[Devel] Field Offset constraints

[Patrick Georgi <pgeorgi at google.com>]

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Hi everybody,

at coreboot[1] we use iasl to compile static ASL for various hardware.
Recent versions of iasl emit a notice for redundant Offset statements in
Fields, apparently with the expectation that they shouldn't exist.

This poses a problem for us since we're sometimes using Offset as a guard,
making sure that we didn't inadvertedly shifted fields around (too much),
with the expectation that these were redundant in the "good" case.

Since that operator wasn't really suited for that purpose anyway, and now
throws warnings (which we try to avoid in our builds), are there plans to
add some keyword for compile time constraints checks, or any objections to
having such a feature (should one of us decide to implement it)?

Maybe something like

Field (NAME, ByteAcc, Lock, Preserve)
{
    Item(FIE1, 0, 0, 8)
    Item(FIE2, 1, 0, 8)
    Offset(0x10)
    Item(FIE3, 0x10, 0, 8)
}

in which Item(Name, Byte, Bit, Length) would compile to "Name, Length,"
inside a field after ensuring that the byte and bit offsets match the
current location.

Thoughts?

Thanks,
Patrick Georgi

[1] https://www.coreboot.org/
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