i2c on RPi Zero?

[Oleksandr Tymoshenko]

Per Hedeland (per at hedeland.org) wrote:
> I did a bit more testing on the Zero to see if the FreeBSD version
> mattered:
> 
> FreeBSD-12.0-STABLE-arm-armv6-RPI-B-20190103-r342709.img - still no
> luck.
> 
> FreeBSD-11.2-STABLE-arm-armv6-RPI-B-20190103-r342709.img - works!
> (I.e. dmesg reports as below and /dev/iic{0,1} get created - I haven't
> tested actual usage beyond having 'i2c -s' report "no devices found".)
> 
> I guess that the i2c support hasn't been removed intentionally,
> i.e. this seems to be a regression - or is there some additional
> config etc required to enable it with FreeBSD-12? The iic and iicbus
> drivers appear to be built into the kernel in both 11 and 12.
> 
> (I haven't tested FreeBSD-12 on the Pi B, but I would guess that the
> result will be the same as on the Zero, since it seems the hardware is
> the same.)

There was a transition in device tree files between 11 and 12.
bcm2708-rpi-0-w.dtb has i2c nodes but they're disabled by default.
Try editing config.txt on FAT partition and adding following line:

dtparam=i2c

This should make boot firmware to enable device nodes in the device
tree blob during the boot.

-- 
gonzo