On Tue, Mar 1, 2016 at 9:36 AM, Toshi Kani <toshi.kani(a)hpe.com> wrote:
On Tue, 2016-03-01 at 16:03 +0000, Moore, Robert wrote:
> We have a bunch of macros in include/acmacros.h -- like this:
> ACPI_MOVE_16_TO_16(d, s)
There is a problem in using the ACPICA byte-swap macros. ACPI is little-
endian arch, so the macros are set to perform byte-swappings when the CPU
arch is big-endian. This case, however, is the other way around. The
fields in question are defined & stored as arrays of bytes. If you treat
them as multi-bytes numeric values, then you need to byte-swap them when
the CPU arch is little-endian because arrays of bytes have the same
addressing as big-endian.
Another issue is that it is not clear who needs to perform the byte-
swapping among ACPICA and drivers. If ACPICA, drivers must agree that
these fields are always treated as multi-bytes numeric values despite of
the spec. If drivers, we need to make sure that only a single driver
performs this byte-swapping one time as ACPI tables are global structures.
I think it is much clearer to define the structure according to the ACPI
I think the "ACPI tables are little-endian" assumption is pervasive
throughout the implementation.
Toshi, it seems all we need is conversions like:
- sprintf(buf, "%#x\n", dcr->vendor_id);
+ sprintf(buf, "%#x\n", le16_to_cpu(dcr->vendor_id));
...for the values exported to userspace through sysfs, but otherwise
leave the base table definitions as is. Will this suffice?