There is currently no proper wake up mechanism provided
by mbed-os. _poll_change() was supposed to wake upa blocking
poll() in case of a POLL event but the implementation was dependent
upon underlying wake up mechanism. In the absence of conditioanl
variables or some other alternative, _poll_change() wasn't able to
serve its purpose. Removing it for now. Should be implemented at some later stage
Make FileHandle more of an interface class, by requiring implementers to
provide the sigio() functionality themselves.
sigio() and poll() remain parallel independent mechanisms, so FileHandle
implementations must trigger both on state changes.
POSIX poll() provides a mechanism to attach a POLL_HUP event
if the modem or device hangs up on you. POLL_HUP and POLL_OUT are
mutually exclusive. We poll in the PPP_input() routine if the modem
hung up. If it did we stop the data consumption, close PPP and go back
to the driver for reserruction of AT parser and subsequent retries or
application specific actions.
This is achieved by attaching an interrupt to the DCD line of the modem.
When DCD line goes high (off), we have lost the carrier. So we record an
POLLHUP event using _poll_change().
BufferedSerial is a FileHandle and using SerialBase.
It keeps the SerialBase private however lets the user extend FileHandle
by keeping it public.
It is using CircularBuffer class for having circular buffers.
There are some minor amendments in CircularBuffer too.
Adding an entry for tx/rx buffer sizes in platform/mbed_lib.json.
Default size is 256 bytes.
For RTOS read(), write() calls yield for other threads to carry on with their stuff.
For non-RTOS blovking read or write would mean a loop where 100 percent resources are
consumed by this loop. Need to get a better implementation in. Currently no mechanism to
wake the mcu up after WFE.
Hasnain Virk