[$] Free user space for non-graphics drivers

In the kernel graphics world, there has been a longstanding "line in the sand" that disallows mergingkernel drivers without a corresponding free-software user-space driver. The idea is thatnot having a way to test the full functionality means that the kerneldevelopers cannot verify the proper functioning and security of thedriver; changes to the kernel driver may lead to unforeseen (anduntestable) problems on the user-space side. More recently, though, wehave seen other types of devices with complex drivers, but no useful freeuser-space piece, that have been proposed for inclusion into the kernel;at least one was merged, but the tide has perhaps turned against those typesof drivers at this point-or some of them, anyway.