ACPICA: Add support for complex _PLD buffers.

_PLD (Physical Location of Device) returns a bit-packed buffer that
is difficult to parse. This change adds a new interface,
AcpiDecodePldBuffer that parses the buffer into a more usable
local struct. Also adds macros to both get and set individual
fields within the packed _PLD buffer. Adds a new include file,
acbuffer.h - which will be expanded to add structs for other
ACPI names that return buffers. ACPICA BZ 954.

Emit (in comments) the decoded contents of a static _PLD buffer
in order to improve comprehension of this bit-packed buffer.

Add multi-endian support to the _PLD decode routine. Deploy the
multi-endian macros to extract data from the _PLD buffer.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/include/acpi/actbl3.h b/include/acpi/actbl3.h
index 37781ab806a5..8c61b5fe42a4 100644
--- a/include/acpi/actbl3.h
+++ b/include/acpi/actbl3.h
@@ -86,9 +86,15 @@
 #pragma pack(1)
 
 /*
- * Note about bitfields: The u8 type is used for bitfields in ACPI tables.
- * This is the only type that is even remotely portable. Anything else is not
- * portable, so do not use any other bitfield types.
+ * Note: C bitfields are not used for this reason:
+ *
+ * "Bitfields are great and easy to read, but unfortunately the C language
+ * does not specify the layout of bitfields in memory, which means they are
+ * essentially useless for dealing with packed data in on-disk formats or
+ * binary wire protocols." (Or ACPI tables and buffers.) "If you ask me,
+ * this decision was a design error in C. Ritchie could have picked an order
+ * and stuck with it." Norman Ramsey.
+ * See http://stackoverflow.com/a/1053662/41661
  */
 
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