VT console blank ignored by DRM drivers on QEMU

[Gerd Hoffmann]

  Hi,

> But aside from that, can't we just teach these drivers to properly do
> dpms? With the atomic framework dpms is implement as simply turning
> the screen off, any driver should be able to support that properly.

Well, the virtual hardware simply has no dpms support, except maybe for
cirrus which mimics physical hardware.

bochs could toggle the blank bit in vga register space.

virtio and qxl could unmap the plane, but that might have unwanted
effects on the host side because qemu thinks the guest turned off the
display altogether.

> For the fbcon issue, can we perhaps just unconditionally ask fbcon to
> clear the screen when blanking? It's not really perf critical, so
> doing that for everyone shouldn't hurt.

Sounds good to me.

I've seen this on real hardware too btw (arm board with non-working
dpms).

cheers,
  Gerd