Use GPIO directory based on actual device tree path

[VipSaran]

By testing the device tree directory we can detrermine whether to use the "old" /sys/devices/virtual/gpio path or to use the one used after update to kernel 3.18.x: /sys/class/gpio, so both configurations are supported.

[jfriend00]

This diff changes basic code formatting in ~50 places such that it is next to impossible to find what the functional change were to the code. This would be a much better submission if the diff was only the functional changes.

[VipSaran]

Fixed with commit VipSaran@2636804 (reverted the whitespace changes).

[jfriend00]

Finally found a way to see just the "net" diff: master...VipSaran:master

[VipSaran]

@jfriend00 you "found the way" becuse I added another commit to the pull request, just as I commented above.

[jfriend00]

@VipSaran - I know you added another commit. But even then, neither one of your commits made it easy to see the "net" diff so I had to find a way to see a diff between two non-sequential versions on Github. That's what I had to "find". I'm not a github expert so you weren't making it easy to see the meaningful diff which is what I cared about - even with your additional commit. When I found out how to do it, I thought I'd share so others could likewise just click on a link to see what functionally changed.

[VipSaran]

You don't have to be an expert. Just open Pull Request / Files Changed tab and you see the absolute difference between the upstream and the fork:

[lurch]

AFAIK you shouldn't ever need to use /sys/devices/virtual/gpio and you should always just use /sys/class/gpio, regardless of whether DeviceTree is being used or not?
As raspberrypi/linux#791 (comment) explains.

[bestander]

👍 can this be merged please?

[jsavko]

This patch also makes it work with the Raspberry Pi 2 B. I was testing it last night.

[rakeshpai]

Published to npm as 0.0.7. Thanks, @VipSaran @jfriend00 @jsavko.

[VipSaran]

Thanks @rakeshpai