There was this post by a professional driver developer who wrote Linux drivers for the hardware company he works for. The problem he said, (I'm now paraphrasing

There was this post by a professional driver developer who wrote Linux drivers for the hardware company he works for. The problem he said, (I'm now paraphrasing) is that the kernel APIs kept changing and he had to keep reworking his drivers. Even though the driver code may be in the source tree, in the end it is still his job to keep it working. Linux may have POSIX outside, but its cause would be further advanced if they committed to stabler interfaces for driver developers.