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soft_uart: demonstrate a problem with manual flush()ing 

This problem can only happen if the user is flush()ing the Rx buffer
manually by calling osmo_soft_uart_flush_rx().  Let's demonstrate it
in the unit test, so that we don't forget about it (add FIXME).

Change-Id: Iad932a505d6fd98360f90510651501f8708ff5d2
This commit is contained in:
Vadim Yanitskiy 2023-12-11 22:38:17 +07:00 committed by laforge
parent d76cc3704e
commit b392099602
2 changed files with 24 additions and 0 deletions
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20
tests/soft_uart/soft_uart_test.c
View File

@ -226,6 +226,7 @@ static void test_rx(void)
static void test_rx_flush(void)
{
struct osmo_soft_uart_cfg cfg;
struct osmo_soft_uart *suart;
SUART_TEST_BEGIN;
@ -242,6 +243,25 @@ static void test_rx_flush(void)
printf("calling osmo_soft_uart_flush_rx() while Rx enabled, but no data\n");
osmo_soft_uart_flush_rx(suart);
/* FIXME: this scenario demonstrates a problem that may occur when the user
* flushes the Rx buffer manually while the soft-UART state reflects flags
* of an incomplete symbol, for which we're waiting the stop bit. */
printf("testing corner case: manual flushing during a parity error (8-E-1)\n");
cfg = suart_test_default_cfg;
cfg.parity_mode = OSMO_SUART_PARITY_EVEN;
osmo_soft_uart_configure(suart, &cfg);
test_rx_exec(suart, "1111111" /* no data */
"0 01010101 0 1" /* even parity, correct */
"0 10101010 0 1" /* even parity, correct */
"0 11111111 1" /* odd parity, incorrect, but stop bit is pending */
"F" /* manual flush happens before receiving the stop bit */
"1" /* finally, the stop bit is received */
);
/* test_rx_exec() @ 47: flush the Rx buffer
* suart_rx_cb(flags=02): aa 55 <--- this is wrong, should be flags=00
* suart_rx_cb(flags=02): ff <--- this is expected due to odd parity */
osmo_soft_uart_free(suart);
}

4
tests/soft_uart/soft_uart_test.ok
View File

@ -71,6 +71,10 @@ Executing test_rx_flush
calling osmo_soft_uart_flush_rx() while Rx disabled
enabling the receiver
calling osmo_soft_uart_flush_rx() while Rx enabled, but no data
testing corner case: manual flushing during a parity error (8-E-1)
test_rx_exec() @ 47: flush the Rx buffer
suart_rx_cb(flags=02): aa 55
suart_rx_cb(flags=02): ff
Executing test_tx_rx
======== testing 8-N-1