WSL2-USB-CAMERA

How to connect camera with WSL2?

Building your own USB/IP enabled WSL 2 kernel 5.10.102.1

Build kernel 5.10.102.1

I used a tool called USBIPD-WIN to recognize USB devices on Windows from WSL2 Linux.

However, USB cameras are not yet available in WSL2. This time I would like to solve this problem.

When using a USB camera on Linux, it is generally possible to use a mechanism called Video for Linux 2 (Video4Linux 2, V4L2).

Many recent USB cameras are compatible with USB Video Class (UVC), and it seems that there are many cases where USB cameras can be used in combination with V4L2 and UVC drivers.

Both "V4L2" and "UVC driver" are functions within the Linux Kernel, and the Linux Kernel must be made (compiled) with these features enabled.

Let's find out what happens with the WSL2 kernel I'm using. By the way, the Linux kernel version is as follows.

1. Check kernel version:

   uname -r

2. First, the V4L2 situation.

   zgrep CONFIG_VIDEO_V4L2 /proc/config.gz

Nothing is displayed. In other words, V4L2 is not enabled.

3. Also check the status of the UVC.

   zgrep CONFIG_USB_VIDEO_CLASS /proc/config.gz

Again, nothing is displayed. Therefore, it can be seen that the USB camera is not available in this Linux kernel provided in WSL2.

Get tools for compilation

Various tools are required to compile the Linux kernel.

4. In WSL, you can install the necessary set of tools with the following command.

   sudo apt-get update
   sudo apt-get install build-essential flex bison dwarves libssl-dev libelf-dev git libncurses-dev

You are now ready to get the tool.

Get Source

Next, get the source code of the Linux kernel.

5. Clone kernel branch linux-msft-wsl-5.10.102.1

   mkdir wsl-kernel
   cd wsl-kernel
   git clone https://github.com/microsoft/WSL2-Linux-Kernel.git -b linux-msft-wsl-5.10.102.1 --depth 1

This creates a directory called WSL2-Linux-Kernel, and the source code of the specified version of Linux Kernel is extracted in it.

You can see the source code here

Configuration

6. Run menuconfig to select kernel features to add.

   cd WSL2-Linux-Kernel
   make menuconfig KCONFIG_CONFIG=Microsoft/config-wsl

Note: Enable the following options. All should be enabled as built-in, not modules. The option should have an "*" next to it rather than an "M":

*「Device Drivers」→「Multimedia support」→「Filter media drivers」enable.

*「Device Drivers」→「Multimedia support」→「Media device types」→「Cameras and video grabbers」enable.

*「Device Drivers」→「Multimedia support」→「Media core support」→「Video4Linux options」→「V4L2 sub-device userspace API」enable.

*「Device Drivers」→「Multimedia support」→「Media core support」→「Media drivers」→「Media USB Adapters」→「USB Video Class (UVC)」and「UVC input events device support」enable.

*「Device Drivers」→「Multimedia support」→「Media core support」→「Media drivers」→「Media USB Adapters」→「GSPCA based webcams」enable.

The setting is overwritten and saved in "Microsoft/config-wsl".

Build

7. Build using the settings you saved earlier.

   make -j $(nproc) KCONFIG_CONFIG=Microsoft/config-wsl

Building takes quite a while. If it finally becomes "Kernel: arch/x86/boot/bzImage is ready" as follows, the build is successful.

The bzImage displayed in this last line will be the Linux kernel that was built and generated.

This file needs to be copied to the Windows side.

8. Create a folder called wsl in the Windows user directory (windows user) and copy it there. It will instantly display your username (terminal windows):

   echo %username%

   • I copied the created Linux Kernel with the file name bzImage-v4l2-uvc.

   mkdir -p /mnt/c/Users/<windows user>/wsl
   cp arch/x86/boot/bzImage /mnt/c/Users/<windows user>/wsl/bzImage-v4l2-uvc

Starting with the created Linux Kernel

9. In order to use the Linux kernel that you created yourself with WSL2, see . wslconfig" file should be created in the Windows user folder (windows user).

   nano /mnt/c/Users/<windows user>/.wslconfig

and the contents of this .wslconfig are as follows:

[wsl2]
kernel=C:\\Users\\<window user>\\wsl\\bzImage-v4l2-uvc

10. Once you have created the .wslconfig file, type the following command in PowerShell (or in a Windows terminal) to stop WSL2:

    wsl --shutdown

Then start WSL2 again.

11. When WSL2 starts, let's display the detailed information of Linux Kernel.

    uname -a

If the date and time displayed like this is the date and time of the build, it is started with the Linux kernel that you built yourself.

Using a USB camera

Once you've confirmed that WSL2 is working with the Linux kernel that supports V4L2 and UVC, try a USB camera.

This time, we are using the following USB camera.

First, use the Windows Package Manager install usbipd, detail usbipd-win:

winget install usbipd

12. Show list usb connected on windows

    usbipd wsl list

13. Next up is work on WSL

    sudo apt-get install linux-tools-5.4.0-77-generic hwdata
    sudo update-alternatives --install /usr/local/bin/usbip usbip `ls /usr/lib/linux-tools/*/usbip | tail -n1` 20

14. In this, find the device (USB camera) you want to use in WSL and remember its "BUSID"

    usbipd wsl attach -b "BUSID"

    • Example, in my case

    usbipd wsl attach -b 1-1

    • wsl detach can be used to stop sharing the device. The device will also automatically stop sharing if it is unplugged or the computer is restarted.

    usbipd wsl detach -b 1-1

15. From within WSL, run lsusb to list the attached USB devices. You should see the device you just attached and be able to interact with it using normal Linux tools.

    lsusb

16. When a USB camera is attached on the Windows side, it looks as if a USB camera has been connected from WSL2.

    • So let's run dmesg on the WSL2 side

    dmesg

If there is a line that begins with "uvcvideo" as follows, it is recognized as a UVC camera.

"uvcvideo: Found UVC ..."

If the line below is displayed. Don't worry, you need to change the camera and you're done:

"UVC non compliance - GET_DEF(PROBE) not supported. Enabling workaround."

17. When the USB camera is successfully recognized, a file (device node) starting with video is created under /dev.

    ls -l /dev/video*

18. With this permission, only users with root privileges can use the USB camera. This is inconvenient, so change the group to video so that the group can also be read and written.

    sudo chgrp video /dev/video*
    sudo chmod g+rw /dev/video*
    ls -l /dev/video*

19. Verifying in v4l-ctl:

    sudo apt-get install v4l-utils
    v4l2-ctl --all

20. USB camera image display:

    sudo apt-get install guvcview
    guvcview

If you check the terminal that started guvcview: "If you check the terminal that started guvcview". In such a case, try reducing the resolution in the control window of guvcview.

Summary

This time, I tried to use a USB camera in WSL2. Since the Linux kernel of WSL2 is not V4L2 or UVC enabled, you need to compile and replace the Linux kernel yourself to use the USB camera. If you change the Linux kernel, you can use a USB camera in WSL2 by combining it with USBIPD-WIN. However, it is a pity that there seems to be a difficulty in the transfer speed. Good luck!