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Message-ID: <20150326091545-mutt-send-email-mst@redhat.com>
Date: Thu, 26 Mar 2015 09:18:01 +0100
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Gerd Hoffmann <kraxel@...hat.com>
Cc: virtio-dev@...ts.oasis-open.org, Dave Airlie <airlied@...il.com>,
Dave Airlie <airlied@...hat.com>,
David Airlie <airlied@...ux.ie>,
Rusty Russell <rusty@...tcorp.com.au>,
open list <linux-kernel@...r.kernel.org>,
"open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
"open list:VIRTIO CORE, NET..."
<virtualization@...ts.linux-foundation.org>,
"open list:ABI/API" <linux-api@...r.kernel.org>
Subject: 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:
> > 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
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