Document administration details about CEC devices. This was formerly
documented in a cec-status.txt I kept on my website, but this really
belongs here as an admin guide.
Updated the original cec-status.txt, and converted it to .rst.
The old cec-drivers.rst and pulse8-cec.rst were merged into the new
cec.rst. It was overkill to keep those around, it made more sense
(at least for now) to keep it all in the new cec.rst.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
---
.../admin-guide/media/cec-drivers.rst | 10 -
Documentation/admin-guide/media/cec.rst | 367 ++++++++++++++++++
Documentation/admin-guide/media/index.rst | 3 +-
.../admin-guide/media/pulse8-cec.rst | 13 -
.../media/cec/cec-pin-error-inj.rst | 2 +
5 files changed, 371 insertions(+), 24 deletions(-)
delete mode 100644 Documentation/admin-guide/media/cec-drivers.rst
create mode 100644 Documentation/admin-guide/media/cec.rst
delete mode 100644 Documentation/admin-guide/media/pulse8-cec.rst
diff --git a/Documentation/admin-guide/media/cec-drivers.rst
b/Documentation/admin-guide/media/cec-drivers.rst
deleted file mode 100644
index 8d9686c08df9..000000000000
--- a/Documentation/admin-guide/media/cec-drivers.rst
+++ /dev/null
@@ -1,10 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-
-=================================
-CEC driver-specific documentation
-=================================
-
-.. toctree::
- :maxdepth: 2
-
- pulse8-cec
diff --git a/Documentation/admin-guide/media/cec.rst
b/Documentation/admin-guide/media/cec.rst
new file mode 100644
index 000000000000..fd681f9405ea
--- /dev/null
+++ b/Documentation/admin-guide/media/cec.rst
@@ -0,0 +1,367 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========
+HDMI CEC
+========
+
+Supported hardware in mainline
+==============================
+
+HDMI Transmitters:
+
+- Exynos4
+- Exynos5
+- STIH4xx HDMI CEC
+- V4L2 adv7511 (same HW, but a different driver from the drm adv7511)
+- stm32
+- Allwinner A10 (sun4i)
+- Raspberry Pi
+- dw-hdmi (Synopsis IP)
+- amlogic (meson ao-cec and ao-cec-g12a)
+- drm adv7511/adv7533
+- omap4
+- tegra
+- rk3288, rk3399
+- tda998x
+- DisplayPort CEC-Tunneling-over-AUX on i915, nouveau and amdgpu
+- ChromeOS EC CEC
+- CEC for SECO boards (UDOO x86).
+- Chrontel CH7322
+
+
+HDMI Receivers:
+
+- adv7604/11/12
+- adv7842
+- tc358743
+
+USB Dongles (see below for additional information on how to use these
+dongles):
+
+- Pulse-Eight: the pulse8-cec driver implements the following module
option:
+ ``persistent_config``: by default this is off, but when set to 1 the
driver
+ will store the current settings to the device's internal eeprom and
restore
+ it the next time the device is connected to the USB port.
+- RainShadow Tech. Note: this driver does not support the persistent_config
+ module option of the Pulse-Eight driver. The hardware supports it, but I
+ have no plans to add this feature. But I accept patches :-)
+
+Miscellaneous:
+
+- vivid: emulates a CEC receiver and CEC transmitter.
+ Can be used to test CEC applications without actual CEC hardware.
+
+- cec-gpio. If the CEC pin is hooked up to a GPIO pin then
+ you can control the CEC line through this driver. This supports error
+ injection as well.
+
+
+Utilities
+=========
+
+Utilities are available here: https://git.linuxtv.org/v4l-utils.git
+
+``utils/cec-ctl``: control a CEC device
+
+``utils/cec-compliance``: test compliance of a remote CEC device
+
+``utils/cec-follower``: emulate a CEC follower device
+
+Note that ``cec-ctl`` has support for the CEC Hospitality Profile as is
+used in some hotel displays. See http://www.htng.org.
+
+Note that the libcec library (https://github.com/Pulse-Eight/libcec)
supports
+the linux CEC framework.
+
+If you want to get the CEC specification, then look at the References of
+the HDMI wikipedia page: https://en.wikipedia.org/wiki/HDMI. CEC is part
+of the HDMI specification. HDMI 1.3 is freely available (very similar to
+HDMI 1.4 w.r.t. CEC) and should be good enough for most things.
+
+
+DisplayPort to HDMI Adapters with working CEC
+=============================================
+
+Background: most adapters do not support the CEC Tunneling feature,
+and of those that do many did not actually connect the CEC pin.
+Unfortunately, this means that while a CEC device is created, it
+is actually all alone in the world and will never be able to see other
+CEC devices.
