Re: [Qemu-devel] [SeaBIOS] [RFC PATCH v2] fw/pci: Add support for mapping Intel IGD OpRegion via QEMU

[Gerd Hoffmann]

  Hi,

> > +    if (file->copy(file, opregion, file->size) < 0) {
> Is opregion content on host immutable?
> if not then copying it probably wrong and it should be passed-through.

The OpRegion is used for communication between bios and driver, it is
*not* something going directly to the hardware.  There is also the VBT
(video bios table) with some configuration information (most notably
laptop panel info).  The latter will be used by the guest driver.

To make stuff like brightness control work is is not enough to
pass-through the opregion, we would also have to somehow forward acpi
notifications and acpi calls between host and guest, so the guest driver
can talk to the host bios.  That is seriously non-trivial, for little
(if any) gain.

cheers,
  Gerd