The dmabuf implementation in drm-kmod currently uses an ad-hoc DTYPE of 100 for dma-bufs with an XXX comment (and does nothing in dma_buf_fill_kinfo):
Defining a proper DTYPE_DMABUF and KF_TYPE_DMABUF would let procstat -f show us which file descriptors in a process are dma-bufs, which can be quite useful for debugging (e.g. recently I needed to see what kind of fd was failing to pass in Firefox).
Current drm side patch: https://reviews.freebsd.org/P431
TODO: edit procstat manpage, maybe display the size and device from kinfo in procstat