From 0f50df41f1b5bce2cb8155c2bd19e8d8a2dda727 Mon Sep 17 00:00:00 2001
From: Nick Kraus <nick@nckraus.com>
Date: Sun, 15 Oct 2023 15:14:24 -0400
Subject: [PATCH] drivers: uart_emul: Add Emulated Errors

Allows test code to set UART errors, for driver code wanting
to test proper error handling.

Signed-off-by: Nick Kraus <nick@nckraus.com>
---
 drivers/serial/uart_emul.c                | 18 +++++++++++++++++-
 include/zephyr/drivers/serial/uart_emul.h |  8 ++++++++
 tests/drivers/uart/uart_emul/src/main.c   | 23 +++++++++++++++++++++++
 3 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/serial/uart_emul.c b/drivers/serial/uart_emul.c
index 7b3c7ca1c39..f1d90d9efb1 100644
--- a/drivers/serial/uart_emul.c
+++ b/drivers/serial/uart_emul.c
@@ -29,6 +29,7 @@ struct uart_emul_work {
 /* Device run time data */
 struct uart_emul_data {
 	struct uart_config cfg;
+	int errors;
 
 	struct ring_buf *rx_rb;
 	struct k_spinlock rx_lock;
@@ -93,7 +94,11 @@ static void uart_emul_poll_out(const struct device *dev, unsigned char out_char)
 
 static int uart_emul_err_check(const struct device *dev)
 {
-	return 0;
+	struct uart_emul_data *drv_data = dev->data;
+	int errors = drv_data->errors;
+
+	drv_data->errors = 0;
+	return errors;
 }
 
 #ifdef CONFIG_UART_USE_RUNTIME_CONFIGURE
@@ -350,6 +355,10 @@ uint32_t uart_emul_put_rx_data(const struct device *dev, uint8_t *data, size_t s
 		IF_ENABLED(CONFIG_UART_INTERRUPT_DRIVEN, (irq_en = drv_data->rx_irq_en;));
 	}
 
+	if (count < size) {
+		uart_emul_set_errors(dev, UART_ERROR_OVERRUN);
+	}
+
 	IF_ENABLED(CONFIG_UART_INTERRUPT_DRIVEN, (
 		if (count > 0 && irq_en && !empty) {
 			(void)k_work_submit(&drv_data->irq_work.work);
@@ -397,6 +406,13 @@ uint32_t uart_emul_flush_tx_data(const struct device *dev)
 	return count;
 }
 
+void uart_emul_set_errors(const struct device *dev, int errors)
+{
+	struct uart_emul_data *drv_data = dev->data;
+
+	drv_data->errors |= errors;
+}
+
 #define UART_EMUL_RX_FIFO_SIZE(inst) (DT_INST_PROP(inst, rx_fifo_size))
 #define UART_EMUL_TX_FIFO_SIZE(inst) (DT_INST_PROP(inst, tx_fifo_size))
 
diff --git a/include/zephyr/drivers/serial/uart_emul.h b/include/zephyr/drivers/serial/uart_emul.h
index 68a289841df..08e6be05b1a 100644
--- a/include/zephyr/drivers/serial/uart_emul.h
+++ b/include/zephyr/drivers/serial/uart_emul.h
@@ -83,6 +83,14 @@ uint32_t uart_emul_flush_rx_data(const struct device *dev);
  */
 uint32_t uart_emul_flush_tx_data(const struct device *dev);
 
+/**
+ * @brief Sets one or more driver errors
+ *
+ * @param dev The emulated UART device instance
+ * @param errors The @ref uart_rx_stop_reason errors to set
+ */
+void uart_emul_set_errors(const struct device *dev, int errors);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/tests/drivers/uart/uart_emul/src/main.c b/tests/drivers/uart/uart_emul/src/main.c
index af04058171f..2de2cdfbd08 100644
--- a/tests/drivers/uart/uart_emul/src/main.c
+++ b/tests/drivers/uart/uart_emul/src/main.c
@@ -40,6 +40,8 @@ static void uart_emul_before(void *f)
 
 	uart_emul_flush_rx_data(fixture->dev);
 	uart_emul_flush_tx_data(fixture->dev);
+
+	uart_err_check(fixture->dev);
 }
 
 ZTEST_F(uart_emul, test_polling_out)
@@ -78,6 +80,27 @@ ZTEST_F(uart_emul, test_polling_in)
 	zassert_equal(rc, -1, "RX buffer should be empty");
 }
 
+ZTEST_F(uart_emul, test_errors)
+{
+	int errors;
+
+	uart_emul_set_errors(fixture->dev, (UART_ERROR_PARITY | UART_ERROR_FRAMING));
+	errors = uart_err_check(fixture->dev);
+	zassert_equal(errors, (UART_ERROR_PARITY | UART_ERROR_FRAMING), "UART errors do not match");
+
+	/* uart_err_check should also clear existing errors */
+	errors = uart_err_check(fixture->dev);
+	zassert_equal(errors, 0, "Should be no errors");
+
+	/* overflowing rx buffer should produce an overrun error */
+	uart_emul_put_rx_data(fixture->dev, fixture->sample_data, SAMPLE_DATA_SIZE);
+	errors = uart_err_check(fixture->dev);
+	zassert_equal(errors, 0, "Should be no errors");
+	uart_emul_put_rx_data(fixture->dev, fixture->sample_data, SAMPLE_DATA_SIZE);
+	errors = uart_err_check(fixture->dev);
+	zassert_equal(errors, UART_ERROR_OVERRUN, "UART errors do not match");
+}
+
 static void uart_emul_isr(const struct device *dev, void *user_data)
 {
 	/* always of size SAMPLE_DATA_SIZE */