> On Thu, 21 Jun 2001, Jens Owen wrote:
> > Vladimir,
> > Your page looks very helpful. Thanks for putting it together. The only
> > comment I have is regarding your first miscellaneous comment:
> > "While hardware 3d is active nothing except your Xserver should be
> > accessing your video card - or your system will lockup hard. In
> > particular, frame grabber cards that write directly to video memory
> > should be turned off. If you want to use these cards try out v4l module
> > in XFree 4.x.x."
> > I think the intent of this message is good for users--but it's
> > misleading to developers trying to understand our architecture. To
> > clarify, direct rendering is completely based on the idea of a client
> > side driver accessing the hardware directly without using the Xserver to
> > exclusively access the device.
> > However, all access to the video device must be closely coordinated, and
> > come from a suite of drivers that know each other well. Using drivers
> > that don't cooperate closely, or even mixing older and newer driver
> > components can introduce the lockups you describe.
> > I hope this helps.
> Yes this does - thanks ! I'll put in a more general statement.
> The reason I wrote it this way is because r128 and radeon use so called
> "CCE engine" for 3d. Instead of writing 3d commands into registers they
> are written in a memory area and then DMA'ed up to the video card. So, my
> impression is that the client does not access the card as DMA setup is
> done by the dri driver or drm module. In particular, if one sets up bt848
> to dma stuff up to the card simultaneously with hardware GL you will get
> at the least engine timeout errors or (often) lockups.
> I think what I'll do is leave the statement as it is but create a note
> below for developers that explains how it really works. This way users get
> properly impressed and developers get the right info too.
Your updates look good.
Jens Owen / \/\ _
jens@... / \ \ \ Steamboat Springs, Colorado