On Tue, 21 Oct 2003, Ian Romanick wrote:

>> If DRI is disabled, then the Radeon driver will use the older
>> MMIO mechanism to do 2D acceleration.  I don't know what if any
>> of the other drivers will use DRI for 2D or Xvideo currently,
>> however any hardware that supports using DMA/IRQ for 2D
>> accelration or other stuff theoretically at least can use the DRI
>> to do it.
>
>I think that's the right model to follow.  Cards that can get benefit 
>should use the existing DRM mechanism, even if they don't support 3D.  I 
>believe that the i810 uses its DRM for Xv (or maybe it's XvMC...it's 
>something video related).

Agreed.  IMHO, all hardware support should have working 2D 
acceleration support without any hard requirement to have DRI 
enabled.

Optionally doing 2D via DRI is fine, but the only real benefit
IMHO of doing 2D with DMA/IRQ via DRI is if the driver also 
supports 3D acceleration using DRI.  If 3D via DRI is available, 
having the driver use the same mechanism to do both 3D and 2D 
acceleration is generally speaking superior.  In the case of the 
Radeon, it saves the problem of having to disable the running CP 
engine to do 2D then reenable the CP engine again to do 3D, etc. 
so doing it all via DRI in that case has a benefit.

But for a 2D only driver, DRI based 2D acceleration using DMA is 
more likely to be wasted effort than anything useful IMHO.  
That's probably why nobody has done it yet other than in the 
Radeon driver where it has a real good use.

I also think at least theoretically that Xv could benefit from
using DRI on more hardware, but I also think that is only
feasible for hardware in which there is existing and working DRI
3D acceleration.



-- 
Mike A. Harris

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