Problem accessing IO port

I'm using a Mini2440 with PTXdist. I have an application that's been
running fine on my Mini2440 for the past year. The application uses quite a
lot of the IO ports on the Mini2440. I recently compiled a new PTX version
(2012.12.0) and is busy getting all the drivers working. I tested the IO
ports and found that I can't use IO port 199. I've been using this IO port
with the previous PTXdist version but now I get an error:

root@mini2440:~ echo 199 > /sys/class/gpio/export
sh: write error: Device or resource busy

I'm sure its not related to PTXdist itself but rather a driver clash.
Somewhere some driver is already using that IO port.

1.) How can I determine what process is currently using the IO port?
2) How can I resolve this problem?

Thank you

When you talk about "IO port 199" it mostly means an IO address you want to
access. But what you really want is to control a "GPIO" (which means a
physical pin, aka "general purpose IO").

To get an idea, who is using the GPIO 199 you can take a look into "cat
/sys/kernel/debug/gpio". If this file doesn't exist, mount the so called
"debugfs" into the "/sys/kernel/debug" directory, first.

Please note: There is no fixed correlation between a number and the
physical GPIO pin in Linux. It depends on the order the drivers register
their GPIOs.

Great! Thanks. The moment I executed "cat
/sys/kernel/debug/gpio" and read the result (gpio-199 Button5) I knew what
I did wrong. I remember enabling some button feature in the kernel!!

Keyboards -> GPIO Buttons

Thanks