7fd3982ad957c796758a90e2988401a884241
author Zhao Yakui <yakui.zhao@intel.com> 1187943496 +0800
committer Len Brown <len.brown@intel.com> 1187995585 -0400

ACPI: Validate XSDT, use RSDT if XSDT fails

ACPI 1.0 used an RSDT with 32-bit physical addresses.
ACPI 2.0 adds an XSDT with 32-bit physical addresses.
An ACPI 2.0 aware OS is supposed to use the XSDT
(when present) instead of the RSDT.

However, several systems have failed because the XSDT
contains NULL entries -- while it is missing pointers
to needed tables, such as SSDTs.

When we find an XSDT with NULL entries, discard it
and use the ACPI 1.0 RSDT instead.

http://bugzilla.kernel.org/show_bug.cgi?id=8630

Signed-off-by: Zhao Yakui  <yakui.zhao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>