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authorBob Moore <robert.moore@intel.com>2012-08-17 13:07:54 +0800
committerLen Brown <len.brown@intel.com>2012-09-21 00:26:17 -0400
commitbe030a576854238250d70135644cde6a0ba34b0d (patch)
treea7521a65df5e117ef6aec3fcaa8160be7596a495 /include/acpi/actbl1.h
parent4e2f9c278ad84196991fcf6f6646a3e15967fe90 (diff)
downloadvexpress-lsk-be030a576854238250d70135644cde6a0ba34b0d.tar.gz
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>
Diffstat (limited to 'include/acpi/actbl1.h')
-rw-r--r--include/acpi/actbl1.h12
1 files changed, 9 insertions, 3 deletions
diff --git a/include/acpi/actbl1.h b/include/acpi/actbl1.h
index 300d14e7c5d..c41d6f96ed7 100644
--- a/include/acpi/actbl1.h
+++ b/include/acpi/actbl1.h
@@ -79,9 +79,15 @@
#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
*/
/*******************************************************************************