[PATCH][MTD] mtdpart.c: allow other drivers to get physical address of partition

[Carsten Otte]

Jörn Engel wrote:
> Neither am I.  My missing puzzle piece is how to zap all page mappings
> for the chip in question.  Maybe the fs/vm meeting at lce will clear
> things up.
I don't think that one is particular hard to do. All you need is:
- count refernces in the driver
- make the xip code return its references after use
- a callback that the driver can call to get its references that are
   mapped to userland back which would simply boil down to 
filemap_xip_unmap()
- the driver should stop handing out new references for file 
operations when calling the callback, and the reference count should 
become zero pretty soon.
I'd be happy to do the xip infrastructure parts of this.