Access gpio 150 (user LED) problem

I have a Beagleboard xM Rev B. I am new to the Beagleboard and Unix,
but I managed to get Ubunto 10.10 up and running on it.

I have tried to access the user LED on GPIO150 using example commands
on the web (echo 150 > export) when I try this and look in /sys/class/
gpio I find no gpio150 directory. If I try the same command with echo
15 … it creates a directory gpio15.

Why is it not creating the gpio150 directory?

Ernie

I have a Beagleboard xM Rev B. I am new to the Beagleboard and Unix,
but I managed to get Ubunto 10.10 up and running on it.

I have tried to access the user LED on GPIO150 using example commands
on the web (echo 150 > export) when I try this and look in /sys/class/
gpio I find no gpio150 directory. If I try the same command with echo
15 … it creates a directory gpio15.

Why is it not creating the gpio150 directory?

Read the ‘dmesg’ log to see if it provides any clue, but the answer is that it is allocated already to the leds-gpio driver. Linux won’t just unallocate it for you, you have to free the GPIO that is under use by a different driver first.

Jason,
  Thanks for your comments. It makes sense about the already installed
driver, I assume there is a method in Unix to either unload the driver
or prevent it from being loaded in the first place. What affect would
unloading the driver have to any application trying to access the LEDs
through the driver?
Is using the driver a more efficient way of controlling the gpio pins
than using setting the value in /sys/class/gpio/gpioxx?
Why when using the ‘echo 150 > export’ command does it not return an
error to indicate the problem?

  Thanks for your time Ernie