Pull request feedback fix: add poll support to multiplexer

Author: Jari Poyhonen

features/cellular/framework/mux/cellular_mux.cpp

@@ -1238,4 +1238,16 @@ ssize_t Mux::user_data_rx(void* buffer, size_t size)
 }
 
 
+short Mux::poll()
+{
+    _mutex.lock();
+
+    const bool writable = (_tx_context.tx_state == TX_IDLE);
+    const bool readable = (_rx_context.rx_state == RX_SUSPEND);
+
+    _mutex.unlock();
+
+    return ((readable ? POLLIN : 0) | (writable ? POLLOUT : 0));
+}
+
 } // namespace mbed

features/cellular/framework/mux/cellular_mux.h

@@ -72,6 +72,18 @@ class MuxDataService : public FileHandle
      */
     virtual ssize_t read(void *buffer, size_t size);
 
+    /** Check for poll event flags
+     *
+     *  The input parameter can be used or ignored - could always return all events, or could check just the events
+     *  listed in events.
+     *
+     *  Call is non-blocking - returns instantaneous state of events.
+     *
+     * @param events Bitmask of poll events we're interested in - POLLIN/POLLOUT etc.
+     * @return       Bitmask of poll events that have occurred.
+     */
+    virtual short poll(short events) const;
+
     /** Not supported by the implementation. */
     virtual off_t seek(off_t offset, int whence = SEEK_SET);
 
@@ -434,6 +446,12 @@ class Mux
      */
     static ssize_t user_data_rx(void* buffer, size_t size);
 
+    /** Check for poll event flags
+     *
+     * @return Bitmask of poll events that have occurred - POLLIN/POLLOUT.
+     */
+    static short poll();
+
     /** Clear TX callback pending bit.
      *
      *  @param bit Bit to clear.

features/cellular/framework/mux/cellular_mux_data_service.cpp

@@ -31,6 +31,12 @@ ssize_t MuxDataService::read(void *buffer, size_t size)
 }
 
 
+short MuxDataService::poll(short events) const
+{
+    return Mux::poll();
+}
+
+
 off_t MuxDataService::seek(off_t offset, int whence)
 {
     MBED_ASSERT(false);