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.