RE: HT not working by default since 2.4.22

[Brown, Len]

> Now that I've thought of it (aren't I humble), I rather like 
> CONFIG_HT.
> It's simple and it's effects should be obvious to both developer and
> user:
> 
> 	CONFIG_HT, CONFIG_ACPI == ACPI
> 	!CONFIG_HT, CONFIG_ACPI == ACPI
> 	CONFIG_HT, !CONFIG_ACPI == HT-only ACPI
> 	!CONFIG_HT, !CONFIG_ACPI == no ACPI
> 
> Following the "autoconf model", what we really want to be testing with
> CONFIG_xxx is _features_, where possible. "hyperthreading: yes/no" is
> IMO more clear than "do I want ht-only ACPI or full ACPI", 
> while at the
> same time being more fine-grained and future-proof.

I like positive logic too.
I went so far as to try to implement this back when I deleted "noht".

The problem is that "!CONFIG_HT" is meaningless.  It implies that
you can have CONFIG_ACPI but still "config-out" HT, which you can't.

Ie. The 2nd row above says to give me ACPI w/o HT.
If you delete that row and reverse the polarity you get:

!CONFIG_ACPI_HT_ONLY, CONFIG_ACPI == ACPI
CONFIG_ACPI_HT_ONLY, !CONFIG_ACPI == HT-only ACPI
!CONFIG_ACPI_HT_ONLY, !CONFIG_ACPI == no ACPI

Here we can use config to emphasize that it is not possible to select
CONFIG_ACPI and CONFIG_ACPI_HT_ONLY at the same time.

Cheers,
-Len

Ps. Note that in 2.6 CONFIG_X86_HT exists and covers the sibling code.
It depends on CONFIG_SMP, and CONFIG_ACPI_HT_ONLY depends on it. (in the
ACPI patch)
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