The fbdev_flush mechanism works great for targeting a single display. I would like to take advantage of the hardware stack on the RPi 4 and use both HDMI outputs. Currently when I write to /dev/fb0 both of my displays show the program output. I went looking to see if there was a secondary frame buffer (/dev/fb1) but there is not.
In doing research on this topic it seems that DRM is being used on the RPi4, and that to choose a display for my app, I will need to target the display through DRM (/sys/class/drm/card0 , card1 etc.)
Has anyone written a port for displaying selectively on the RPi4 yet? If so, could you help me get started? There doesn’t seem to be a lot of resources on how to use DRM to choose the output.
Please feel free to correct my assumptions. I’m still learning this framework.