[Mesa-dev] Dmabuf based render buffers!?

[Michel Dänzer]

On 2021-01-14 8:02 p.m., Blueroom wrote:
> 
> Hi Everyone!
> 
> I have a program that’s using dmabuf’s to create a zero copy camera->GL 
> texture pipeline and it’s working great on my RPi4.
> 
> Now as a last step I want to access the pixels that Iv’e processed in gl 
> with shaders, on the cpu.
> 
> Iv’e been told that on the Raspberry Pi OpenGL is sharing the same 
> memory as the cpu so I’m hoping it would be possible to do something 
> like a dmabuf on the ‘way out’ too?
> 
> Does anyone have any pointers in how this could work?

I'd recommend using glGetTexImage or other similar GL APIs for getting 
the data out of the GL texture.

While mmap of a dma-buf file descriptor works in theory, direct CPU 
reads from GPU accessible memory can be very slow on some platforms.


-- 
Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer