docs: Add user and developer documentation about Chamelium support

This introduces plain-text documentation about the Chamelium aimed at
users who wish to deploy the platform, as well as developers who wish
to work on improving IGT support for it.

Given the contents of this documentation, it felt more relevant to make
it part of the tree instead of the API reference.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@linux.intel.com>
(with one small typo fixed)
Reviewed-by: Lyude Paul <lyude@redhat.com>

1 files changed, 153 insertions, 0 deletions

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+Chamelium Support in IGT
+========================
+
+This document provides information, instructions and a tasks list for Chamelium
+support in IGT.
+
+Introduction
+------------
+
+The Chamelium is a platform that acts as a display monitor emulator. It provides
+advanced access and control over the various signals a display receives.
+
+As such, it allows testing display features that can otherwise not be tested in
+IGT without external hardware.
+
+The platform was developed by Google in order to test display and audio-related
+features of ChromeOS devices. It was initially developed internally by Google as
+part of the ChromeOS effort under the name Chameleon and was later made external
+as part of the ChromiumOS effort, under the name Chamelium.
+
+It consists of a custom-made display emulator board connected to an Arrow SoCKit
+via a flexible cable, with two DisplayPort connectors, one HDMI and one VGA.
+
+The SoCKit uses a Cyclone V SoC, with both a FPGA and an ARM CPU. While the FPGA
+is used for logic control, the CPU runs daemons that allow the board to be
+controlled over the network via a XMLRPC interface.
+
+Documentation
+-------------
+
+Documentation about the Chamelium is made available by Google through the
+ChromiumOS projet wiki: https://www.chromium.org/chromium-os/testing/chamelium
+
+Deploying the Chamelium With IGT
+--------------------------------
+
+Instructions from the ChromiumOS wiki detail how to setup the Chamelium:
+https://www.chromium.org/chromium-os/testing/chamelium#TOC-Setting-up-Chamelium
+
+The should be followed up until the "Setup your Linux host, DUT and the FPGA"
+section. At this point, IGT has to be configured to connect to the Chamelium.
+
+It may be necessary to give the Chamelium a static IP address, depending on
+the network setup. This can be configured (via the serial console) by editing
+the Debian-styled /etc/network/interfaces configuration file.
+
+Chamelium support requires setting up dedicated IGT configuration, as explained
+in the Core and Chamelium parts of the IGT API Reference in the documentation.
+
+Note that running the chamelium tests with the Chamelium configuration deployed
+and the Chamelium disconnected or unreachable will result in network timeouts
+that take seconds. It is thus preferable (especially in the case of an automated
+CI system with a shared testlist) to remove the Chamelium configuration from the
+hosts that shouldn't connect to the Chamelium so that they can be skipped, which
+is faster than a network timeout.
+
+An example fully-featured configuration follows:
+[Common]
+FrameDumpPath=/root/
+
+[Chamelium]
+URL=http://192.168.72.1:9992
+
+[Chamelium:DP-1]
+ChameliumPortID=1
+
+[Chamelium:HDMI-A-2]
+ChameliumPortID=3
+
+[Chamelium:VGA-1]
+ChameliumPortID=4
+
+[DUT]
+SuspendResumeDelay=2
+
+Debugging the Chamelium
+-----------------------
+
+Logs that may be useful for debugging can be obtained either by connecting to
+the board via SSH or serial console and looking at the daemon logs from
+/var/log, such as:
+$ tail -f /var/log/chameleon*
+
+Daemon Source, Build and Deploy
+-------------------------------
+
+Source code for the daemon running on the Chamelium is available at:
+https://chromium.googlesource.com/chromiumos/platform/chameleon/
+
+Building the daemon requires a GNU EABI ARMv7 GCC toolchain, that must be
+specified via the CC variable, such as:
+$ make CC=arm-linux-gnueabihf-gcc
+
+The result can be deployed to the chamelium with the remote-install target and
+specifying the network address for the chamelium via the CHAMELEON_HOST
+variable, such as:
+$ make remote-install CHAMELEON_HOST=192.168.72.1
+
+The process requires the Chamelium to be connected to the Internet to succeed.
+
+Contributing Changes to the Daemon
+----------------------------------
+
+Contributions to the Chamelium daemon, just like any contribution to ChromiumOS,
+are submitted and reviewed at: https://chromium-review.googlesource.com/
+
+The ChromiumOS project provides an extensive developer guide:
+https://www.chromium.org/chromium-os/developer-guide that assumes running within
+the ChromiumOS build system. Since this is likely not the case for contributing
+to the Chamelium daemon, only the part about uploading changes is relevant:
+https://www.chromium.org/chromium-os/developer-guide#TOC-Upload-your-changes-and-get-a-code-review
+
+Most of the process is about using the Gerrit web interface for submitting and
+having the change reviewed and not forgetting the Change-Id, TEST= and BUG=
+fields in the commit.
+
+Current Support in IGT
+----------------------
+
+Support for the Chamelium platform in IGT is found in the following places:
+* lib/igt_chamelium.c: library with Chamelium-related helpers
+* tests/chamelium.c: sub-tests using the Chamelium
+
+As of late August 2017, the following features are tested by IGT:
+* Pixel-by-pixel frame integrity tests for DP and HDMI
+* Error-trend-based frame integrity tests for VGA
+* CRC-based frame integrity tests for DP and HDMI
+* Hotplug event simple tests for all interfaces
+* Hotplug event stressing tests, emulating a flaky cable for DisplayPort and
+  HDMI
+* Hotplug event during suspend test for all interfaces, either separately for
+  each interface or combined
+* EDID display identifier integrity check for all interfaces
+* EDID display identifier change during suspend for all interfaces
+
+Future Developments
+-------------------
+
+With the current generation of the hardware platform, support for testing a
+number of additional display features could be included as future developments,
+including:
+* Audio capture from HDMI and DP
+* High-bandwidth Digital Content Protection (HDCP) streaming to the display
+* Remote control forwarding (CEC) sent from the display
+* YUV colorspace for HDMI, instead of RGB
+* Partial testing of DP Multi-Stream Transport (MST) using an external MST hub
+  and the two available DP connectors of the platform
+
+While HDCP is already supported by the Chamelium daemon, features such as CEC
+and YUV are not and must be implemented there before any support for them can
+be added to IGT. Audio is supported by the Chamelium daemon for HDMI only and
+a way to retrieve the captured data via the XMLRPC interface needs to be added
+to the daemon.