查看“CEC overview”的源代码

CEC (Consumer Electronics Control) provides enhanced functions to control devices connected through HDMI.

As an example, it allows the control of a recorder through TV remote control.

The CEC protocol is defined in the HDMI specification.

== Purpose ==
The purpose of this article is to introduce the CEC framework:
* General information
* Main components/stakeholders
* How to use the CEC framework
* Use cases

CEC is an HDMI feature designed to command and control devices connected through HDMI by using only one remote control. As an example, the remote control of a television set can be used to control a set-top box and a DVD player. Up to 15 devices can be controlled. CEC also allows individual CEC-enabled devices to command and control each other without user intervention.<ref>[https://en.wikipedia.org/wiki/Consumer_Electronics_Control Wikipedia article about CEC]</ref>

==CEC overview==
 
[[File:CECOverview.png|link=]]


===Description of the main components===

''From user space to hardware''

*'''CEC tools''' (User space)
This component contains a set of useful tools to configure CEC features.
It is hosted in v4l-utils <ref>[https://git.linuxtv.org/v4l-utils.git CEC tools source code]</ref>. 

*'''CEC core''' (Kernel space)
CEC core is the standard Linux kernel CEC framework. It manages the CEC protocol.

*'''stm32-cec''' (Kernel space)
This is the ST CEC Linux driver that handles the CEC hardware block.

*'''CEC''' (Hardware)
This is ST microprocessor [[CEC internal peripheral|CEC]] hardware block.

===Description of the APIs===
The CEC kernel API is documented in the 'CEC kernel support' section of the Linux Kernel documentation<ref>[https://www.kernel.org/doc/html/latest/media/kapi/cec-core.html Linux CEC Kernel Support]</ref>.

The CEC Userland API is documented in the 'Consumer Electronics Control API of v4l-utils documentation<ref>[https://www.linuxtv.org/downloads/v4l-dvb-apis-new/uapi/cec/cec-api.html CEC Userland API]</ref>.

==Configuration==
By default, CEC is deactivated in ST deliveries. However, you can use Linux Menuconfig tool if a specific configuration is required: [[Menuconfig or how to configure kernel | Menuconfig or how to configure kernel ]] then select:

<pre>
[*] Device Drivers --->
    [*] Multimedia support --->
        [*] HDMI-CEC support
        [*] CEC platform devices --->
            [*] STMicroelectronics STM32 HDMI-CEC driver
</pre>

== How to use CEC framework==
cec-ctl and cec-compliance tools are hosted in CEC tools use space.

To register a CEC device on CEC bus, set its type and physical address:
<pre>
{{Board$}} cec-ctl --tuner -p 1.0.0.0
Driver Info:
        Driver Name                : stm32-cec
        Adapter Name               : stm32-cec
        Capabilities               : 0x000000ef
                Physical Address
                Logical Addresses
                Transmit
                Passthrough
                Monitor All
        Driver version             : 4.19.9
        Available Logical Addresses: 4
        Physical Address           : 1.0.0.0
        Logical Address Mask       : 0x0008
        CEC Version                : 2.0
        Vendor ID                  : 0x000c03 (HDMI)
        OSD Name                   : 'Tuner'
        Logical Addresses          : 1 (Allow RC Passthrough)

          Logical Address          : 3 (Tuner 1)
            Primary Device Type    : Tuner
            Logical Address Type   : Tuner
            All Device Types       : Tuner
            RC TV Profile          : None
            Device Features        :
                None
</pre>

To debug and monitor CEC messages on bus, use the following command line:  
<pre>
{{Board$}} cec-ctl -M
Driver Info:
        Driver Name                : stm32-cec
        Adapter Name               : stm32-cec
        Capabilities               : 0x000000ef
                Physical Address
                Logical Addresses
                Transmit
                Passthrough
                Monitor All
        Driver version             : 4.19.9
        Available Logical Addresses: 4
        Physical Address           : 1.0.0.0
        Logical Address Mask       : 0x0008
        CEC Version                : 2.0
        Vendor ID                  : 0x000c03 (HDMI)
        OSD Name                   : 'Tuner'
        Logical Addresses          : 1 (Allow RC Passthrough)

