My experience is that vendors have written very few of the drivers in the Linux kernel, and that most vendor drivers remain proprietary. Nvidia's being the most visible, Intel Poulsbo's being another despised example, most of Android's drivers are also closed and hiding behind an extensive shim framework, Dell even wrote DKIM to help deal with all of the proprietary vendor drivers for the subset of machines on which they offer Linux.

Linux's wealth of open source drivers seem to come almost exclusively from it's community, instead. Which, but for a Finnish university student, could have just as easily coalesced around FreeBSD.