acpi_drv / platform_drv support

[Christian Helmuth]

Hello Jörg,

On Wed, Feb 24, 2021 at 15:01:26 CET, Joerg-C. Boehme wrote:
> I have some question about the: acpi_drv and platform_drv.
> 
> In short:
> Is acpi_drv and platform_drv are only supporting hardware boards with PCIe ?

In general, no, we do not depend on PCIe directly. Nevertheless, I
admit that we do not test PCIe-less systems in any real-world
scenario.

> And start the var/run/lighttpd.iso with qemu-system-x86_64 (without -machine
> q35 parameter!)
> qemu-system-x86_64 -no-kvm -display sdl -cpu core2duo -nographic -netdev
> user,id=net0,hostfwd=tcp::5555-:80,hostfwd=tcp::5556-:443 -net
> nic,model=e1000,netdev=net0 -serial mon:stdio -m 512 -cdrom
> var/run/lighttpd.iso

As you discovered this is not supported. The reason is not the missing
PCIe capability but that Qemu's i440FX chipset does not support
ECAM/MMCONF (memory-mapped) PCI configuration space access. We
replaced the I/O port based PCI driver implementation by MMCONF based
access after a vivid discussion in 2018 [1]. Thus, we may indirectly
depend on PCIe if systems lacking PCIe ports also lack MMCONF.

> * Can I somehow "manuel" configure the system on 440FX based hardware ?

In theory, you could generate the acpi_drv report by hand. But that's
not my playground.

> * Is there a reason why platform_drv is not supporting older hardware ?

We switched to MMCONF because of demand from the community and the
promise that it's widely available. We never considered to support
both PCI-config access options for complexity and testing effort
reasons.

[1] https://github.com/genodelabs/genode/commit/47724c68c2c27a430e9a60c55ebb42f8d4ebf941

Greets
-- 
Christian Helmuth
Genode Labs

https://www.genode-labs.com/ · https://genode.org/
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