Having the following kernel parameters:
video=mxcdi0fb:RGB24,1920x1080M@60 video=mxcdi2fb:RGB24,1920x1080M@60 hdmi di0_primary
Writing bytes into /dev/fb0, I can see the pixels on the display, that's ok.
Writing bytes into /dev/fb2, I can't see the pixels.
So fb0 is the background and I suppose it covers the foreground pixels. I suppose somehow the alpha of background should be changed or color keying should be used to make the foreground also visible.
I'd like to implement an OSD and using multiple framebuffers (one with the video data, another one with the OSD itself) seems to be a convenient way.
How can I adjust the color keying/opacity of each framebuffer? Is this possible at all?