Re: [PATCH v4 00/13] Add ACPI _DSD and unified device properties support

From: David Woodhouse
Date: Wed Oct 15 2014 - 11:12:58 EST

> We have been checking for all DT platforms, and that's a bug for DT.
> Copying that bug to ACPI is inexcusable given we know it's a bug to do
> so.

We'll, perhaps it should be named 'used-by-firmware' and actually it's
just as valid under ACPI as it is on RTAS systems. All it does is stop the
OS from using the port.

> I understand that. However, where a binding doesn't make sense (as in
> this case), it shouldn't be enabled for ACPI as it provides a larger
> surface area for misuse, for no benefit.

These are *optional* properties. They were optional precisely *because*
they only make sense in some cases. I don't know that it makes sense to
take them away. The benefit we get is *consistency*. For example if
someone *does* use the property in question as 'used-by-firmware' and
expects the OS not to touch it, we don't want that to change behaviour
between ACPI and fdt boots.


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