diff options
| author | Bob Moore <robert.moore@intel.com> | 2012-08-17 13:07:54 +0800 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2012-09-21 00:26:17 -0400 |
| commit | be030a576854238250d70135644cde6a0ba34b0d (patch) | |
| tree | a7521a65df5e117ef6aec3fcaa8160be7596a495 /include/acpi/actbl3.h | |
| parent | 4e2f9c278ad84196991fcf6f6646a3e15967fe90 (diff) | |
| download | lwn-be030a576854238250d70135644cde6a0ba34b0d.tar.gz lwn-be030a576854238250d70135644cde6a0ba34b0d.zip | |
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/actbl3.h')
| -rw-r--r-- | include/acpi/actbl3.h | 12 |
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 */ /******************************************************************************* |