Patch by Richard Hosking: Userptr IO buffers need to be aligned according to the V4L2 reference capture c example (which has been updated with this recently). Also, the reference program has the device close operations after the 'free' calls so they have been moved. This fixes the issue I was having with my device crashing vlc on close. Also fixed a typo in an error message and renamed a local function which was badly named by me.