N900 camera is capable to produce RAW output. However, v4l2camsrc does not give it by default to an application, you need to do tricks outlined in camerabin example in gstreamer.

Another problem is that V4L2 is not very useful for controlling still photography. It lacks certain things and giving large set of control points (80+ ioctls with many sub-controls), all asking for reorganization... For example, it is not possible to get per-frame information about parameters this frame was taken with, even though main camera on N900 is capable to return this information as part of its data flow.

Maker Note contains some information about the parameters but it is encrypted and encoded and currently algorithm for decoding it is not public.

It would be relatively simple (example code is there, in camerabin examples in gstreamer) to write a gstreamer plugin that saves RAW frame data in parallel to shooting and processing JPEG image. It will work with Nokia-provided camera as well, user would need to modify some settings in the configuration file. Perhaps Christmas time would give me some space to write up a summary of what is published on maemo.gitorious.org already.