On 01/29/2015 01:34 PM, Timur Tabi wrote:

On 01/29/2015 12:28 PM, Ard Biesheuvel wrote:

quoted

The UEFI stub in the kernel uses the DTB file format (FDT) to pass
information about the UEFI memory map and system table to the kernel.
It does so even if there is no device tree that describes the
platform. In this case, the file only contains a /chosen DT node, and
nothing else, and it is up to the kernel to figure out that it can ask
UEFI for a set of ACPI tables that it can use instead to configure the
system. Otherwise, the /chosen node properties are added to a device
tree that contains the full platform description.

The problem is that we have to decide how to distinguish a
conventional device tree DTB from a DTB that only exists to
communicate the UEFI entry points.

Ah, that's exactly what I'm seeing.  The UEFI stub in our kernel 
generates a DTB, and therefore I always need to put acpi=force on our 
kernel command line.

I expect some of the distros to patch ACPI always enabled. So from my
point of view this affects only those wanting to follow upstream.

Jon.