[Dev] [Libreboot] Operating System for Asus C201

[Denis 'GNUtoo' Carikli]

Hi,

On Sun, 17 Apr 2016 14:23:18 +0100
Mike <mike at mjbuckingham.co.uk> wrote:

> I am now at the stage of installing an operating system on to the
> laptop and have a few questions that I would very much appreciate
> some help with before I begin:
Parabola has been ported to ARM.

I think it's much easier if you don't use device specific kernels, but
instead uses the mainline one.

If you have an x86 parabola install, you can easily bootstrap(with
pacstrap) an ARM installation from it.

The ARM version has mainline Linux.
With the linux-libre package, the image is in: /boot/vmlinuz-linux-libre

However you also need to load a dtb
from /boot/dtbs/linux-libre/rk3288-veyron-*.dtb
Unfortunately, I don't remember which one of theses is for the C201.

Background information:
-----------------------
On ARM, Linux now uses the devicetree to describe hardware.
It will describe all hardware that cannot be auto-detected such as the
CPU,
the serial ports etc. This is machine specific.

To boot, you need to load the Linux Image and the dtb file.

If your bootloader supports it (here it's part of libreboot) you should
use it to load both, else you have something called dtb-append in Linux.

dtb-append:
-----------
To use that, just add the dtb at the end of the zImage like that:
$ cat /boot/vmlinuz-linux-libre \
  /boot/dtbs/linux-libre/rk3288-veyron-<yourboard>.dtb \
  > /boot/zImage-appended.bin

This will produce a zImage-appended.bin that has the dtb.

Chromebook specific:
--------------------
The main difficulty here will be to make depthcharge (the libreboot
payload) load that zImage (and dtb).

With the stock boot firmware, the kernel has to be signed with a key to
be loaded by depthcharge.

Unfortunately I don't remember how the default boot fimrware and
libreboot differ with their security models, and I don't have a
chromebook to check.

Denis.
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