Allow values to be read from ACPI tables using the syntax
${acpi/<signature>.<index>.0.<offset>.<length>}
where <signature> is the ACPI table signature as a 32-bit hexadecimal
number (e.g. 0x41504093 for the 'APIC' signature on the MADT), <index>
is the index into the array of tables matching this signature,
<offset> is the byte offset within the table, and <length> is the
field length in bytes.
Numeric values are returned in reverse byte order, since ACPI numeric
values are usually little-endian.
For example:
${acpi/0x41504943.0.0.0.0} - entire MADT table in raw hex
${acpi/0x41504943.0.0.0x0a.6:string} - MADT table OEM ID
${acpi/0x41504943.0.0.0x24.4:uint32} - local APIC address
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown