Camera board • buildroot libcamera: "No cameras were identified on the system"

• Hardware & Software
  • Board: Raspberry Pi Zero 2 W Rev 1.0
  • Camera: Camera Module 3, IMX708 module
  • OS: Custom Buildroot rootfs (64-bit, aarch64)
  • Kernel: Raspberry Pi Foundation kernel (cd231d47)
  • libcamera: Built and installed via Buildroot (0.5.0, mainline, not raspberrypi version)
• Symptoms
  • libcamera-apps is not installed. Should not be needed for my application, I think.
  • /dev/video0 exists, but it's the UVC gadget, not the camera
  • /dev/media* and /dev/video* for the camera do not appear
• What Works
  • Same hardware and camera module work perfectly with Raspberry Pi OS Lite (64-bit)
  • The camera shows up as expected in /dev/media* and /dev/video* on Raspberry Pi OS
• Kernel and Firmware Setup
  • Kernel source: raspberrypi/linux
  • Kernel commit: (tried multiple, including the latest as of 2025-05-18)
  • Defconfig: bcm2711_defconfig (as per official RPi docs for 64-bit)
  • DTB: bcm2710-rpi-zero-2-w.dtb
  • Overlays: Using official overlays, e.g., imx708.dtbo
  • config.txt:

    Code:

    start_x=1gpu_mem=128camera_auto_detect=1# For USB gadget modedtoverlay=dwc2,dr_mode=otg

  • All kernel, DTB, and overlay build dates match and are from the same build.
• Kernel Config Checks
  • I've confirmed the following kernel options are enabled (=y not =m):
    • CONFIG_MEDIA_CONTROLLER
    • CONFIG_MEDIA_SUPPORT
    • CONFIG_MEDIA_PLATFORM_SUPPORT
    • CONFIG_MEDIA_CAMERA_SUPPORT
    • CONFIG_V4L2_FWNODE
    • CONFIG_VIDEO_BCM2835_UNICAM
    • CONFIG_VIDEO_IMX708
    • CONFIG_V4L2_SUBDEV_API
    • CONFIG_I2C_CHARDEV
  • I disabled CONFIG_VIDEO_BCM2835_UNICAM_LEGACY
• Troubleshooting Steps Taken
  1. Tested hardware and camera with Raspberry Pi OS – works perfectly.
  2. Checked DTB and overlays:
     • Confirmed /mnt/bcm2710-rpi-zero-2-w.dtb and /mnt/overlays/imx708.dtbo match kernel build date.
     • strings on DTB shows correct nodes (linux,cma, etc.).
  3. Checked dmesg:
     • No probe errors, but also no evidence of Unicam/Cam sensor driver binding.
  4. /proc/device-tree/model confirms: Raspberry Pi Zero 2 W Rev 1.0
  5. Verified kernel version: Linux buildroot 6.12.20-v8 #3 SMP PREEMPT ... aarch64 GNU/Linux
  6. Confirmed udev (+eudev option) is running under BusyBox init system to create device nodes.
  7. No /dev/media* or /dev/video* nodes for camera after boot.
• Things I've Ruled Out
  • Hardware issue: Camera and cables work with Pi OS
  • DTB/overlay mismatch: All files are from same build
  • libcamera-apps dependency: On Pi OS works with and without libcamera-apps present.
• Questions
  • What else could be preventing the Unicam or camera sensor drivers from probing or binding to the hardware?
  • Could there be a kernel config or missing firmware file issue?
  • Does anyone have a working kernel .config for a 64-bit Buildroot + Pi camera setup on Zero 2 W?
  • Are there any other debugging steps or logs I should collect to pinpoint the issue?

Statistics: Posted by elcalzado — Mon May 19, 2025 3:43 am