Some function keys not working on a ThinkPad W550s

[Celejar <celejar@gmail.com>]

Hi,

I recently installed Debian Jessie on a ThinkPad W550s. It's a pretty
standard installation, beginning with a fairly minimal package set,
then adding Xfce and a bunch of other stuff, including some Gnome / GTK
applications and a few things from backports. I'm currently running
kernel 4.7.0-0.bpo.1-amd64 from backports.

Some of the function keys work (e.g., Fn-F5/F6 for brightness down/up),
but some do not (e.g., F1-F3 for volume control, and F4 for suspend
(suspend works fine out of the box via the Xfce suspend hooks)). Any
idea how to fix / troubleshoot this?

I saw this:

http://www.thinkwiki.org/wiki/How_to_get_special_keys_to_work

But the details are really not explained well - what are these masks,
what do they mean, and where are they documented?

I'm coming from a T61, where the function keys, at least all the ones I
tried and needed, seemed to work fine, even out of the box, as far as I
can recall.

Celejar