I was watching Crossroads when I saw this, I think it's a pretty cool song!
Sorry for putting this tab between John Mayer tabs but according to ultimate guitar Gary 
Clark doesn't exists;p
-Tom
^ = up stroke

\/ = down stroke

e|-5-----5-----5-----5-5|-5-----5-----5-----5-5|
B|-5-----5-----5-----5-6|-5-----5-----5-----6-5|
G|-5-----5-----5-----5-7|-5-----5-----5-----7-5|
D|-7-----7-----7-----7-7|-7-----7-----7-----7-7|
A|----------------------|----------------------|
E|----5-----5-----5-----|----5-----5-----5-----|
  \/  ^ \/  ^ \/  ^ \/ ^ \/  ^ \/  ^ \/  ^ \/ ^

I think this is what Gary plays..
Almost the whole song goes like this.

http://www.garyclarkjr.com/