[ydl-gen] Video Monitors--2

[David Seikel]

On Tue, 9 Jan 2007 12:33:33 -0800 jmzorko at mac.com wrote:

> > 1) Will there ever be a way to access the video card directly?  The
> > drivers already exist, I think.  We don't need anything crazy
> > either, just some way to watch video in 1080P.  So the open-source
> > nvidia X driver may just work if the hardware was accessible.  If
> > nVidia or Sony give us a binary-only 2D-accelerated video driver,
> > that's great.
> 
> I doubt this -- on the Xbox 360 as well as the PS3, I believe all  
> code runs under a hypervisor e.g. it "virtualizes" everything, so no  
> code outside of the hypervisor ever accesses hardware directly (for  
> some evidence, do a "df -k" in bash while running YDL, and notice  
> that you never see the partition Sony made for GameOS -- the kernel  
> knows nothing about it because the hypervisor is only letting the  
> kernel see the non-GameOS partition for Linux).  That being said, if  
> this is true then obviously the hypervisor is accessing the video  
> hardware (on behalf of PS3 games in GameOS mode, and X while running  
> Linux), so the games are asking more of the hypervisor than YDL is.   
> Perhaps Sony hasn't given YDL the means to do this, or perhaps YDL  
> hasn't implemented it yet, or perhaps i'm completely wrong?

You are correct about the PS3's hypervisor, it controls all access to
the hardware, except USB which seems to go direct.  I have no clue
about the Xbox 360.

The hypervisor only allows access to a framebuffer, and even then it's
not direct access.  The linux side writes to a frame buffer in main
memory, then uses the hypervisor to trigger a DMA transfer that copies
this to the real frame buffer on the GPU.

It should be possible for applications to use the SPE's to accelerate
rendering to this internal frame buffer, but that will likely have to
be done one app at a time.  This could probably be done for both 2D and
3D.  An SPE port of the OpenGL software renderer could do good things
for 3D apps for instance.
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