struct Ucs_Lld_TxMsg_* custom_next_msg_ptr

Shall be used by the LLD implementation to queue messages for asynchronous transmission.

UNICENS will set this value to NULL since only single messages are forwarded to the LLD. Within the transmit function it is recommended that the LLD queues the message for asynchronous transmission. Despite a driver's transmit function might signal busy for a short term the UNICENS library might forward multiple messages for transmission. If a driver works asynchronously (interrupt driven) it can easily use this pointer build a queue of waiting messages. Nonetheless, it is important that tx_release_fptr is invoked for every message separately. The Interface between the UNICENS library and the LLD does only support single messages.