RFC: hardware accelerated bitblt using dma engine

[Daniel Stone]

Hi,

On 4 August 2016 at 08:50, Daniel Vetter <daniel at ffwll.ch> wrote:
> One problem with 2d blitters is that there's no common userspace
> interface, but many: Xrender, hwc, old X drawing api, various attempts by
> khronos to standardize something, cairo, ... It's probably worse than
> video decoding even, and definitely not like on the 3d side where there's
> GL (and now vulkan) and that's it.

Running with the same theme, a unified API would only be meaningfully
useful if you have unified userspace support. As soon as you hit the
usual issues of needing to blit to/from special buffer types, weird
format restrictions, chained operations which can affect performance
enough to make you avoid or heavily favour certain types of
operations, etc etc, you'll need separate userspace code to handle
them. And at that point, sticking it behind a unified API doesn't
really bring any value.

Other prior art you could look at is the Renesas VSP1/VSP2 hardware,
which works through V4L2 and its media controller.

Cheers,
Daniel