MFC r330304: imcsmb(4): Intel integrated Memory Controller (iMC) SMBus

MFC r330304: imcsmb(4): Intel integrated Memory Controller (iMC) SMBus
controller driver

imcsmb(4) provides smbus(4) support for the SMBus controller functionality
in the integrated Memory Controllers (iMCs) embedded in Intel Sandybridge-
Xeon, Ivybridge-Xeon, Haswell-Xeon, and Broadwell-Xeon CPUs. Each CPU
implements one or more iMCs, depending on the number of cores; each iMC
implements two SMBus controllers (iMC-SMBs).

*** IMPORTANT NOTE ***
Because motherboard firmware or the BMC might try to use the iMC-SMBs for
monitoring DIMM temperatures and/or managing an NVDIMM, the driver might
need to temporarily disable those functions, or take a hardware interlock,
before using the iMC-SMBs. Details on how to do this may vary from board to
board, and the procedure may be proprietary. It is strongly suggested that
anyone wishing to use this driver contact their motherboard vendor, and
modify the driver as described in the manual page and in the driver itself.
(For what it's worth, the driver as-is has been tested on various SuperMicro
motherboards.)

git-svn-id: svn://svn.freebsd.org/base/stable/10@330680 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f