ichwd: option to globally disable SMI

[Poul-Henning Kamp]

In message <49DA1173.1080606 at icyb.net.ua>, Andriy Gapon writes:

>I am attaching a patch that makes ichwd check and report result of SMI bit
>operations and also try to disable SMI globally if permitted by
>hw.ichwd.use_global_smi tunable.

Disabling SMI globally is incredibly ill-advised, for one thing it
may cause your laptop to autowarnerize, but it can also ruin your
batteries, prevent ACPI from working etc.

Under no circumstances should FreeBSD attempt to disable SMI globally
without explicit instruction from a knowledgeable and informed user.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.