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From: Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>
To: Hector Palacios <hector.palacios-i7dp0qKlBMg@public.gmane.org>
Cc: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
Subject: Re: GPIO polarity in bindings for Freescale MXS
Date: Thu, 14 Mar 2013 12:00:15 -0600	[thread overview]
Message-ID: <5142102F.3090309@wwwdotorg.org> (raw)
In-Reply-To: <5141A04D.8020805-i7dp0qKlBMg@public.gmane.org>

On 03/14/2013 04:02 AM, Hector Palacios wrote:
> Hello,
> 
> Maybe I'm missing something but the MXS processors (at least i.MX23 and
> i.MX28) cannot set the polarity of the GPIOs, so shouldn't the
> #gpio-cells be 1?
> 
> (From Documentation/devicetree/bindings/gpio/fsl-imx-gpio.txt):
> 
> - #gpio-cells : Should be two.  The first cell is the pin number and
>   the second cell is used to specify the gpio polarity:
>       0 = active high
>       1 = active low

This field describes how software should interpret the GPIO values.

So, if the GPIO is specified as active-high, then software will
gpio_set_value(the_value_it_wants), whereas if the GPIO is specified as
active-low, then software will gpio_set_value(!the_value_it_wants). Note
that "software" here refers to the driver that requests/uses the GPIO,
and the flags can be retrieve using of_get_gpio_flags().

      parent reply	other threads:[~2013-03-14 18:00 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-14 10:02 GPIO polarity in bindings for Freescale MXS Hector Palacios
     [not found] ` <5141A04D.8020805-i7dp0qKlBMg@public.gmane.org>
2013-03-14 12:35   ` Hector Palacios
     [not found]     ` <5141C423.7030202-i7dp0qKlBMg@public.gmane.org>
2013-03-15  5:24       ` Shawn Guo
2013-03-14 18:00   ` Stephen Warren [this message]

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