From mboxrd@z Thu Jan  1 00:00:00 1970
From: linux@arm.linux.org.uk (Russell King - ARM Linux)
Date: Mon, 30 Jul 2012 15:24:43 +0100
Subject: [PATCH 2/2] ARM: dts: imx6q: Invert the GPIO controller order
In-Reply-To: <8E7BE7398BB9294F8B826ADE09B18EBE6CC2FF7EE1@SI-MBX20.de.bosch.com>
References: <1343219864-3040-1-git-send-email-dirk.behme@de.bosch.com>
 <1343219864-3040-2-git-send-email-dirk.behme@de.bosch.com>
 <20120728134114.GH2128@S2101-09.ap.freescale.net>
 <8E7BE7398BB9294F8B826ADE09B18EBE6CC2FF7EE1@SI-MBX20.de.bosch.com>
Message-ID: <20120730142443.GL6802@n2100.arm.linux.org.uk>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Mon, Jul 30, 2012 at 09:28:21AM +0200, Thomae Matthias (CM-AI/PJ-CF31) wrote:
> I care about the global number because it is used to access GPIOs
> from userspace via the Sysfs interface (see Documentation/gpio.txt).
> Without the 2 patches, the GPIOs are mapped this way:
> 
> gpiochip_add: registered GPIOs 224 to 255 on device: 209c000.gpio
> gpiochip_add: registered GPIOs 192 to 223 on device: 20a0000.gpio
> gpiochip_add: registered GPIOs 160 to 191 on device: 20a4000.gpio
> gpiochip_add: registered GPIOs 128 to 159 on device: 20a8000.gpio
> gpiochip_add: registered GPIOs 96 to 127 on device: 20ac000.gpio
> gpiochip_add: registered GPIOs 64 to 95 on device: 20b0000.gpio
> gpiochip_add: registered GPIOs 32 to 63 on device: 20b4000.gpio
> 
> With the patches, the mapping looks like this:
> 
> gpiochip_add: registered GPIOs 192 to 223 on device: 20b4000.gpio
> gpiochip_add: registered GPIOs 160 to 191 on device: 20b0000.gpio
> gpiochip_add: registered GPIOs 128 to 159 on device: 20ac000.gpio
> gpiochip_add: registered GPIOs 96 to 127 on device: 20a8000.gpio
> gpiochip_add: registered GPIOs 64 to 95 on device: 20a4000.gpio
> gpiochip_add: registered GPIOs 32 to 63 on device: 20a0000.gpio
> gpiochip_add: registered GPIOs 0 to 31 on device: 209c000.gpio
> 
> I.e. pin 0 on gpio1 is now accessed via /sys/class/gpio/gpio0
> instead of /sys/class/gpio/gpio224.

I think you're caring too much about the numbers you see within the Linux
kernel...

So what happens when your platform is built as part of a single zImage
along side a platform needing all the 256 GPIOs?  If the answer is "it
doesn't work" you need to go back and re-evaluate what you're doing.

Especially with DT, you shouldn't need to worry about the absolute GPIO
numbering.