Re: [RFC 00/12] RFC: Devicetree-ACPI hybrid mode

[Bryan O'Donoghue <bod@kernel.org>]

On 26/06/2026 15:33, Bryan O'Donoghue wrote:
> On 23/06/2026 15:52, Hans de Goede wrote:
>> Comments, thoughts ?
> 
> Throw out DT and just do this...
> 
> One thing I like about this approach TBH is that you don't do the easy
> thing of presuming to push the hard work into the bootloader - thus
> creating a dependency on bootloader.
> 
> We've had _alot_ of problems doing DT selectivity to get OSes installed
> on arm64 laptops. You mentioned I2C-HID devices and EC controllers which
> I agree are a good and obvious targets.
> 
> I don't think this can replace a full and complete DT but, then I don't
> think that should be the objective.
> 
> Much like installing cursed OSes like Windows on "normal" laptops or x86
> machines, you'd expect to boot in ACPI mode have enough of the OS
> running to install more of the OS - which I think _can_ be a viable
> objective with an ACPI-DT translator.
> 
> Sadly OpenBSD could boot all the way to console on the Qcom laptops
> where Linux could not - because ACPI support was better there.
> 
> And, we have Nvidia laptops coming too, Windows laptops which will parse
> ACPI tables to boot.
> 
> There's almost no upside in having ACPI data and not trying to make
> maximal use of it, especially if you don't have a DT supplied by
> antecedent boot stages.
> 
> ---
> bod
> 

I'm going to agree with myself some more on the boot story.

If you can boot Linux _at_all_ and dump out ACPI tables from the booted 
system you are way further along than not being able to boot without a 
"real" DT.

Again, bootloaders have had to be educated on how to make that DT 
selection - a problem that isn't well solved or converged on - and even 
if such an agreed method were present, exactly 100% useless to you 
without the DT to go with it.

As a Linux user I don't expect everything to work, especially so on 
aarch64 but, if I can get to a boot console with a screen and keyboard - 
I have scope to play in a way I otherwise don't - parsing DSDT from 
Windows and walking backwards to DT.

DT _should_ be the landing zone of course but, ACPI-DT hybrid to "just 
boot" seems like an obvious yes to me.

---
bod