fix/feat(uart): uart_read_bytes() timeout fixed, added uart_read_bytes_partial() (IDFGH-16315)

[BitsForPeople]

Description

fix: uart_read_bytes() did not correctly handle the given ticks_to_wait timeout; when trying to read N bytes from the UART, it could take up to (N+1) * ticks_to_wait ticks to return. The new version returns as soon as ticks_to_wait ticks have elapsed.
This change may in theory break applications which implicitly relied on the the given time limit not being honored.

feat: New function uart_read_bytes_partial() - blocks until any data is read from the RX buffer, not until the given buffer is full. Useful when you don't know in advance exactly how many bytes you expect to receive and you still want to react quickly to received data. This method also allows tasks to 'synchronize' to the UART's RX interrupt and consequently to more directly match the UART's behavior defined via the RX_FULL_THRESH and RX_TOUT settings.

Related

Testing

Wrote a test application using UART loop-back to verify specifically the timing behavior of both uart_read_bytes() and uart_read_bytes_partial(), ran it on an -S3.

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[songruo]

uart_read_bytes() did not correctly handle the given ticks_to_wait timeout
I agree.

New function uart_read_bytes_partial() - blocks until any data is read from the RX buffer, not until the given buffer is full.
You can utilize UART_DATA event to achieve the same purpose. This is some logic you can do in the application layer, using UART_DATA + ticks counting.

[BitsForPeople]

You're right in that you can achieve the same overall behavior as uart_read_bytes_partial() by using UART events. That's a whole different programming paradigm though from simple blocking reads.
You can, and people do, also emulate this behavior in user code by using uart_read_bytes() with an initial buffer length of 1 to wait for any data, but that's a bit clumsy and inefficient.

I'd argue that uart_read_bytes_partial() actually does what people usually expect uart_read_bytes() to do, before they realize that it doesn't. At least that's what a) I'd expect it to do, and b) people somewhat regularily ask for in the forums.