I've installed cec-utils on bookworm and am trying to communicate with an AV receiver.
When the device is in standby, an echo "on 5" | cec-client -s -d 1 would turn it on but after that nothing that I sent, worked any more.
In fact, when the receiver is on, even echo "scan" | cec-client -s d 1 starts returning a bunch of errors. Errors are focused on same
ioctl CEC_TRANSMIT failed - tx_status=00 errno=64
Some seconds after
Opening a connection to the CEC adapter...
It seems like every once in a while it manages to "get through" to something, so sometimes I get coherent messages on some of the devices in the HDMI network, but mostly it's error messages. When the receiver is in standby, everything seems to work as it should.
Raspberry sits in one of this receiver's input ports (HDMI 6) and audio works just fine.