Public bug reported:
This is for video4linux, libv4l or related.
There appears to be an issue in or around bcm2835-v4l2 not
detecting/configuring/exposing the second camera in Ubuntu Server
20.04.1 on the Raspberry Pi Compute Module 3+ hardware.
Followed the official instructions at
https://www.raspberrypi.org/documentation/hardware/computemodule/cmio-
camera.md and used the .dts file they supplied
(https://www.raspberrypi.org/documentation/hardware/computemodule/dt-
blob-dualcam.dts)
First, I confirmed that compiling the dt-blob.bin file and dropping it
to /boot/dt-blob.bin made it work in Raspberry Pi OS: I could capture
images from either of the cameras. (Expected behavior)
However, after switching to Ubuntu Server 20.04.1 (from
https://ubuntu.com/download/raspberry-pi) and compiling the same
suggested dual .dts and dropping it to /boot/firmware/dt-blob.bin the
system only provides /dev/video0. In both cases ‘start_x=1’ is present
in config.txt
It appears that the loop in
drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c is not
executed for each camera present and configured in RPi CM3+, resulting
in only one camera exposed to the end user. The value of
MAX_BCM2835_CAMERAS of 2 should be respected; something in the
code/default configuration/environment is affecting this functionality.
Here’s what I see in dmsg:
Raspberry Pi OS:
[7.674728] videodev: Linux video capture interface: v2.00
[7.740370] bcm2835-isp bcm2835-isp: Device node output[0] registered as
/dev/video13
[7.740908] bcm2835-isp bcm2835-isp: Device node capture[0] registered as
/dev/video14
[7.741486] bcm2835-isp bcm2835-isp: Device node capture[1] registered as
/dev/video15
[7.742841] bcm2835-isp bcm2835-isp: Device node stats[2] registered as
/dev/video16
[9.004310] bcm2835-codec bcm2835-codec: Device registered as /dev/video10
[9.013003] bcm2835-codec bcm2835-codec: Device registered as /dev/video11
[9.022054] bcm2835-codec bcm2835-codec: Device registered as /dev/video12
[9.025325] bcm2835-v4l2: V4L2 device registered as video0 - stills mode >
1280x720
[9.033622] bcm2835-v4l2: Broadcom 2835 MMAL video capture ver 0.0.2 loaded.
[9.062931] bcm2835-v4l2: V4L2 device registered as video1 - stills mode >
1280x720
[9.068984] bcm2835-v4l2: Broadcom 2835 MMAL video capture ver 0.0.2 loaded.
$ v4l2-ctl --list-devices
bcm2835-codec-decode (platform:bcm2835-codec):
/dev/video10
/dev/video11
/dev/video12
bcm2835-isp (platform:bcm2835-isp):
/dev/video13
/dev/video14
/dev/video15
/dev/video16
mmal service 16.1 (platform:bcm2835-v4l2):
/dev/video0
/dev/video1
Ubuntu 20.04.1:
[ 12.700652] videodev: Linux video capture interface: v2.00
[ 12.995520] bcm2835-isp bcm2835-isp: Device node output[0] registered as
/dev/video13
[ 12.995871] bcm2835-codec bcm2835-codec: Device registered as /dev/video10
[ 12.995953] bcm2835-isp bcm2835-isp: Device node capture[0] registered as
/dev/video14
[ 12.997342] bcm2835-isp bcm2835-isp: Device node capture[1] registered as
/dev/video15
[ 12.997740] bcm2835-isp bcm2835-isp: Device node stats[2] registered as
/dev/video16
[ 13.003552] bcm2835-codec bcm2835-codec: Device registered as /dev/video11
[ 13.011487] bcm2835-codec bcm2835-codec: Device registered as /dev/video12
[ 14.258871] bcm2835-v4l2: V4L2 device registered as video0 - stills mode >
1280x720
[ 14.264316] bcm2835-v4l2: Broadcom 2835 MMAL video capture ver 0.0.2 loaded.
$ v4l2-ctl --list-devices
bcm2835-codec-decode (platform:bcm2835-codec):
/dev/video10
/dev/video11
/dev/video12
bcm2835-isp (platform:bcm2835-isp):
/dev/video13
/dev/video14
/dev/video15
/dev/video16
mmal service 16.1 (platform:bcm2835-v4l2):
/dev/video0
Note the log line ‘V4L2 device registered as video1’ is not reported in
Ubuntu.
In terms of hardware the cameras are configured properly and detectable;
the hardware is exactly the same, the only difference is the OS which is
swapped by means of swapping microSD cards containing Raspberry Pi OS
and Ubuntu 20 respectively.
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:Ubuntu 20.04.1 LTS
Release:20.04
Codename: focal
** Affects: libv4l (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1904306
Title:
bcm2835-v4l2 does not detect/expose the second camera on RPi Compute
Module 3+ in Ubuntu Server 20.04.1
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