On Tue, Mar 1, 2016 at 9:36 AM, Toshi Kani <toshi.kani@xxxxxxx> 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 > spec. 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? -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
