Re: [PATCH] ACPI: Implement overriding of arbitrary ACPI tables via initrd

Konrad Rzeszutek Wilk
2012-03-24T18:47:30Z

> 2. We create a new simple header (just a magic number, an identifier
> for the type of data, and a length) for each of the early-initrd
> objects:
>
> struct early_initrd_header {
> u64 magic; /* 0xa5a46ce422d8f5a1 */

Probably should also have:
u32 version;

in case we decide to expand this structure in the future, and:
> u32 type; /* 1 = file data, 2 = ACPI, 3 = microcode... */
> u32 length; /* Length of data object */
> };

and encapsulate the whole thing in a 4K union?

>
> XXX: Should we make this a defined endianness (presumably
> bigendian), or use host-endianness? I would guess the former might
> be better...

Perhaps the header should be in big-endian (that is the same as the network
byte order, right?) and each sub-type can define its own endian?

The sub-types could be:
struct microcode_type {
u64 magic;
u32 version;
#define BIG_ENDIAN 1<<1
#define LITTLE_ENDIAN 1<<2
u32 flags;
}

and that could be attached to the end of the 'early_initrd_header' ?

>
> Either of these allow one piece of code to quickly bypass bits that
> doesn't belong to it.
>
> Thoughts?
>
> -hpa
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