The direct userspace access support included with the kernel's InfiniBand drivers in kernels 2.6.13 and newer creates character devices named uverbs0, uverbs1, etc. Please add a udev rule: KERNEL="uverbs*", NAME="infiniband/%k", MODE="0660", GROUP="rdma" to create the device nodes. As you can see, I am suggesting that these nodes be owned by an "rdma" group. This is analogous to other groups used for device nodes, such as "dialout" or "cdrom" -- the uverbs devices are fairly safe to allow ordinary users access to, but an administrator should be able to control which users can use the device. I suggest the name "rdma" for the group name because these device nodes give userspace programs access to RDMA capabilities from InfiniBand and (someday) iWARP hardware. Of course, this requires the creation of the rdma group. I'm not sure where or how this sort of group is managed, so please let me know if there's any other avenues I should be sending this request to.
Which userspace apps?
Apps will generally use this through an MPI library such as Open MPI (http://open-mpi.org) or MVAPICH (http://nowlab.cse.ohio-state.edu/projects/mpi-iba/). These libraries access InfiniBand through the libibverbs library, which I have packaged for Fedora Extras (open request for review in bug 169743).