Re: Debian on Lenovo Chromebook (ARMv8)
On 07/04/2023 20:56, Brian Sammon wrote:
> On Wed, 5 Apr 2023 18:31:10 +0300 Alper Nebi Yasak
> <alpernebiyasak@gmail.com> wrote:
>> The SC7180 one? Does it work with the Debian-built kernel?
>
> It's a Qualcomm Snapdragon 7c Ver2. I'm running the kernel that came
> with the image I downloaded from
> https://github.com/hexdump0815/imagebuilder a few months ago. I
> believe it's a 5.19.1 kernel minimally patched from kernel.org
> sources (and possibly some customization of the .config and
> devicetree). Reportedly, v6 of the kernel should work unpatched. I
> should start a DebianOn page for the wiki.
Ah, OK. I want to eventually go through VelvetOS sources to see what we
need to enable for each device, but didn't have the time yet. (As a
start I have filed #1034159 based on ChromiumOS sources)
>> It's just how Google designed their bootloader to boot ChromeOS,
>> instead
>
> Right, I get the general idea. Just not sure if you need to follow
> that process 100%, or if there's some flexibility. In particular, I
> don't know if the lz4 step is necessary, and whether other
> compression formats are allowed.
It's a mess, depends on the board. For arm64, the kernel can either be
uncompressed, lz4 or lzma. There is a size limit for the final image
(e.g. 32MiB for RK3399 ones, 512MiB for Duet 5) so that can make it
necessary to compress things. Newer boards can have compressed dtb files
as well.
Even older, 32-bit arm boards have 8/16MiB limits, can't compress the
kernel (but it's already self-compressed) and don't properly support
initramfs in FIT. x86 ones don't use FIT, just the kernel "bzImage" not
even meant to have an initramfs. (Insane hacks needed but possible to
use initramfs in both).
Also, AFAIK you can use your own keys for vbutil_kernel and make the
firmware specifically check for them in verified mode, but that takes
some work.
> Relatedly, I'm wondering how many kernel partitions I can have. Can
> I have (usefully) a "KERN-Z" partition?
I don't know if there's a hard limit, but the "priority" flag can only
be in a 0-15 range. In daily use, having two partitions will let you do
A/B upgrades and safe rollbacks, but having more than two doesn't seem
to add much value.
> Is there anywhere (besides this list) that I should be
> reading/subscribed to to learn more about debian-installer support
> for Chromebooks?
Installer discussion in general happens at the debian-boot@ list and
#debian-boot IRC channel. I'm not exactly talkative while I work, though
I'm bound to announce things there eventually. If you want a general
overview of things, I had a talk at DebConf22 [1], but it's somewhat
outdated as things progressed.
[1] Solving "How Can I Run Debian on My Chromebook?" For Good
https://debconf22.debconf.org/talks/87-solving-how-can-i-run-debian-on-my-chromebook-for-good/
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