I’ve been poking around the ‘newer’ AMW0 DSDT implementation (I’ll call it AMW0 v2), and I think I’ve worked it out now. Basically, rather than being an extension of the old AMW0 (we’ll name this ‘AMW0 v1′ to be original), it’s actually a backwards compatible addition of WMID to AMW0 – it has all the methods from both (plus an extra method to return a binary MOF), so can be treated as either.

So, for background – acerhk worked by making 32 bit BIOS calls. These calls take four arguments, each 4 bytes long, to give a total of 16 bytes.

AMW0 v1 just shifts the call into a method in WMI ACPI – we use the same arguments, but the call is done in ACPI, so we don’t have to care about poking into the BIOS, or whether this is a 32 or 64 bit system.

WMID implemented a ’simple’ method, so rather than needing to know the exact arguments for the BIOS, we just give the relevant method ID (and for writing, also the value), and then call that.

AMW0 v2 implements all the old AMW0 v1 methods, so is completely backwards compatible. However, since it also implements all of the WMID interface, it should be possible to update acer_acpi to use the WMID methods instead on these laptops, since it means we don’t need EC data for reading wireless and bluetooth (with the added advantage that we can control the mail LED through the ‘old’ AMW0 v1 methods).

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