I.MX6 Eglfs documentation
I have the following application:
Qt Widget application running on /dev/fb1 (overlay frame buffer), csi cam showing cam contents on /dev/fb0 (primary fb).
Qt widget has to run on overlay fb, because the application needs to overlay dynamic content on the video stream.
and here is the part which I did not exactly get:
bq. "When having multiple displays connected (e.g. the touch LCD panel and HDMI), there are two framebuffer devices: /dev/fb0 and /dev/fb2. Note that fb1 and fb3 are overlays for fb0 and fb2 and are not useful for our purposes here."
Is there a technical reason, why the overlay fb (fb1 or fb3) is not useful for eglfs?
There's no problem with using those, that wiki page just ignores the use case you have (overlaying something on top of some video) and instead talks about the simple case where you just want some (non-overlayed) content on a given screen.