UDP packets are always received as OOB data. Without checking for
new OOB data with a call to "_process_oob" then recv_udp never blocks.
If a UDP packet is not available then NSAPI_ERROR_WOULD_BLOCK is
returned. This causes mbed-os's DNS handling to always fail when
flow control is enabled.
This patch fixes recv_udp by always calling "_process_oob" regardless
of if flow control is enabled. This ensures that recv_udp follows the
timeout parameter and waits for new data to arrive.
When using UARTSerial sending data over the uart follows the sequence
below:
<-TX done ISR runs and sets a software interrupt to pending
<-Software interrupt fires:
-disables TX done interrupt
-calls UARTSerial TX handler which sends bytes until the uart
buffer filled (writeable returns false). Sending a byte
re-enables the TX done interrupt continuing the cycle
Due to this sequence, if the UARTSerial TX handler does not send a byte
then the transmit state machine mentioned above will get stuck with
the TX done interrupt disabled. The events causing this failure:
<-TX done ISR runs and sets a software interrupt to pending
<-Software interrupt fires:
-disables TX done interrupt
-calls UARTSerial TX handler:
-checks writeable which is true and sends a byte
<- interrupted by a higher priority interrrupt
<- TX done ISR runs, setting software interrupt to
pending again
-checks writeable which is true and sends a second byte
-Software interrupt finishes
<-Software interrupt fires:
-disables TX done interrupt
-calls UARTSerial TX handler:
-checks writeable which is false and DOES NOT SEND A BYTE
-Software interrupt finishes, the TX interrupt is still disabled
*-Byte gets sent but TX done ISR does not fire
This patch prevents the TX lockup by removing the code in the
software interrupt which disables the TX done interrupt. Disabling the
TX done interrupt at this point is not necessary so this code is safe
to remove.
Unlike the public address, the RANDOM address is guaranteed to exist.
If privacy is enabled, it means the controller will generates random resolvable addresses or non resolvable addresses depending on the config.
If privacy is not enabled then the device will use the device's random static address that doesn't change between radio processes.
With support for checking H/W UART initialized or not, we can simplify stdio management:
1. When serial_init(&stdio_uart) calls in, just set the 'stdio_uart_inited' flag.
2. When serial_free(&stdio_uart) calls in, just clear the 'stdio_uart_inited' flag.
Except above, we needn't make special handling with 'stdio_uart'.