modem: backend: tty: Implement transmit idle event

Implement transmit idle notification for TTY backend. Since TTY
has an "infinite" transmit buffer, we invoke transmit idle
immediately after writing the data to the TTY file.

The test suite for the TTY backend has been updated to match the
new behavior.

Signed-off-by: Bjarki Arge Andreasen <[email protected]>

Author: bjarki-andreasen

subsys/modem/backends/modem_backend_tty.c

@@ -73,8 +73,11 @@ static int modem_backend_tty_open(void *data)
 static int modem_backend_tty_transmit(void *data, const uint8_t *buf, size_t size)
 {
 	struct modem_backend_tty *backend = (struct modem_backend_tty *)data;
+	int ret;
 
-	return write(backend->tty_fd, buf, size);
+	ret = write(backend->tty_fd, buf, size);
+	modem_pipe_notify_transmit_idle(&backend->pipe);
+	return ret;
 }
 
 static int modem_backend_tty_receive(void *data, uint8_t *buf, size_t size)

tests/subsys/modem/backends/tty/src/main.c

@@ -22,7 +22,8 @@
 
 #define TEST_MODEM_BACKEND_TTY_PIPE_EVENT_OPENED_BIT (0)
 #define TEST_MODEM_BACKEND_TTY_PIPE_EVENT_RRDY_BIT   (1)
-#define TEST_MODEM_BACKEND_TTY_PIPE_EVENT_CLOSED_BIT (2)
+#define TEST_MODEM_BACKEND_TTY_PIPE_EVENT_TIDLE_BIT  (2)
+#define TEST_MODEM_BACKEND_TTY_PIPE_EVENT_CLOSED_BIT (3)
 
 #define TEST_MODEM_BACKEND_TTY_OP_DELAY (K_MSEC(1000))
 
@@ -72,6 +73,10 @@ static void modem_pipe_callback_handler(struct modem_pipe *pipe, enum modem_pipe
 		atomic_set_bit(&tty_pipe_events, TEST_MODEM_BACKEND_TTY_PIPE_EVENT_RRDY_BIT);
 		break;
 
+	case MODEM_PIPE_EVENT_TRANSMIT_IDLE:
+		atomic_set_bit(&tty_pipe_events, TEST_MODEM_BACKEND_TTY_PIPE_EVENT_TIDLE_BIT);
+		break;
+
 	case MODEM_PIPE_EVENT_CLOSED:
 		atomic_set_bit(&tty_pipe_events, TEST_MODEM_BACKEND_TTY_PIPE_EVENT_CLOSED_BIT);
 		break;
@@ -122,9 +127,13 @@ static void test_modem_backend_tty_teardown(void *f)
 /*************************************************************************************************/
 ZTEST(modem_backend_tty_suite, test_close_open)
 {
+	bool result;
+
 	zassert_ok(modem_pipe_close(tty_pipe), "Failed to close pipe");
 	zassert_ok(modem_pipe_close(tty_pipe), "Pipe should already be closed");
 	zassert_ok(modem_pipe_open(tty_pipe), "Failed to open pipe");
+	result = atomic_test_bit(&tty_pipe_events, TEST_MODEM_BACKEND_TTY_PIPE_EVENT_TIDLE_BIT);
+	zassert_true(result, "Transmit idle event should be set");
 	zassert_ok(modem_pipe_open(tty_pipe), "Pipe should already be open");
 }
 
@@ -172,12 +181,19 @@ ZTEST(modem_backend_tty_suite, test_transmit)
 {
 	int ret;
 	char msg[] = "Test me buddy 2";
+	bool result;
+
+	result = atomic_test_bit(&tty_pipe_events, TEST_MODEM_BACKEND_TTY_PIPE_EVENT_TIDLE_BIT);
+	zassert_false(result, "Transmit idle event should not be set");
 
 	ret = modem_pipe_transmit(tty_pipe, msg, sizeof(msg));
 	zassert_true(ret == sizeof(msg), "Failed to transmit using pipe");
 
 	k_sleep(TEST_MODEM_BACKEND_TTY_OP_DELAY);
 
+	result = atomic_test_bit(&tty_pipe_events, TEST_MODEM_BACKEND_TTY_PIPE_EVENT_TIDLE_BIT);
+	zassert_true(result, "Transmit idle event should be set");
+
 	ret = read(primary_fd, buffer1, sizeof(buffer1));
 	zassert_true(ret == sizeof(msg), "Read incorrect number of bytes");
 	ret = memcmp(msg, buffer1, sizeof(msg));