[PATCH 0/2] PV framebuffer

[Markus Armbruster <armbru@redhat.com>]

Summary of changes:

* Use xenbus_device API.

  Some xm configuration magic is still missing, see below.

* Negotiate features through Xen Store.

* Key identification

  Discussed at length on this list.  I fixed sdlfb to use scan codes
  (assumes standard AT or PS/2 keyboard).  vncfb is not fixable.  See
  comments in the code.

* Drop XENKBD_TYPE_BUTTON in favour of XENKBD_TYPE_KEY.  Simpler, and
  gets rid of the three button limit.

* Support shadow translate mode guests (untested).

* Absolute mouse pointer (optional feature)

* Fix event delivery and receipt notification.

* Use __s32 for coordinates instead of __u16 and __s16 for pixel
  coordinates, to match linux/input.h, which uses int.

* Don't drop the first pointer event on the floor in vncfb.

* Backends diagnose lost kbd events.

* Some renames to make xenkbd and xenfb drivers more similar.  Sorry
  for the extra diffs, but the inconsistencies were just too
  confusing.

Known issues:

* What to do when backend closes the connection?  I guess we want to
  keep the frontend running, ready for another connection.  This works
  already, but in a rather hackish and limited way.

* What to do when the frontend closes the connection?  Make backend
  exit?

* What happens when multiple backends connect to the same frontend?
  Chaos, most likely.

* Resume not implemented.

* xm configuration magic doesn't know the new devices, yet.  I'm
  ignorant of how this magic works, perhaps somebody can lend me a
  hand with it.

  Workaround:

  - Convert /etc/xen/FOO into FOO.sxp with xm create -n.  Make sure to
    delete the junk at the beginning of the output.

  - Add
        (device (vfb ()))
        (device (vkbd ())
    and change kernel and ramdisk to point to suitable copies.

  - xm create -F FOO.sxp.

* A couple of FIXMEs are still left in the code.

Future work:

* Investigate ditching LibVNCServer.

* Use grant tables when they become capable of mapping the
  framebuffer.

* Support multiple framebuffers.

* Dynamic screen resolution.

* Support other keyboards.