Trouble disabling bcm2708_fb and enabling vc4-kms-v3d on Raspberry

General Discussion
1

Hi everyone,

I’m trying to disable the bcm2708_fb framebuffer and enable vc4-kms-v3d (KMS driver with hardware acceleration) on my Raspberry Pi running DietPi OS, but without success so far.

What I understand:

  • bcm2708_fb is a legacy framebuffer driver.
  • It only supports software rendering, no GPU acceleration.
  • For full hardware acceleration (DRM/KMS, /dev/dri, Chromium acceleration), I should use vc4-kms-v3d instead.

Problem:

Even after multiple attempts, bcm2708_fb is still loaded at boot:

[ 0.596451] bcm2708_fb soc:fb: FB found 1 display(s)
[ 0.627463] Console: switching to colour frame buffer device 240x67
[ 0.631116] bcm2708_fb soc:fb: Registered framebuffer for display 0, size 1920x1080

What I have tried:

:white_check_mark: 1. Edited /boot/config.txt

I added:

dtoverlay=vc4-kms-v3d
gpu_mem=128
max_framebuffers=2
disable_fw_kms_setup=1

:white_check_mark: 2. Checked /boot/cmdline.txt

No mention of bcm2708_fb there — only standard entries like:

root=PARTUUID=503f5518-02 rootfstype=ext4 rootwait net.ifnames=0 logo.nologo console=tty1 video=HDMI-A-2:4096x2160d video=HDMI-A-1:4096x2160d snd_bcm2835.enable_headphones=0

:white_check_mark: 3. Tried blacklisting the module

Created /etc/modprobe.d/disable-bcm2708.conf with:

blacklist bcm2708_fb

:white_check_mark: 4. Rebooted after each change
Result:

Unfortunately, after reboot, bcm2708_fb still loads, and no /dev/dri exists.
As a result, Chromium runs without GPU acceleration, and the system is slow.

What is the correct procedure to completely disable bcm2708_fb on DietPi?

2

Did you tried using dietpi-config.

3

Actually, no. I will test it as soon as possible and share the result.

4

When you install Chromium via dietpi-software, the KMS driver should be enabled automatically. Though dtoverlay=vc4-kms-v3d is all that should be needed.

bcm2708_fb indeed always loads regardless, unless disabled with a custom overlay, but X11 should use DRI.

Does /sys/class/drm exist and contain the two HDMI screens you configure via cmdline?