Comment by aseipp
4 hours ago
Someone from Qualcomm posted a "DT-ACPI Hybrid Mode" set of patches a while back that let you call ACPI table functions, etc even while booting with the device tree, allowing you to control some things like keyboard lightning/power management independently. That would be a good first step but I'm not sure it went anywhere in the meantime. In theory supporting Device Tree by including the blob in a ROM somewhere shouldn't be much more work (if any) than including working ACPI tables, but we all know how that works out in practice!
> supporting Device Tree by including the blob in a ROM somewhere shouldn't be much more work (if any) than including working ACPI tables, but we all know how that works out in practice!
This is definitely a thing in some embedded systems I’ve used. There are some Marvell boards which do this. They all use U-boot though.
The problem is that the content of the device tree isn't really stable -- if a new kernel version has a driver with a new required parameter for instance, suddenly your ROM device tree is out of date and much less useful.
Oh, that's a good point I forgot about; I suppose DT interfaces aren't considered part of the stability contract for users... Really Device Tree is somewhat "Linux-specific"-enough and low level enough that issues like this aren't ideal. But if we could just get to the point that was a problem, I'd be happier than now, I suspect!