[V4L] RFC: Multiple capturing opens

Hi everybody,

As my last posting said, I am now busy coding the vbi driver for bttv2. 
The vbi spec for v4l2 has multiple capturing opens, and has the
resources being locked by the first open to S_FMT a format requiring the
resources.  The discussion we had earlier always had the resources being
locked at STREAMON time.

Here is my take on S_FMT vs STREAMON locking:
S_FMT - only need memory for two capture resources.
      - better defined capture states in capture engine.
      - no way of releasing resources without closing the open.
      - allows "feedback" so the app can determine which resources are
	currently available.
STREAMON - easier to do default contexts.
         - only lock the resources when we actually need them.

Any (more) comments suggestions appreciated.

(Gerd, could you please repost the URL for the multiple opens draft?  I
accidentally nuked that one.)

Thanks

-justin