pbuffers

[Keith Whitwell]

Brian Paul wrote:
> Jon Smirl wrote:
> 
>> It's going to take Brian, Keithw and myself another month or two to 
>> get a full
>> standalone OpenGL running. We are missing two major pieces of code, 
>> pbuffers and
>> mode support.
> 
> 
> I started looking at what it would take to get pbuffers going with 
> mesa-solo, in the r200 driver.  It looks like it'll be some work.
> 
> For rendering to off-screen color/depth/stencil buffers we need to pass 
> the buffer's start and stride to the kernel module.  Luckily, it looks 
> like that's transferred in the drm_radeon_context_regs_t structure, and 
> not fixed at initialization time.
> 
> However, this info seems to be ignored in the radeon_cp_dispatch_clear() 
> function; it seems to assume you're always clearing the front/back color 
> and depth/stencil buffers.
> 
> A work-around would be to draw a filled polygon to implement the clear, 
> but I'm wondering where else there might be similar assumptions to trip 
> us up.

Why not just fix the ioctl?

> The other thing we need is a mechanism to allocate the memory for 
> pbuffers.  My first guess is that this would have to be allocated out of 
> the space used for textures.  I think the DRI texture memory allocator 
> could be adapted to do this.

Correct.  There's a memory manager there for AGP space, but it's not 
integrated with the texture manager.  In the i830 driver, particularly the one 
on the agp-i865-0-1-branch, I have a kernel memory manager which integrates 
fairly smoothly with the client-driver's texture memory manager.  This is 
probably a decent starting point.

Keith