[Mesa-dev] DRM EGL swapbuffers?

[Thomas Hellstrom]

On 02/22/2011 07:44 PM, Chia-I Wu wrote:
> On Tue, Feb 22, 2011 at 1:56 AM, Thomas Hellstrom<thomas at shipmail.org>  wrote:
>    
>> Hi, Chia-I,
>>
>> Looking at the EGL DRM implementation of swapbuffers, it looks like we're
>> sort of ad-hoc attaching the backbuffer as a new scanout surface, using
>> drmModeSetCrtc.
>>
>> I don't think this works very well on all hardware. In particular, I think
>> drmModeSetCrtc may return before the swap actually takes place, which will
>> cause rendering to the old front buffer while it is still displaying.
>>
>> Could you fill me in why the pageflip ioctl isn't used here, and a surface
>> copy in situations where the pageflip ioctl can't be used? IIRC, the
>> pageflip ioctl is required to block rendering to the old frontbuffer until
>> the new frontbuffer is flipped in.
>>      
> Yes, pageflip should be used when available.  I did not use it simply
> because it was not available on my machine when the code was written,
> and I haven't had the motivation to revisit the code yet..
>
>    

OK. I'd like to update the code to use pageflip when available and 
otherwise fall back to a gallium blit. The current implementation really 
has no way to sync with ongoing rendering, and even if a synchronization 
method were implemented, draining the pipeline is generally a bad idea.

So what would the appropriate place be to implement an exported gallium 
blit utility function, callable from the platform drivers?

Thanks,
Thomas


>> Thanks,
>> Thomas
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