Graphics, sound and multimedia • Pi 4B: No fb1 Created for HDMI1 when using AV Jack and HDMI0 (Legacy/DRM Conflict?)

Hi everyone,

I’m setting up a Raspberry Pi 4B with the following configuration:
•HDMI1 for management (desktop environment or terminal access).
•HDMI0 for media playback output.
•AV jack for video output to an RF modulator connected to a retro TV.

The issue is that no /dev/fb1 is created for HDMI1, even though:
1.HDMI1 is working (I can see the desktop and manage the Pi from it).
2.HDMI0 and the AV jack share /dev/fb0, as expected.
3.DRM detects both outputs (/dev/dri/card0 and /dev/dri/card1).

What I’ve Tried:
1.Configuring HDMI and AV Jack in config.txt:
•Enabled enable_tvout=1, sdtv_mode=2, and sdtv_aspect=1 for the AV jack.
•Forced hdmi_force_hotplug:0=1 and hdmi_force_hotplug:1=1 to ensure both HDMI ports are active.
2.Using FKMS and KMS Drivers:
•FKMS initializes /dev/fb0 for HDMI0 and the AV jack but doesn’t create fb1 for HDMI1.
•KMS didn’t resolve the issue either.
3.Direct DRM Tests:
•Both /dev/dri/card0 (HDMI0) and /dev/dri/card1 (HDMI1) are present.
•I can output to HDMI1 via DRM, but no framebuffer (fb1) exists.

Statistics: Posted by RetroPi — Wed Jan 22, 2025 10:09 pm — Replies 0 — Views 23

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