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How do I shot Servo
-------------------

This set of tools lets you use a Servo control board for Chromebooks in some
kind of vaguely automated fashion. After installing these and configuring for
your local boards, you should have access to the CPU UART as
/dev/google-servo/$devicename/cpu-uart, and the EC as
/dev/google-servo/$devicename/ec-uart, as well as having servod itself
listening for more complex commands on a predictable port.


hdctools
--------

In order to actually communicate with the servo, you'll need to have hdctools
installed somewhere we can see it. This is available at:
https://chromium.googlesource.com/chromiumos/third_party/hdctools

You'll need libftdi-dev, tidy, and python-setuptools.

make
sudo make install
python setup.py build
sudo python setup.py install
sudo python setup.py develop


Kernel module
-------------

Build and install this kernel module. Those of you who pay attention to the
source may notice that it, in fact, does nothing. This is just here so the
kernel will actually bind to it, which will trigger udev rules, which will in
turn trigger systemd to start servod. There might be a better way to do this.

Anyway, just build and install it.


udev rules
----------

This udev rule is blindingly simple. Install it to /etc/udev/rules.d/.


systemd
-------

As above, but /etc/systemd/system/.


servod configuration
--------------------

The configuration, in /etc/google-servo.conf takes the form:
localalias,serial,port,boardtype

The localalias is what gets aliased into /dev/google-servo/$devicename/*, e.g.
peach-pi-on-my-desk, peach-pi-over-there, big-one, blaze-two. You get the
picture. The serial number comes from /sys/devices/*/serial; I recommend
discovering this with:
udevadm info --attribute-walk --name /dev/usb/google-servoN
The immediate parent of that device shown, should have an ATTR{serial} entry
in the form of "123456-12345".

Port is the port number to bind to for dut-control to use later. boardtype is
an internal value used by servo to work out how to communicate with the target
device; see hdctools/servo/data/ for something resembling a list of possible
values.


servod wrapper
--------------

This fairly trivial wrapper runs out of systemd and creates the device links
for /dev/google-servo/$devicename/*. You'll need python-numpy, python-pexpect,
python-pyudev, python-serial, and python-usb to run it.


Putting it all together
-----------------------

Once you've done all this, servod should turn up whenever you plug your board
in, and disappear once you haven't. Brilliant.