# Compiling kernel modules for the ClearFog CX LX2 **URL:** \ **Category:** NXP LX2160\ **Created:** [May 10, 2022, 9:38am UTC](https://community.solid-run.com/t/compiling-kernel-modules-for-the-clearfog-cx-lx2/314 "2022-05-10T09:38:31Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![robert\_sv](https://avatars.discourse-cdn.com/v4/letter/r/e0b2c6/32.png) [@robert\_sv](https://community.solid-run.com/u/robert_sv)\ **Post date:** [May 10, 2022, 9:38am UTC](https://community.solid-run.com/t/compiling-kernel-modules-for-the-clearfog-cx-lx2/314/1 "2022-05-10T09:38:31Z")
Hello, How do we compile kernel modules (a camera device driver in our case) for the ClearFog CX LX2? `/lib/modules/$(uname -r)/build` is empty after installing a pre-built image. Are the kernel headers and binaries distributed anywhere? I tried to build an image, and headers, myself by following this process: 1. Following the steps here, built an image with docker on an x86-64 machine, based on commit bc46e34: [GitHub - SolidRun/lx2160a\_build: Scripts to build basic images for LX2160A COM express type 7 modules](https://github.com/SolidRun/lx2160a_build) 2. Flash the ClearFog board with the created image file. 3. Copied the `lx2160a_build/build/linux` directory to the ClearFog board. 4. Unfortunately, copying the contents of the `linux` directory into `/lib/modules/$(uname -r)/build` and then compiling the kernel module did not work. This is because the docker container used the host compiler rather than the cross-compiler when compiling the contents of `build/linux/scripts`, as well as some other files. It’s apparently quite common for kernel cross-compilation setups to let the host compiler leak through, according to some online searches. 5. Run `make scripts -j16 LOCALVERSION="-00007-g9c7b74fdbb19"` and `make modules -j16 LOCALVERSION="-00007-g9c7b74fdbb19"` inside the `linux` directory, on the ClearFog, to build the kernel. I had to specify the LOCALVERSION, otherwise the kernel’s release string will would simply be `5.4.47-generic` (If I recall correctly), rather than the system’s actual `uname -r` output of `5.4.47-00007-g9c7b74fdbb19`. Kernel module compilation would fail if they were mismatched. I don’t know why this is necessary, as I can’t see where the docker container sets any version string. 6. Copy the `linux` directory’s contents into `/lib/modules/$(uname -r)/build` and then build the kernel module. It successfully built and the module was then loaded. Unfortunately, the camera API produced a non-descriptive error when I attempted to connect to the camera, using this driver. I can think of a few issues with my process: - In step 5, compiling the kernel headers with the ClearFog used the system’s default GCC version. However, the actual kernel itself was compiled with a specific version of GCC Linaro as defined in the Docker container. ABI issues, perhaps? - In step 5, certain config was lost when building the kernel headers. I don’t understand where the Docker container produces the `5.4.47-00007-g9c7b74fdbb19` string to the kernel name, and why I need to manually specify it when building on the ClearFog. Other settings may have been lost. - The driver compiled fine, but it’s an issue with the camera itself, or the way the camera interfaces with this particular ARM board. Is there a simpler way to build the kernel headers, or be provided them prebuilt? ---
**Author:** ![jnettlet](https://dub1.discourse-cdn.com/flex005/user_avatar/community.solid-run.com/jnettlet/32/62_2.png) [@jnettlet](https://community.solid-run.com/u/jnettlet)\ **Post date:** [May 10, 2022, 12:21pm UTC](https://community.solid-run.com/t/compiling-kernel-modules-for-the-clearfog-cx-lx2/314/2 "2022-05-10T12:21:59Z")
If you are building your own image, then I would recommend just tweaking the kernel config file to include the kernel modules you need for your hardware. ---
**Author:** ![robert\_sv](https://avatars.discourse-cdn.com/v4/letter/r/e0b2c6/32.png) [@robert\_sv](https://community.solid-run.com/u/robert_sv)\ **Post date:** [May 10, 2022, 2:49pm UTC](https://community.solid-run.com/t/compiling-kernel-modules-for-the-clearfog-cx-lx2/314/3 "2022-05-10T14:49:05Z")
It’s an out-of-tree module. Would it make sense for me to add the kernel’s source code to `linux/drivers` in the container, tweaking the makefiles and Kconfig files so it’s part of the build? ---
**Author:** ![jnettlet](https://dub1.discourse-cdn.com/flex005/user_avatar/community.solid-run.com/jnettlet/32/62_2.png) [@jnettlet](https://community.solid-run.com/u/jnettlet)\ **Post date:** [May 10, 2022, 2:52pm UTC](https://community.solid-run.com/t/compiling-kernel-modules-for-the-clearfog-cx-lx2/314/4 "2022-05-10T14:52:23Z")
that is probably easiest. Newer distributions should have the hardware supported in kernels 5.14 and newer with device-tree if you want to try a packaged kernel. ---
**Author:** ![womble](https://dub1.discourse-cdn.com/flex005/user_avatar/community.solid-run.com/womble/32/114_2.png) [@womble](https://community.solid-run.com/u/womble)\ **Post date:** [May 10, 2022, 4:11pm UTC](https://community.solid-run.com/t/compiling-kernel-modules-for-the-clearfog-cx-lx2/314/5 "2022-05-10T16:11:30Z")
It’s probably easiest to cross-compile the module on the host: $ cd \ $ export PATH=$ROOTDIR/build/toolchain/gcc-linaro-7.4.1-2019.02-x86\_64\_aarch64-linux-gnu/bin:$PATH $ export CROSS\_COMPILE=aarch64-linux-gnu- $ export ARCH=arm64 $ make -C \ M=$PWD \ ---
**Author:** ![jnettlet](https://dub1.discourse-cdn.com/flex005/user_avatar/community.solid-run.com/jnettlet/32/62_2.png) [@jnettlet](https://community.solid-run.com/u/jnettlet)\ **Post date:** [May 10, 2022, 4:19pm UTC](https://community.solid-run.com/t/compiling-kernel-modules-for-the-clearfog-cx-lx2/314/6 "2022-05-10T16:19:31Z")
that will also work for a one off module.