This fork of the rga demo code from https://github.com/wzyy2/rga-v4l2-demo contains some test programs for the rockchip-rga usage on the Pine64 Pinenote device. This device has an epd display which can display 16-level grayscales, requiring conversion from RGB888 framebuffers to Y4, potentially with dithering-down support.
Preliminary support for Y4-conversion and dithering-down was added to the rockchip-rga v4l2 mem2mem driver in this repository:
https://github.com/m-weigand/linux/tree/mw/rk35/rk356x-rga
The program located in the subdirectory pn_03_drm_blitting_and_ctrls will display an image on the pinenote epd display.
RGB->Y4 conversion is done using the RGA hardware.
The RGA hardware can be controlled using key inputs, see the text printed on execution.