+
+This is a list of known working adapters that have CEC Tunneling AND
+that properly connected the CEC pin. If you find adapters that work
+but are not in this list, then drop me a note.
+
+To test: hook up your DP-to-HDMI adapter to a CEC capable device
+(typically a TV), then run::
+
+ cec-ctl --playback # Configure the PC as a CEC Playback device
+ cec-ctl -S # Show the CEC topology
+
+The ``cec-ctl -S`` command should show at least two CEC devices,
+ourselves and the CEC device you are connected to (i.e. typically the TV).
+
+General note: I have only seen this work with the Parade PS175, PS176 and
+PS186 chipsets and the MegaChips 2900. While MegaChips 28x0 claims CEC
support,
+I have never seen it work.
+
+USB-C to HDMI
+-------------
+
+Samsung Multiport Adapter EE-PW700:
https://www.samsung.com/ie/support/model/EE-PW700BBEGWW/
+
+Kramer ADC-U31C/HF: https://www.kramerav.com/product/ADC-U31C/HF
+
+Club3D CAC-2504:
https://www.club-3d.com/en/detail/2449/usb_3.1_type_c_to_hdmi_2.0_uhd_4k_60hz_active_adapter/
+
+DisplayPort to HDMI
+-------------------
+
+Club3D CAC-1080:
https://www.club-3d.com/en/detail/2442/displayport_1.4_to_hdmi_2.0b_hdr/
+
+CableCreation (SKU: CD0712):
https://www.cablecreation.com/products/active-displayport-to-hdmi-adapter-4k-hdr
+
+Mini-DisplayPort to HDMI
+------------------------
+
+Club3D CAC-1180:
https://www.club-3d.com/en/detail/2443/mini_displayport_1.4_to_hdmi_2.0b_hdr/
+
+Note that passive adapters will never work, you need an active adapter.
+
+The Club3D adapters in this list are all MegaChips 2900 based. Other
Club3D adapters
+are PS176 based and do NOT have the CEC pin hooked up, so only the
three Club3D
+adapters above are known to work.
+
+I suspect that MegaChips 2900 based designs in general are likely to work
+whereas with the PS176 it is more hit-and-miss (mostly miss). The PS186 is
+likely to have the CEC pin hooked up, it looks like they changed the
reference
+design for that chipset.
+
+
+USB CEC Dongles
+===============
+
+These dongles appear as ``/dev/ttyACMX`` devices and need the
``inputattach``
+utility to create the ``/dev/cecX`` devices. Support for the Pulse-Eight
+has been added to ``inputattach`` 1.6.0. Support for the Rainshadow
Tech has
+been added to ``inputattach`` 1.6.1.
+
+You also need udev rules to automatically start systemd services::
+
+ SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*", ATTRS{idVendor}=="2548",
ATTRS{idProduct}=="1002", ACTION=="add", TAG+="systemd",
ENV{SYSTEMD_WANTS}+="pulse8-cec-inputattach@%k.service"
+ SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*", ATTRS{idVendor}=="2548",
ATTRS{idProduct}=="1001", ACTION=="add", TAG+="systemd",
ENV{SYSTEMD_WANTS}+="pulse8-cec-inputattach@%k.service"
+ SUBSYSTEM=="tty", KERNEL=="ttyACM[0-9]*", ATTRS{idVendor}=="04d8",
ATTRS{idProduct}=="ff59", ACTION=="add", TAG+="systemd",
ENV{SYSTEMD_WANTS}+="rainshadow-cec-inputattach@%k.service"
+
+and these systemd services:
+
+For Pulse-Eight make /lib/systemd/system/pulse8-cec-inputattach@.service::
+
+ [Unit]
+ Description=inputattach for pulse8-cec device on %I
+
+ [Service]
+ Type=simple
+ ExecStart=/usr/bin/inputattach --pulse8-cec /dev/%I
+
+For the RainShadow Tech make
/lib/systemd/system/rainshadow-cec-inputattach@.service::
+
+ [Unit]
+ Description=inputattach for rainshadow-cec device on %I
+
+ [Service]
+ Type=simple
+ ExecStart=/usr/bin/inputattach --rainshadow-cec /dev/%I
+
+
+For proper suspend/resume support create:
/lib/systemd/system/restart-cec-inputattach.service::
+
+ [Unit]
+ Description=restart inputattach for cec devices
+ After=suspend.target
+
+ [Service]
+ Type=forking
+ ExecStart=/bin/bash -c 'for d in /dev/serial/by-id/usb-Pulse-Eight*;
do /usr/bin/inputattach --daemon --pulse8-cec $d; done; for d in
/dev/serial/by-id/usb-RainShadow_Tech*; do /usr/bin/inputattach --daemon
--rainshadow-cec $d; done'
+
+ [Install]
+ WantedBy=suspend.target
+
+And run ``systemctl enable restart-cec-inputattach``.
