Re: [PATCH] Add virtio gpu driver.

["Michael S. Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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