Arch Linux

udlfb interferes with the normal loading of udl, reducing the usefulness of USB 2.0 DisplayLink devices as the udlfb driver prevents using them as plug-and-play monitor adapters on systems that don't already have udlfb blacklisted.

I wasn't sure if udlfb provided some extra functionality or not, so I asked about it on the dri-devel mailing list:

> - Why are there two drivers for these devices (udl and udlfb)? Would
> it be possible to merge all the functionality into udl so I don't have
> to blacklist udlfb on every computer I want to use these adapters
> with?

I got the following responses:

> Distro problem, ask them not to enable udlfb, udl should cover them all.

> We have a bunch of other such cases, the solution is to just not compile
> _any_ of the fbdev drivers. You still need fbdev itself, plus fbcon, for
> the kernel console, but the fbdev drivers should all be drm drivers which
> provide fbdev support through the fbdev emulation layer we have.
>
> If your distro enables udlfb, your distro is doing it wrong.

So the consensus upstream seems to be "disable udlfb, it's deprecated in favor of fbdev emulation on the udl drm driver".

Also, just to be sure that the udlfb wasn't enabled for any particular purpose, I checked the git blame of the kernel config--the option has been enabled there since the package was created in 2011, so it probably was enabled back when the udlfb driver was introduced and wasn't disabled after the udl drm driver was added.

tl;dr: Please un-set CONFIG_FB_UDL in the kernel config.