Re: front/back buffer offsets in DRM

[Brian P. <bri...@tu...>]

Aapo Tahkola wrote:
> On Fri, 25 Nov 2005 16:16:48 -0700
> Brian Paul <bri...@tu...> wrote:
> 
> 
>>I've been playing around with the EGL r200 driver.  Digging through 
>>the framebuffer allocation code I've found a few problems.
>>
>>In order to support pbuffers and framebuffer objects we need to be 
>>able to work with color/depth/stencil buffers are various locations in 
>>video memory.
>>
>>The current code sets the front/back/depth buffer offsets and pitches 
>>once in the radeon_do_init_cp() function and there's no way to change 
>>them thereafter.
>>
>>It looks like the only code that uses this information is the glClear 
>>and SwapBuffers-related code in radeon_cp_dispatch_clear(), 
>>radeon_cp_dispatch_swap() and radeon_cp_dispatch_flip().  And the code 
>>that enables/disables color tiling.
>>
>>Could someone more familiar with the code comment on what it would 
>>take to fix the code so that color/depth buffers at arbitrary 
>>locations can be used?
>>
>>I'd probably do away with the front/back_offset/pitch fields entirely 
>>and pass the offset/pitch values as parameters to the ioctls.  I'd 
>>also write the code so there's no distinction between front/back color 
>>buffers.
> 
> 
> Whats the point of doing these operations in DRM anyway?
> Personally I would just pull out as much code from there as possible.

I was wondering about that too.  There may be some reason for doing 
those things in the kernel, but I don't know of any.

-Brian