Red Hat's Mauro Carvalho Chehab has provided a large patch to the X.Org mailing list that migrate the xf86-video-v4l driver from using the V4L1 API to using V4L2. With the forthcoming Linux 2.6.38 kernel, the V4L1 API is removed entirely, which with the latest X.Org V4L DDX means it's broken. To fix this, Mauro has ported the driver to using the V4L2 API.
Video 4 Linux 1 had been around for quite a while (Linux 2.1 development, Linux 2.2) and Video 4 Linux 2 was then officially introduced with the Linux 2.6 kernel while bearing a compatibility mode for older Video 4 Linux 1 software. As Video 4 Linux 2 has been around long enough now, V4L1 support is now being ripped out of the kernel.
Besides just bringing this driver over to the V4L2, Red Hat's work also brings some other improvements to this driver as a result. It's considered a "Major rewrite, as driver got ported to V4L2 API." Looking at the size of the patch, this is indeed a major rewrite.
The patch can be found here.
This isn't all of the Video 4 Linux driver work that Mauro has been up to, but according to this message, there's still more. The xf86-video-v4l driver still uses some deprecated overlays in the X-Video extension and so Mauro is looking at porting the driver now to support Textured Video. This clean-up would result in xf86-video-v4l working with more drivers.