ASUS Chromebook C201

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This is a Chromebook, using the Rockchip RK3288 SoC. It uses an ARM CPU, and has free EC firmware (unlike some other laptops). More RK3288-based laptops will be added to libreboot at a later date.

Flashing instructions can be found at ../install/#flashrom

Google’s intent with CrOS devices

CrOS (Chromium OS/Chrome OS) devices, such as Chromebooks, were not designed with the intent of bringing more freedom to users. However, they run with a lot of free software at the boot software and embedded controller levels, since free software gives Google enough flexibility to optimize various aspects such as boot time and most importantly, to implement the CrOS security system, that involves various aspects of the software. Google does hire a lot of Coreboot developers, who are generally friendly to the free software movement and try to be good members of the free software community, by contributing code back.

CrOS devices are designed (from the factory) to actually coax the user into using proprietary web services (SaaSS) that invade the user’s privacy (ChromeOS is literally just the Google Chrome browser when you boot up, itself proprietary and comes with proprietary add-ons like flash. It’s only intended for SaaSS, not actual, real computing). Google is even a member of the PRISM program, as outlined by Edward Snowden. See notes about ChromeOS below. The libreboot project recommends that the user replace the default ChromeOS with a distribution that can be used in freedom, without invading the user’s privacy.

We also use a similar argument for the MacBook and the ThinkPads that are supported in libreboot. Those laptops are supported, in spite of Apple and Lenovo, companies which are actually hostile to the free software movement.

Considerations about ChromeOS and free operating systems

This laptop comes preinstalled (from the factory) with Google ChromeOS. This is a GNU+Linux distribution, but it’s not general purpose and it comes with proprietary software. It’s designed for SaaSS. Libreboot recommends that users of this laptop replace it with another distribution.

Debian GNU+Linux

https://wiki.debian.org/InstallingDebianOn/Asus/C201 shows how to install Debian.

Devuan GNU+Linux

https://notabug.org/dimkr/devsus produces bootable and installable Devuan images.

Parabola GNU+Linux

See: https://lists.gnu.org/archive/html/libreboot/2015-12/msg00026.html

In this discussion thread (on the old GNU Libreboot mailing lists), there are instructions for installing Parabola on C201 and other rockchip chromebooks supported by Libreboot.

Caution: Video acceleration requires a non-free blob, software rendering can be used instead.

The C201 has a Mali T GPU, which requires a non-free blob. A driver, Tamil, was written, but its source code has not been released. The developer has so-far withheld it. Use software rendering to avoid the blob instead. Most tasks can still be performed without video acceleration, without any noticeable performance penalty.

In practise, this means that certain things like games, blender and GNOME shell (or other fancy desktops) won’t work well. The libreboot project recommends a lightweight desktop which does not need video acceleration, such as XFCE or LXDE.

As it is unlikely that Tamil will be released, the chai project is writing a driver as well. Ask on IRC if you think you can contribute.

Caution: WiFi requires a non-free blob, a USB dongle can be used instead.

These laptops have non-removeable (soldered on) WiFi chips, which require non-free firmware in the Linux kernel in order to work.

The libreboot project recommends using an external USB wifi dongle that works with free software. See #recommended_wifi.

There are 2 companies (endorsed by Free Software Foundation, under their Respects your Freedom guidelines), that sell USB WiFi dongles guaranteed to work with free software (i.e. linux-libre kernel):

These wifi dongles use the AR9271 (atheros) chipset, supported by the free ath9k_htc driver in the Linux kernel. They work in linux-libre too.

EC firmware is free software!

It’s free software. Google provides the source. Build scripts will be added later, with EC sources provided in libreboot, and builds of the EC firmware.

This is unlike the other current libreboot laptops (Intel based). In practise, you can (if you do without the video/wifi blobs, and replace ChromeOS with a distribution that respects your freedom) be more free when using one of these laptops.

The libreboot FAQ briefly describes what an EC is: ../../faq.html#firmware-ec

No microcode!

Unlike x86 (e.g. Intel/AMD) CPUs, ARM CPUs do not use microcode, not even built in. On the Intel/AMD based libreboot systems, there is still microcode in the CPU (not considered problematic by the FSF, provided that it is reasonably trusted to not be malicious, since it’s part of the hardware and read-only), but we exclude microcode updates (volatile updates which are uploaded at boot time by the boot firmware, if present), which are proprietary software.

On ARM CPUs, the instruction set is implemented in circuitry, without microcode.

Depthcharge payload

These systems do not use the GRUB payload. Instead, they use a payload called depthcharge, which is common on CrOS devices. This is free software, maintained by Google.

Flash chip write protection: the screw

It’s next to the flash chip. Unscrew it, and the flash chip is read-write. Screw it back in, and the flash chip is read-only. It’s called the screw.

The screw is accessible by removing other screws and gently prying off the upper shell, where the flash chip and the screw are then directly accessible. User flashing from software is possible, without having to externally re-flash, but the flash chip is SPI (SOIC-8 form factor) so you can also externally re-flash if you want to. In practise, you only need to externally re-flash if you brick the laptop; read ../install/bbb_setup.html for an example of how to set up an SPI programmer.

Write protection is useful, because it prevents the firmware from being re-flashed by any malicious software that might become executed on your GNU+Linux system, as root. In other words, it can prevent a firmware-level evil maid attack. It’s possible to write protect on all current libreboot systems, but CrOS devices make it easy. The screw is such a stupidly simple idea, which all designs should implement.

Copyright © 2015, 2017 Leah Rowe info@minifree.org
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License Version 1.3 or any later version published by the Free Software Foundation with no Invariant Sections, no Front Cover Texts, and no Back Cover Texts. A copy of this license is found in ../fdl-1.3.html

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