UART PAL requirements in multi-threaded OS

[jkcko]

In a multi-threaded OS environment where where UART TX and RX processing may be done in a separate thread is it okay to call otPlatUartSendDone() and otPlatUartReceived() from another thread than the main OpenThread thread which calls otTaskletsProcess?

[abtink]

Generally no. All public OT APIs and platform callbacks should be called from same OS context (task/thread).

You can refer to the specific API documentation to see if it explicitly allows calls from different contexts. I know of only one example otPlatSpiSlaveTransactionCompleteCallback:

openthread/include/openthread/platform/spi-slave.h

Lines 67 to 70 in f0b6fce

	* This callback can be called from ISR context. The return value from this function indicates if any further
	* processing is required. If `TRUE` is returned the platform spi-slave driver implementation must invoke the
	* transaction process callback (`aProcessCallback` set in `otPlatSpiSlaveEnable()`) which unlike this callback must be
	* called from the same OS context that any other OpenThread API/callback is called.

)