          Logical Address          : 3 (Tuner 1)
            Primary Device Type    : Tuner
            Logical Address Type   : Tuner
            All Device Types       : Tuner
            RC TV Profile          : None
            Device Features        :
                None



Initial Event: State Change: PA: 1.0.0.0, LA mask: 0x000
</pre>

Run CEC compliance to check CEC bus typology:
<pre>
{{Board$}} cec-compliance -A
cec-compliance SHA                 : not available

Driver Info:
        Driver Name                : stm32-cec
        Adapter Name               : stm32-cec
        Capabilities               : 0x000000ef
                Physical Address
                Logical Addresses
                Transmit
                Passthrough
                Monitor All
        Driver version             : 4.19.9
        Available Logical Addresses: 4
        Physical Address           : 1.0.0.0
        Logical Address Mask       : 0x0008
        CEC Version                : 2.0
        Vendor ID                  : 0x000c03
        Logical Addresses          : 1 (Allow RC Passthrough)

          Logical Address          : 3
            Primary Device Type    : Tuner
            Logical Address Type   : Tuner
            All Device Types       : Tuner
            RC TV Profile          : None
            Device Features        :
                None

Compliance test for device /dev/cec0:

    The test results mean the following:
        OK                  Supported correctly by the device.
        OK (Not Supported)  Not supported and not mandatory for the device.
        OK (Presumed)       Presumably supported.  Manually check to confirm.
        OK (Unexpected)     Supported correctly but is not expected to be supported for this device.
        OK (Refused)        Supported by the device, but was refused.
        FAIL                Failed and was expected to be supported by this device.

Find remote devices:
        Polling: OK

CEC API:
        CEC_ADAP_G_CAPS: OK
        CEC_DQEVENT: OK
        CEC_ADAP_G/S_PHYS_ADDR: OK
        CEC_ADAP_G/S_LOG_ADDRS: OK
        CEC_TRANSMIT: OK
        CEC_RECEIVE: OK
        CEC_TRANSMIT/RECEIVE (non-blocking): OK (Presumed)
        CEC_G/S_MODE: OK
        CEC_EVENT_LOST_MSGS: OK

Network topology:
        System Information for device 0 (TV) from device 3 (Tuner 1):
                CEC Version                : 1.4
                Physical Address           : 0.0.0.0
                Primary Device Type        : TV
                Vendor ID                  : 0x00903e
                OSD Name                   : 'TV'
                Menu Language              : fre
                Power Status               : On

Total: 10, Succeeded: 10, Failed: 0, Warnings: 0
</pre>

Send a string to OSD:
<pre>
{{Board$}} cec-ctl --set-osd-string=disp-ctl=0x00,osd="hello" --to tv
Driver Info:
        Driver Name                : stm32-cec
        Adapter Name               : stm32-cec
        Capabilities               : 0x000000ef
                Physical Address
                Logical Addresses
                Transmit
                Passthrough
                Monitor All
        Driver version             : 4.19.9
        Available Logical Addresses: 4
        Physical Address           : 1.0.0.0
        Logical Address Mask       : 0x0008
        CEC Version                : 2.0
        Vendor ID                  : 0x000c03 (HDMI)
        OSD Name                   : 'Tuner'
        Logical Addresses          : 1 (Allow RC Passthrough)

          Logical Address          : 3 (Tuner 1)
            Primary Device Type    : Tuner
            Logical Address Type   : Tuner
            All Device Types       : Tuner
            RC TV Profile          : None
            Device Features        :
                None


Transmit from Tuner 1 to TV (3 to 0):
CEC_MSG_SET_OSD_STRING (0x64):
        disp-ctl: default (0x00)
        osd: hello
        Sequence: 347 Tx Timestamp: 2626.350s
</pre>

