log

Application:

• DEFERRED: every call to LOG_sth puts a log entry into ringbuffer.

Frontend:

• DEFERRED: Application calls nrf_log_frontend_dequeue() and:
  • one entry is pop-ed from ringbuffer
  • new memobj is allocated from log_mempool to fit log entry.
  • all registered backends are iterated:
    • check if backend is enabled nrf_log_backend_is_enabled(p_backend)
    • filters: check if module log level and log entry severity level matches
    • if log entry should be send to backend - call nrf_log_backend_put
    • BACKEND: process log entry and do really printf-like processing and sending / TX-ing / storing

<uml> participant Application as APP queue “Circular Buffer\nNRF_LOG_BUFSIZE” as CB queue “log_mempool\ndynamic memory pool” as MEM control “nrf_log_frontend_dequeue()” as DE note over MEM NRF_LOG_MSGPOOL_ELEMENT_SIZE

• *x NRF_LOG_MSGPOOL_ELEMENT_COUNT endnote control “backend RTT” as B1 control “backend UART” as B2 control “backend x” as B3 APP → CB: NRF_LOG_INFO() activate CB APP → CB: NRF_LOG_DEBUG() activate CB APP → CB: NRF_LOG_HEXDUMP() activate CB … APP → DE: NRF_LOG_PROCESS() activate DE DE ←- MEM: nrf_memobj_alloc() activate MEM activate DE CB –> DE: pop one entry deactivate CB DE –> DE: copy entry to allocated\nmempool object DE ←- DE: backend1:\ncheck filters and status DE –> B1: mempool object DE ←- DE: backend2:\ncheck filters and status DE –> B2: mempool object DE ←- DE: backend3:\ncheck filters and status DE –> B3: mempool object MEM ←- DE: nrf_memobj_put() deactivate MEM DE –> APP: return “circular buffer is empty” deactivate DE deactivate DE </uml> ===== buffer sizes ===== * Circular buffer of NRF_LOG_BUFSIZE (1024)** - used only when deferred. Its aim is to store log entry from app as fast as poosible without further processing.
• Dynamic memory pool
• size is NRF_LOG_MSGPOOL_ELEMENT_SIZE (20) x NRF_LOG_MSGPOOL_ELEMENT_COUNT (8)
• provides dynamic memory access, even to fragmented memory (special functions to access pool must be used)
• storage for log entries qualified to be passed to backends
• provides get/put counting semaphore locking mechanism, so one log entry can be passed to multiple log backends at time.
• Backends are using temporary string buffers - this is the real place where printf-like function writes generated strings.
• NRF_LOG_BACKEND_UART_TEMP_BUFFER_SIZE 64