The game can have controller support activated through the console.
control + alt + Shift + ~ will bring up the console command
type in this:
+set g_EnablePCControllerInput 1
For more information on configuring the gamepad, http://www.splashdamage.com/forums/showthread.php?t=27506
If you're sick of doing this everytime, i'd suggest getting a gamepad mapper like http://www.softpedia.com/get/System/System-Miscellaneous/Xpadder.shtml and making a controller profile for Brink. Its really easy with Xpadder!