[request for testing] isl, cyapa on chromebooks

If you have a Chromebook where you are currently able to use isl and cyapa
drivers, could you please test the following code change?
https://people.freebsd.org/~avg/ig4-i2c.diff

The change moves the drivers from the SMBus to the I2C bus and as such some
configuration changes are required.
Namely, you will now need iicbus driver either in the kernel configuration or as
a module.  For now the smbus driver is also required.
You also need to add some entries to /boot/device.hints:
hint.isl.0.at="iicbus0"
hint.isl.0.addr=0x88
hint.isl.1.at="iicbus1"
hint.isl.1.addr=0x88
hint.cyapa.0.at="iicbus0"
hint.cyapa.0.addr=0xce
hint.cyapa.1.at="iicbus1"
hint.cyapa.1.addr=0xce

The hints are required because auto-probing (either via the bus enumeration or
self-identification) is disabled for now for safety reason.
Also, as I understand, the Intel chipset used in the supported Chromebooks
provides to i2c buses (possibly in addition in an smbus) and I am not sure on
which of the i2c buses the devices reside.

The changes are build tested only, because I do not have access to the hardware.
So, kernel panics, etc are not unexpected.

Please let me know if drivers attach at all and if there are any issues with them.
A verbose dmesg would be of great help.  That could be obtained by booting in a
verbose mode if the drivers are auto-loaded or by setting debug.bootverbose=1
before loading the drivers if that's done manually.

Please also note that ig4 driver is changed, so it too has to be rebuilt if you
are going to build individual modules rather than do a kernel + modules build.

I will appreciate your testing and feedback.
Thank you!
-- 
Andriy Gapon