Fedora 26 – RTL8188EU the Hard Way!

Following my former entry preaching on the greatness of Fedora 26, I decided to share some wisdom regarding USB wireless adapters (aka dongles) with the Realtek RTL8188EU chip. These and many other Realtek-based (usually RTL8188EU and RTL8192CU) adapters are affordable and extremely common. Companies like Hama, Digitus, TP-LINK and Belkin fit them into the cheapest 150N and 300N dongles, claiming that they’re compatible with Linux. In principle, they are. In practice, the kernel moves so fast that these companies have problems keeping up with driver updates. As a result,  poor quality drivers remain in the staging kernel tree. Some Linux distributions like Debian and Ubuntu include them, but Fedora doesn’t (for good reasons!) so Fedora users have to jump through quite some hoops to get them working…

The standard approach is to clone the git repository for the stand-alone RTL8188EU driver, compile it against our kernel + headers (provided by the Linux distribution of choice) and modprobe load if possible. Alas, since the stand-alone driver isn’t really in-sync with the kernel, it often requires manual patching and is in general quite flaky. An alternative, more fedorian approach is to build a custom kernel with the driver included. The rundown is covered by the Building a custom kernel article from the Fedora Wiki. All configuration options are listed in the various kernel-*.config files (standard kernel .config files prepped for Fedora), where “*” defines the processor architecture. Fortunately, we don’t have to mess with the kernel .configs too much, merely add the correct CONFIG_* lines to the “kernel-local” text file and fedpkg will add the lines prior to building the kernel. The lines I had to add for the RTL8188EU chip:

# ‘m’ means ‘build as module’, ‘y’ means ‘build into the kernel’
CONFIG_R8188EU=m
CONFIG_88EU_AP_MODE=y

This however will differ depending on the Realtek chip in question and the build will fail with an indication which line in the kernel .config was not enabled when it should’ve been. Finally, if you do not intend to debug your product later on, make sure to build only the regular kernel (without the debug kernel), as that takes quite some time.