+
+To automatically set the physical address of the CEC device whenever the
+EDID changes, you can use ``cec-ctl`` with the ``-E`` option::
+
+ cec-ctl -E /sys/class/drm/card0-DP-1/edid
+
+This assumes the dongle is connected to the card0-DP-1 output
(``xrandr`` will tell
+you which output is used) and it will poll for changes to the EDID and
update
+the Physical Address whenever they occur.
+
+To automatically run this command you can use cron. Edit crontab with
+``crontab -e`` and add this line::
+
+ @reboot /usr/local/bin/cec-ctl -E /sys/class/drm/card0-DP-1/edid
+
+This only works for display drivers that expose the EDID in
``/sys/class/drm``,
+such as the i915 driver.
+
+
+CEC Without HPD
+===============
+
+Some displays when in standby mode have no HDMI Hotplug Detect signal, but
+CEC is still enabled so connected devices can send an <Image View On> CEC
+message in order to wake up such displays. Unfortunately, not all CEC
+adapters can support this. An example is the Odroid-U3 SBC that has a
+level-shifter that is powered off when the HPD signal is low, thus
+blocking the CEC pin. Even though the SoC can use CEC without a HPD,
+the level-shifter will prevent this from functioning.
+
+There is a CEC capability flag to signal this: ``CEC_CAP_NEEDS_HPD``.
+If set, then the hardware cannot wake up displays with this behavior.
+
+Note for CEC application implementers: the <Image View On> message must
+be the first message you send, don't send any other messages before.
+Certain very bad but unfortunately not uncommon CEC implementations
+get very confused if they receive anything else but this message and
+they won't wake up.
+
+When writing a driver it can be tricky to test this. There are two
+ways to do this:
+
+1) Get a Pulse-Eight USB CEC dongle, connect an HDMI cable from your
+ device to the Pulse-Eight, but do not connect the Pulse-Eight to
+ the display.
+
+ Now configure the Pulse-Eight dongle::
+
+ cec-ctl -p0.0.0.0 --tv
+
+ and start monitoring::
+
+ sudo cec-ctl -M
+
+ On the device you are testing run::
+
+ cec-ctl --playback
+
+ It should report a physical address of f.f.f.f. Now run this
+ command::
+
+ cec-ctl -t0 --image-view-on
+
+ The Pulse-Eight should see the <Image View On> message. If not,
+ then something (hardware and/or software) is preventing the CEC
+ message from going out.
+
+ To make sure you have the wiring correct just connect the
+ Pulse-Eight to a CEC-enabled display and run the same command
+ on your device: now there is a HPD, so you should see the command
+ arriving at the Pulse-Eight.
+
+2) If you have another linux device supporting CEC without HPD, then
+ you can just connect your device to that device. Yes, you can connect
+ two HDMI outputs together. You won't have a HPD (which is what we
+ want for this test), but the second device can monitor the CEC pin.
+
+ Otherwise use the same commands as in 1.
+
+If CEC messages do not come through when there is no HPD, then you
+need to figure out why. Typically it is either a hardware restriction
+or the software powers off the CEC core when the HPD goes low. The
+first cannot be corrected of course, the second will likely required
+driver changes.
+
+
+Microcontrollers & CEC
+======================
+
+We have seen some CEC implementations in displays that use a
microcontroller
+to sample the bus. This does not have to be a problem, but some
implementations
+have timing issues. This is hard to discover unless you can hook up a
low-level
+CEC debugger (see the next section).
+
+You will see cases where the CEC transmitter holds the CEC line high or
low for
+a longer time than is allowed. For directed messages this is not a
problem since
+if that happens the message will not be Acked and it will be retransmitted.
+For broadcast messages no such mechanism exists.
+
+It's not clear what to do about this. It is probably wise to transmit some
+broadcast messages twice to reduce the chance of them being lost.
Specifically
+<Standby> and <Active Source> are candidates for that.
+
+
+Making a CEC debugger
+=====================
+
+By using a Raspberry Pi 2B/3/4 and some cheap components you can make
+your own low-level CEC debugger.
+
+Here is a picture of my setup:
+
+https://hverkuil.home.xs4all.nl/rpi3-cec.jpg
+
+It's a Raspberry Pi 3 together with a breadboard and some breadboard wires:
+
+http://www.dx.com/p/diy-40p-male-to-female-male-to-male-female-to-female-dupont-line-wire-3pcs-356089#.WYLOOXWGN7I
+
+Finally on of these HDMI female-female passthrough connectors (full
soldering type 1):
+
+https://elabbay.myshopify.com/collections/camera/products/hdmi-af-af-v1a-hdmi-type-a-female-to-hdmi-type-a-female-pass-through-adapter-breakout-board?variant=45533926147
+
+We've tested this and it works up to 4kp30 (297 MHz). The quality is
not high
+enough to pass-through 4kp60 (594 MHz).
