Question about FADT length

[Hanjun Guo <hanjun.guo@linaro.org>]

Hi,

I ran into some compile errors when I was prototyping the code
for the proposals in ASWG, it turns out that some field in FADT is
changed and "reserved4[0]" used in ACPI_FADT_V2_SIZE will
cause the error.

So my question is that the length of very version of FADT is
fixed, why not use a constant value for this puspose?

Here is the code:

/*
  * Sizes of the various flavors of FADT. We need to look closely
  * at the FADT length because the version number essentially tells
  * us nothing because of many BIOS bugs where the version does not
  * match the expected length. In other words, the length of the
  * FADT is the bottom line as to what the version really is.
  *
  * For reference, the values below are as follows:
  *     FADT V1  size: 0x074
  *     FADT V2  size: 0x084
  *     FADT V3  size: 0x0F4
  *     FADT V4  size: 0x0F4
  *     FADT V5  size: 0x10C
  */
#define ACPI_FADT_V1_SIZE       (u32) (ACPI_FADT_OFFSET (flags) + 4)
#define ACPI_FADT_V2_SIZE       (u32) (ACPI_FADT_OFFSET (reserved4[0]) + 3)
#define ACPI_FADT_V3_SIZE       (u32) (ACPI_FADT_OFFSET (sleep_control))
#define ACPI_FADT_V5_SIZE       (u32) (sizeof (struct acpi_table_fadt))

Why not  #define ACPI_FADT_V1_SIZE 0x074 ?
Did I miss something? any clarify will be appreciated :)

Thanks
Hanjun