Building a Kernel Module for OpenWRT: My Unexpected Deep Dive

A few days ago, I found myself needing a very specific WiFi driver (kmod-mt76x2) for OpenWRT 23. Instead of hunting for precompiled .ipk packages or praying for a miracle in some forgotten GitHub issue, I rolled up my sleeves and decided to build the module myself — the hard way. Here's how it went.

☁️ My Setup

• 2 CPU cores
• 4 GB RAM
• About 30 GB of storage
• Host Kernel: 6.1.0-18-amd64
• OpenWRT target kernel: 6.6.73

🔄 Step-by-Step Overview

1. Cloning the OpenWRT Source

git clone https://git.openwrt.org/openwrt/openwrt.git
cd openwrt

I stuck with the openwrt-23.05 branch to match my router firmware.

2. Installing the Essentials

sudo apt update
sudo apt install build-essential clang flex bison g++ gawk gcc-multilib \
  gettext git libncurses-dev libssl-dev python3-distutils rsync unzip \
  zlib1g-dev file wget python3 python3-pip python3-setuptools

Optional: ccache and ninja-build for faster builds.

3. Configuring the Build

./scripts/feeds update -a
./scripts/feeds install -a
make menuconfig

In the menu:

• Target system: match your OpenWRT device
• Package → Kernel Modules → Wireless Drivers → ✅ kmod-mt76x2 (M or *)

Then save the config and run:

make -j1 V=s

Note: I used -j1 to avoid RAM overload on my small VM.

4. Running Into Errors? Yup.

Midway through, tools/tar failed because I was running as root. Solution?

export FORCE_UNSAFE_CONFIGURE=1
make -j1 V=s

Patience was key here. CMake alone took over 40 minutes. But it was satisfying watching those lines tick up: [512/862] and counting.

📦 So Where's the .ko File?

Once the build finishes, the kernel object file (mt76x2e.ko) should be inside:

build_dir/target-*/linux-*/mt76x2*/mt76x2e.ko

From here, I can:

• Copy it to my OpenWRT router
• Use insmod to load it
• Or package it as a .ipk for deployment

More on that in Part 2 😉

🤔 Why I Did This

Honestly, it was part curiosity, part necessity. I didn't want to rely on outdated binaries or third-party repos. And now, I've got a custom kernel module, fully aligned to my current kernel version.

Also? It's fun. Frustrating at times, but fun.

💬 Lessons Learned

• 2 cores and 4 GB RAM can build OpenWRT — just bring coffee.
• Always check your kernel versions between host and target.
• Don't run configure scripts as root unless you really have to.
• This whole thing makes you appreciate package maintainers so much more.

Got questions about building OpenWRT packages or kernel modules? Drop me a message. Happy to share notes!