Device file shows open in lsof, but not opened in strace

Hi, all! I have a short, specific question, and a broader more
general question.

Some background: I'm trying to understand the workings of a device
with a proprietary binary driver. I have access to a binary-only
program which I believe communicates with the device, most likely
through /dev/buttons.

The short specific question: When I run

% lsof | grep program

I get a listing of files that the program has open, which includes
this entry:

program 921 root 15u CHR 222,0 331 /dev/
buttons

However, if I run

% killall program
% strace -o output.log program &

and let the program run, there is no mention of /dev/buttons in
output.log. No open statement at all.

So, how does a program open a file without the open() statement (or
any other record) being produced in strace?

The longer, more general question: I believe that the program may be
communicating with the driver through ioctrls. Is there a way to
moniter these, or otherwise find out what exactly is going on? At
this point, I'd be happy to find ANY evidence of actual communication
between the program and the device.

Comments, suggestions, questions? Thanks very much in advance!

-John

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