Stephen,

> The Linux API seems to expose what you need. See:
> https://www.kernel.org/doc/html/v4.14/driver-api/i2c.html

Thank you.

> That was after a few minutes Googling.

I have been googeling for quite a bit longer than that, but just have not
been able to come up with the right keywords. :-\

> That was the easy bit. However, you don't say what cable lengths
> or electrical environment you will be working with.

Thats because I regard that as a fully seperate item, having nothing to do
with the "One I2C bus, two programs" one problem.  One thing(/problem) at a
time seems to work best for me.

Also, what I currently have (in experimental wiring to at least two devices)
does not seem to cause any problems (yet).

> On test, it failed (but recovered) more than once per hour. On
> reverting to the bit-banged driver we had already supplied, they
> saw no failures in more than two weeks.

Ever found out what the problem was ?  A too-high transmission speed ?

> If you want to use an unsupported device

???   Unsupported ?    I was not aware that there where supported devices.

I normally grab myself the devices datasheet and work my way up from there.
Much more fun than just installing someone elses drivers. :-)

> I suggest you do it from scratch, mmap() the GPIO port, and
> read/wite the pins yourself

Currently I've just been using the available drivers, but with me being me
there is a rather good chance (understatement) that I will try my hand at
that too.

Regards,
Rudy Wieser

--- SoupGate-Win32 v1.05