cec code not working with libcec 4 - c++

Question

I am running stretch on raspberry pi 1. Only libcec4 and libcec4-dev are available in repo.
Simple code I found from github is based on old version of libcec.
// Build command:
// g++-4.8 -std=gnu++0x -fPIC -g -Wall -march=armv6 -mfpu=vfp -mfloat-abi=hard -isystem /opt/vc/include/ -isystem /opt/vc/include/interface/vcos/pthreads/ -isystem /opt/vc/include/interface/vmcs_host/linux/ -I/usr/local/include -L /opt/vc/lib -lcec -lbcm_host -ldl cec-simplest.cpp -o cec-simplest
//#CXXFLAGS=-I/usr/local/include
//#LINKFLAGS=-lcec -ldl
#include <libcec/cec.h>
// cecloader.h uses std::cout _without_ including iosfwd or iostream
// Furthermore is uses cout and not std::cout
#include <iostream>
using std::cout;
using std::endl;
#include <libcec/cecloader.h>
#include "bcm_host.h"
//#LINKFLAGS=-lbcm_host
#include <algorithm> // for std::min
// The main loop will just continue until a ctrl-C is received
#include <signal.h>
bool exit_now = false;
void handle_signal(int signal)
{
exit_now = true;
}
//CEC::CBCecKeyPressType
int on_keypress(void* not_used, const CEC::cec_keypress msg)
{
std::string key;
switch( msg.keycode )
{
case CEC::CEC_USER_CONTROL_CODE_SELECT: { key = "select"; break; }
case CEC::CEC_USER_CONTROL_CODE_UP: { key = "up"; break; }
case CEC::CEC_USER_CONTROL_CODE_DOWN: { key = "down"; break; }
case CEC::CEC_USER_CONTROL_CODE_LEFT: { key = "left"; break; }
case CEC::CEC_USER_CONTROL_CODE_RIGHT: { key = "right"; break; }
default: break;
};
std::cout << "on_keypress: " << static_cast<int>(msg.keycode) << " " << key << std::endl;
return 0;
}
int main(int argc, char* argv[])
{
// Install the ctrl-C signal handler
if( SIG_ERR == signal(SIGINT, handle_signal) )
{
std::cerr << "Failed to install the SIGINT signal handler\n";
return 1;
}
// Initialise the graphics pipeline for the raspberry pi. Yes, this is necessary.
bcm_host_init();
// Set up the CEC config and specify the keypress callback function
CEC::ICECCallbacks cec_callbacks;
CEC::libcec_configuration cec_config;
cec_config.Clear();
cec_callbacks.Clear();
const std::string devicename("CECExample");
devicename.copy(cec_config.strDeviceName, std::min(devicename.size(),13u) );
cec_config.clientVersion = CEC::LIBCEC_VERSION_CURRENT;
cec_config.bActivateSource = 0;
cec_config.callbacks = &cec_callbacks;
cec_config.deviceTypes.Add(CEC::CEC_DEVICE_TYPE_RECORDING_DEVICE);
cec_callbacks.CBCecKeyPress = &on_keypress;
// Get a cec adapter by initialising the cec library
CEC::ICECAdapter* cec_adapter = LibCecInitialise(&cec_config);
if( !cec_adapter )
{
std::cerr << "Failed loading libcec.so\n";
return 1;
}
// Try to automatically determine the CEC devices
CEC::cec_adapter devices[10];
int8_t devices_found = cec_adapter->FindAdapters(devices, 10, NULL);
if( devices_found <= 0)
{
std::cerr << "Could not automatically determine the cec adapter devices\n";
UnloadLibCec(cec_adapter);
return 1;
}
// Open a connection to the zeroth CEC device
if( !cec_adapter->Open(devices[0].comm) )
{
std::cerr << "Failed to open the CEC device on port " << devices[0].comm << std::endl;
UnloadLibCec(cec_adapter);
return 1;
}
// Loop until ctrl-C occurs
while( !exit_now )
{
// nothing to do. All happens in the CEC callback on another thread
sleep(1);
}
// Close down and cleanup
cec_adapter->Close();
UnloadLibCec(cec_adapter);
return 0;
}
It does not compile using libcec4 and libcec4-dev and throws these errors ::
cec-simplest.cpp: In function ‘int main(int, char**)’:
cec-simplest.cpp:76:19: error: ‘CEC::ICECCallbacks {aka struct CEC::ICECCallbacks}’ has no member named ‘CBCecKeyPress’; did you mean ‘keyPress’?
cec_callbacks.CBCecKeyPress = &on_keypress;
^~~~~~~~~~~~~
cec-simplest.cpp:88:41: error: ‘class CEC::ICECAdapter’ has no member named ‘FindAdapters’; did you mean ‘PingAdapter’?
int8_t devices_found = cec_adapter->FindAdapters(devices, 10, NULL);
When I renamed CBCecKeyPress to keyPress and FindAdapters to PingAdapter , I got these errors ::
cec-simplest.cpp: In function ‘int main(int, char**)’:
cec-simplest.cpp:76:33: error: invalid conversion from ‘int (*)(void*, CEC::cec_keypress)’ to ‘void (*)(void*, const cec_keypress*) {aka void (*)(void*, const CEC::cec_keypress*)}’ [-fpermissive]
cec_callbacks.keyPress = &on_keypress;
^~~~~~~~~~~~
cec-simplest.cpp:88:70: error: no matching function for call to ‘CEC::ICECAdapter::PingAdapter(CEC::cec_adapter [10], int, NULL)’
int8_t devices_found = cec_adapter->PingAdapter(devices, 10, NULL);
^
In file included from cec-simplest.cpp:5:0:
/usr/include/libcec/cec.h:77:18: note: candidate: virtual bool CEC::ICECAdapter::PingAdapter()
virtual bool PingAdapter(void) = 0;
^~~~~~~~~~~
/usr/include/libcec/cec.h:77:18: note: candidate expects 0 arguments, 3 provided
Some Info that I got about keyPress from /usr/include/libcec/cectypes.h ::
typedef struct cec_keypress
{
cec_user_control_code keycode; /**< the keycode */
unsigned int duration; /**< the duration of the keypress */
} cec_keypress;
typedef struct ICECCallbacks
{
void (CEC_CDECL* keyPress)(void* cbparam, const cec_keypress* key);
/*!
* #brief Transfer a CEC command from libCEC to the client.
* #param cbparam Callback parameter provided when the callbacks were set up
* #param command The command to transfer.
*/
void Clear(void)
{
keyPress = nullptr;
There is no documentation available for libcec.
What modifications do I need to do to make it work with libcec4 ?

Answer 1

I'm the author of the code you are asking about. I know that a year has passed since you asked the question but I only stumbled onto this stackoverflow question because I was searching for the solution myself! LOL. Luckily I've cracked the problem by myself.
I've updated the github code to work https://github.com/DrGeoff/cec_simplest and I've written a blog post about the code https://drgeoffathome.wordpress.com/2018/10/07/a-simple-libcec4-example-for-the-raspberry-pi/
In short, these are the changes I had to make. First up, the on_keypress function now is passed a pointer to a cec_keypress message rather than a by-value copy of a message. The next change is that the CEC framework has changed the name of the callback function from CBCecKeyPress to the simple keyPress. In a similar vein, the FindAdapters function is now DetectAdapters (not PingAdapters as you tried). And finally, the DetectAdapters function fills in an array of cec_adapter_descriptor rather than cec_adapter, which has the flow on effect to the Open call taking a strComName rather than simply comm.