+
+I also added an RTC and a breakout shield:
+
+https://www.amazon.com/Makerfire%C2%AE-Raspberry-Module-DS1307-Battery/dp/B00ZOXWHK4
+
+https://www.dx.com/p/raspberry-pi-gpio-expansion-board-breadboard-easy-multiplexing-board-one-to-three-with-screw-for-raspberry-pi-2-3-b-b-2729992.html#.YGRCG0MzZ7I
+
+These two are not needed but they make life a bit easier.
+
+If you want to monitor the HPD line as well, then you need one of these
+level shifters:
+
+https://www.adafruit.com/product/757
+
+(This is just where I got these components, there are many other places you
+can get similar things).
+
+The CEC pin of the HDMI connector needs to be connected to these pins:
+CE0/IO8 and CE1/IO7 (pull-up GPIOs). The (optional) HPD pin of the HDMI
+connector should be connected (via a level shifter to convert the 5V
+to 3.3V) to these pins: IO17 and IO27. The (optional) 5V pin of the HDMI
+connector should be connected (via a level shifter) to these pins: IO22
+and IO24. Monitoring the HPD an 5V lines is not necessary, but it is
helpful.
+
+This kernel patch will hook up the cec-gpio driver correctly to
+e.g. ``arch/arm/boot/dts/bcm2837-rpi-3-b-plus.dts``::
+
+ cec-gpio@7 {
+ compatible = "cec-gpio";
+ cec-gpios = <&gpio 7 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>;
+ hpd-gpios = <&gpio 17 GPIO_ACTIVE_HIGH>;
+ v5-gpios = <&gpio 22 GPIO_ACTIVE_HIGH>;
+ };
+
+ cec-gpio@8 {
+ compatible = "cec-gpio";
+ cec-gpios = <&gpio 8 (GPIO_ACTIVE_HIGH|GPIO_OPEN_DRAIN)>;
+ hpd-gpios = <&gpio 27 GPIO_ACTIVE_HIGH>;
+ v5-gpios = <&gpio 24 GPIO_ACTIVE_HIGH>;
+ };
+
+This dts change will enable two cec GPIO devices: I typically use one to
+send/receive CEC commands and the other to monitor. If you monitor using
+an unconfigured CEC adapter then it will use GPIO interrupts which makes
+monitoring very accurate.
+
+The documentation on how to use the error injection is here:
:ref:`cec_pin_error_inj`.
+
+``cec-ctl --monitor-pin`` will do low-level CEC bus sniffing and analysis.
+You can also store the CEC traffic to file using ``--store-pin`` and
analyze
+it later using ``--analyze-pin``.
+
+You can also use this as a full-fledged CEC device by configuring it
+using ``cec-ctl --tv -p0.0.0.0`` or ``cec-ctl --playback -p1.0.0.0``.
diff --git a/Documentation/admin-guide/media/index.rst
b/Documentation/admin-guide/media/index.rst
index c676af665111..43f4a292b245 100644
--- a/Documentation/admin-guide/media/index.rst
+++ b/Documentation/admin-guide/media/index.rst
@@ -38,13 +38,14 @@ The media subsystem
remote-controller
+ cec
+
dvb
cardlist
v4l-drivers
dvb-drivers
- cec-drivers
**Copyright** |copy| 1999-2020 : LinuxTV Developers
diff --git a/Documentation/admin-guide/media/pulse8-cec.rst
b/Documentation/admin-guide/media/pulse8-cec.rst
deleted file mode 100644
index 356d08b519f3..000000000000
--- a/Documentation/admin-guide/media/pulse8-cec.rst
+++ /dev/null
@@ -1,13 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-
-Pulse-Eight CEC Adapter driver
-==============================
-
-The pulse8-cec driver implements the following module option:
-
-``persistent_config``
----------------------
-
-By default this is off, but when set to 1 the driver will store the current
-settings to the device's internal eeprom and restore it the next time the
-device is connected to the USB port.
diff --git a/Documentation/userspace-api/media/cec/cec-pin-error-inj.rst
b/Documentation/userspace-api/media/cec/cec-pin-error-inj.rst
index b0efce40471f..411d42a742f3 100644
--- a/Documentation/userspace-api/media/cec/cec-pin-error-inj.rst
+++ b/Documentation/userspace-api/media/cec/cec-pin-error-inj.rst
@@ -1,5 +1,7 @@
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. _cec_pin_error_inj:
+
CEC Pin Framework Error Injection
=================================
--
2.35.1
