K 10
svn:author
V 6
grembo
K 8
svn:date
V 27
2016-05-30T09:05:24.806010Z
K 7
svn:log
V 579
Fix ig4 operation for certain machines

Some machine BIOSes use the I2C bus and leave it in a state that causes
interrupts to not work properly due to a pending interrupt having been
latched.

Refactor the code a bit to clear pending interrupts when I2C is enabled.
This fixes the primary problem.

Also fix a possible race condition in the interrupt handler where the
interrupt was being cleared after reading the status instead of before.

Reported by:	pfg
Reviewed by:	jhb
Approved by:	jhb
Obtained from:	DragonFly BSD
Differential Revision:	https://reviews.freebsd.org/D6586

END