Get topology:
<pre>
{{Board$}} cec-ctl -S
Driver Info:
        Driver Name                : stm32-cec
        Adapter Name               : stm32-cec
        Capabilities               : 0x000000ef
                Physical Address
                Logical Addresses
                Transmit
                Passthrough
                Monitor All
        Driver version             : 4.19.9
        Available Logical Addresses: 4
        Physical Address           : 1.0.0.0
        Logical Address Mask       : 0x0008
        CEC Version                : 2.0
        Vendor ID                  : 0x000c03 (HDMI)
        OSD Name                   : 'Tuner'
        Logical Addresses          : 1 (Allow RC Passthrough)

          Logical Address          : 3 (Tuner 1)
            Primary Device Type    : Tuner
            Logical Address Type   : Tuner
            All Device Types       : Tuner
            RC TV Profile          : None
            Device Features        :
                None

        System Information for device 0 (TV) from device 3 (Tuner 1):
                CEC Version                : 1.4
                Physical Address           : 0.0.0.0
                Primary Device Type        : TV
                Vendor ID                  : 0x00903e (Philips)
                OSD Name                   : TV
                Menu Language              : fre
                Power Status               : On

        Topology:

        0.0.0.0: TV
            1.0.0.0: Tuner 1
</pre>

Send a standby message to a tv:
<pre>
{{Board$}} cec-ctl --standby --to tv
Driver Info:
        Driver Name                : stm32-cec
        Adapter Name               : stm32-cec
        Capabilities               : 0x000000ef
                Physical Address
                Logical Addresses
                Transmit
                Passthrough
                Monitor All
        Driver version             : 4.19.9
        Available Logical Addresses: 4
        Physical Address           : 1.0.0.0
        Logical Address Mask       : 0x0008
        CEC Version                : 2.0
        Vendor ID                  : 0x000c03 (HDMI)
        OSD Name                   : 'Tuner'
        Logical Addresses          : 1 (Allow RC Passthrough)

          Logical Address          : 3 (Tuner 1)
            Primary Device Type    : Tuner
            Logical Address Type   : Tuner
            All Device Types       : Tuner
            RC TV Profile          : None
            Device Features        :
                None


Transmit from Tuner 1 to TV (3 to 0):
CEC_MSG_STANDBY (0x36)
        Sequence: 371 Tx Timestamp: 2747.236s
</pre>

== Use cases==
Appplications must be added/developped in userland to support all the use cases related to CEC (eg recorder controled by TV remote control)
.<br>

{{ReviewsComments|This new paragraph section added in Framework overview template, to be completed
{{=}}{{=}}How to trace and debug the framework{{=}}{{=}}
{{=}}{{=}}{{=}}How to monitor{{=}}{{=}}{{=}}
Please give instruction to help developer/user to get information about this framework in the Linux file system:

{{=}}{{=}}{{=}}{{=}}How to monitor with debugfs{{=}}{{=}}{{=}}{{=}}

{{=}}{{=}}{{=}}{{=}}Other ways to monitor{{=}}{{=}}{{=}}{{=}}
... '''Up to framework owner to add any relevant other ways to monitor the framework, e.g. Device entry'''

{{=}}{{=}}{{=}}How to trace{{=}}{{=}}{{=}}
Please give instruction to help developer/user for getting trace(s)via : 
* dynamic debug if exist,
* specific log files if exist,
* dmesg output information,
*... '''Up to framework owner to add any relevant other ways to trace the framework'''

{{=}}{{=}}{{=}}How to debug{{=}}{{=}}{{=}}
Please give instruction to help developer/user for debugging this framework :
* with specific debug configuration,
* in case of specific use cases debug,
* ... '''Up to framework owner to add any relevant other ways to debug the framework'''
}}

==Generic source code location==
*{{CodeSource | Linux kernel | drivers/media/cec | CEC core}}
*{{CodeSource | Linux kernel | include/uapi/linux/cec.h | CEC API}}
*{{CodeSource | Linux kernel | drivers/media/platform/stm32/stm32-cec.c | stm32 CEC driver}}

==References==

<references />

<noinclude>
{{ArticleBasedOnModel | Framework overview article model}}
{{PublicationRequestId | 4962 | 2017-10-18 | AnneJ}}
[[Category:CEC]]
{{ReviewsComments|JCT 1840: alignment needed with the last version of the model<br>
[[Category:ToBeAlignedWithModel]]
}}
</noinclude>