feat: Add instructions for compiling Linux kernel for WSL2

Author: rprouse

wsl/kernel.md

@@ -0,0 +1,81 @@
+# Compile latest Linux kernel for WSL2
+
+In order to use a [USB WiFi card](./usb.md), you need to compile them into the Linux kernel.
+
+## Install build tools
+
+```sh
+sudo apt update
+sudo apt install -y \
+    build-essential flex bison \
+    libgtk-3-dev libelf-dev libncurses-dev autoconf \
+    libudev-dev libtool zip unzip v4l-utils libssl-dev \
+    python3-pip cmake git iputils-ping net-tools dwarves \
+    guvcview python-is-python3 bc
+```
+
+## Clone the Linux kernel
+
+```sh
+cd ~/src
+git clone https://github.com/microsoft/WSL2-Linux-Kernel.git wsl2-kernel
+```
+
+## Configure the kernel
+
+```sh
+cd ~/src/wsl2-kernel
+cp Microsoft/config-wsl .config
+make menuconfig
+```
+
+Under `Device Drivers -> Network device support -> Wireless LAN`, enable the WiFi drivers you need and save the configuration.
+
+## Build the kernel and install modules
+
+```sh
+make -j$(nproc)
+sudo make modules_install headers_install
+cp arch/x86_64/boot/bzImage /mnt/d/wsl
+```
+
+## Build the USBIP tools
+
+```sh
+cd tools/usb/usbip
+./autogen.sh
+./configure
+make -j$(nproc)
+sudo make install
+```
+
+## Install the custom kernel
+
+Exit and shutdown WSL2 with `wsl --shutdown`. Then create/edit a file `.wslconfig` in your Windows user directory.
+
+```ini
+[wsl2]
+kernel=d:\\wsl\\bzImage
+```
+
+Start a new WSL session and check the kernel,
+
+```sh
+$> uname -r
+6.6.36.3-microsoft-standard-WSL2+
+```
+
+## Drivers
+
+The following are as yet unsuccessful attempts to get WiFi drivers working.
+
+```sh
+sudo apt update
+sudo apt install firmware-misc-nonfree
+```
+
+```sh
+sudo modprobe vhci_hcd
+sudo modprobe mt76x2u
+lsmod
+```

wsl/usb.md

@@ -1,5 +1,7 @@
 # Connect USB device to WSL
 
+For WiFI drivers, you may need to [Recompile the Linux Kernel](./kernel.md).
+
 Install `usbipd`,
 
 ```sh