RFC: Unstable API Change: uart_async: Call UART_RX_RDY event after rx_disable()

[nordic-krch]

Introduction

Proposal applies only to asynchronous API which currently has 3 implementations (uart_sam0, uart_nrfx_uart and uart_nrfx_uarte) and is marked as unstable.

Problem description

Currently, when rx_disable() is called then receiver is stopped and all buffers used by the instance are released (UART_RX_BUF_RELEASED event) and user is notified that receiver is disabled with UART_RX_DISABLED event. Data received between last UART_RX_RDY event and calling rx_disable() is lost. It is based on the assumption that rx_disable() is called when user is no longer interested in receiving data. However, this may not always be the case. It may be that receiver is disabled due to out of band information from the transmitter about the end of a packet. In that case, receiver is closed to reduce power consumption and it is expected that valid data will be received.

Proposed change

UART_RX_RDY event should be triggered after rx_disable() if there is new data received. If user is not interested in that data it can be discarded.

Dependencies

3 implementations would need to be updated and the test suite.

[nordic-krch]

@Sizurka @anangl @Mierunski @tbursztyka please let me know what do you think.

[nordic-krch]

Realized that API is currently labeled as "unstable". Stable API Change label removed.

[pabigot]

Seems this has been done.