). However, while you are at it,
could you also add a flag for the OF_GPIO_OPEN_SOURCE property? My joy
would be complete if you could also take the time to update
of_find_gpio() to pass these new flags back to the caller as it
already does for OF_GPIO_ACTIVE_LOW.

Then you could even switch your use-case to the gpiod interface and
not bother with passing these flags by yourself anymore. Just sayin'.
;)

Thanks,
Alex.
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