Re: [Libreboot] Operating System for Asus C201

[Paul Kocialkowski]

Hey there, I'll respond to the various concerns and questions raised in this
thread, in no particular order. First off, I'm glad to see such interest for the
C201 Libreboot port!

At this point, there are no distributions following the GNU Free System
Distribution Guidelines (GNU FSDG) that support the C201 out of the box. The
first problem is that it's an ARM machine, and most GNU FSDG-compliant
distributions don't support ARM. Only Parabola has ARM support at this point.
Some work would be needed to write up instructions regarding how to install
Parabola on the C201. This is something I have been meaning to do, but couldn't
find the time to do it yet. However, writing instructions is not all that is
required. The device needs a kernel with specific drives for its hardware, that
are not integrated into Linus Torvald's version of Linux, the upstream Linux
kernel.

Instead, CrOS systems use a downstream version of Linux, with changes for
hardware support. The source code for it is available as part of the ChromiumOS
project and it can be rebuilt from source. Until the upstream kernel is ready,
this downstream kernel is the best candidate to get a working free system on the
device.

One might be concerned about what comes with it, since it is a modified version
of the upstream kernel. I am not aware of any addition that would conflict with
users' privacy and security, but I have not checked extensively. Note that the
firmwares for Wi-Fi are not part of the kernel, but are out of the tree, as far
as I recall. Thus, this kernel could be deblobbed and packaged in Parabola, to
make the installation easier.

Note that the kernel must be wrapped in a particular image format for the
Depthcharge payload. This is to allow signature verification, a crucial security
feature. I do not intend to support anything else than Depthcharge in Libreboot
at this point. Actually, I think it is quite elegant and gets the job done
nicely.

Regarding my own setup, I have been using the device with Fedora since Debian
doesn't ship with llvmpipe (required for decent CPU-based graphics
acceleration). Either way, once the kernel is ready, any GNU/Linux system that
has ARM support can be used on the device, with little adaptation needed in
userspace. I will write up instructions for these systems too, probably on my
personal blog.

I am not using the internal Wi-Fi chip, that requires a proprietary firmware,
but use an ath9k_htc USB dongle instead. I enabled that module when building the
kernel and it works normally.

Aside from documenting the installation of GNU FSDG-approved systems and others
and improving the state of the Libreboot port (especially regarding the support
of security features), I'd also like to contribute to C201 support to the
upstream Linux kernel. Alas, Libreboot is not the only project I'm contributing
to, far from it, and all of that takes time, especially when it all happens on
spare time.

Cheers!
-- 
Paul Kocialkowski, low-level free software developer on embedded devices

Website: https://www.paulk.fr/
Coding blog: https://code.paulk.fr/
Git repositories: https://git.paulk.fr/ https://git.code.paulk.fr/

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