Re: [PATCH] Add virtio gpu driver.

On Thu, Mar 26, 2015 at 08:12:39AM +0100, Gerd Hoffmann wrote:

On Mi, 2015-03-25 at 18:09 +0100, Michael S. Tsirkin wrote:

quoted

On Wed, Mar 25, 2015 at 04:37:16PM +0100, Gerd Hoffmann wrote:

quoted

  Hi,

quoted

BTW can we teach virtio-gpu to look for framebuffer using
virtio pci caps?

The virtio-gpu driver doesn't matter much here, it doesn't use it
anyway.

quoted

 Or are there limitations such as only
using IO port BARs, or compatibility with
BIOS code etc that limit us to specific BARs anyway?

Yes, vgabios code needs to know.  Currently it has bar #2 for the vga
framebuffer bar hardcoded.  It's 16bit code.  I don't feel like making
the probing more complicated ...

cheers,
  Gerd

OK - you are saying all VGA cards use bar #2 for this
functionality, so we are just following
established practice here?

vgabios checks pci ids to figure.  qxl+stdvga use bar #0, vmware-vga bar
#1, virtio-vga bar #2.

cheers,
  Gerd

And is it possible to use offset within BAR and/or memory BARs?
If yes I'd strongly prefer this.
As for writing 16 bit code, I need to do this for virtio scsi/blk
anyway, so we'll be able to share code.

-- 
MST