Compiling Linux Kernel modules for Synology devices

Synology NAS are very versatile. They are running a stripped version of Linux with less kernel modules, but we can overcome this by compiling and adding modules (for instance the usbserial module used by usb serial converters).

Requirements:

• a computer (or a virtual machine) running Linux (Debian, Fedora, Ubuntu, etc)
• the tool chains specific to your Synology
• the Synology NAS GPL source specific to your Synology

How to proceed:

• Unzip the tool chains in /usr/local

	computer$ tar -xzf yourToolChains -C /usr/local/

• Unzip the Synology NAS GPL source inside your tool chains

	computer$ tar -xzf yourNASGPLSource -C /usr/local/yourToolChains/

• Before continuing, let’s find out which Linux kernel we are running on the Synology in order to compile for the right version:

computer$ ssh -l root ipOfYourSynology
synology$ uname -a
Linux Syno youLinuxKernelVersion xxxxx yourSynologyArchi

• Open the Synology NAS GPL source folder corresponding to your Synology Linux kernel

computer$ cd /usr/local/yourToolChains/source/linux-youLinuxKernelVersion

• Copy the config file created by Synology to configure the kernel

computer$ cp synoconfigs/yourSynologyArchi .config

• Edit the Makefile to compile for the right architecture and use the right tool chains

computer$ vi Makefile
edit the variable ARCH -> ARCH = yourSynologyAchi
edit the variable CROSS_COMPILE -> CROSS_COMPILE = /usr/local/yourToolChains/bin/yourToolChains-

• Check the config file we just copied

computer$ make oldconfig

• Edit the config file through the user interface to add modules

computer$ make menuconfig

• Compile all modules

computer$ make modules 
# or only a specific module: make M=./drivers/usb/serial

• Find your modules in the corresponding subfolder (in my case drivers/usb/serial/usbserial.ko)