test: logging: add testcase for multi-instance log backend uart

Add testcase for the multi-instance log backend uart using
emulated uart.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>

tests/subsys/logging/log_backend_uart/CMakeLists.txt

@@ -0,0 +1,9 @@
+# Copyright (c) 2023 Meta
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(log_backend_uart_test)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

tests/subsys/logging/log_backend_uart/Kconfig

@@ -0,0 +1,8 @@
+# Copyright (c) 2021 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+module = SAMPLE_MODULE
+module-str = Test logging API
+source "subsys/logging/Kconfig.template.log_config"
+
+source "Kconfig.zephyr"

tests/subsys/logging/log_backend_uart/multi.overlay

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2023 Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	chosen {
+		zephyr,log-uart = &log_uarts;
+	};
+
+	log_uarts: log_uarts {
+		compatible = "zephyr,log-uart";
+		uarts = <&euart0 &euart1>;
+	};
+
+	euart0: uart-emul0 {
+		compatible = "zephyr,uart-emul";
+		status = "okay";
+		current-speed = <0>;
+		rx-fifo-size = <256>;
+		tx-fifo-size = <256>;
+	};
+
+	euart1: uart-emul1 {
+		compatible = "zephyr,uart-emul";
+		status = "okay";
+		current-speed = <0>;
+		rx-fifo-size = <256>;
+		tx-fifo-size = <256>;
+	};
+};

tests/subsys/logging/log_backend_uart/prj.conf

@@ -0,0 +1,11 @@
+# Copyright (c) 2023 Meta
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_ZTEST=y
+CONFIG_ASSERT=y
+CONFIG_TEST_LOGGING_DEFAULTS=n
+
+CONFIG_LOG=y
+CONFIG_LOG_BACKEND_UART=y
+CONFIG_LOG_MODE_IMMEDIATE=y
+CONFIG_LOG_PRINTK=n

tests/subsys/logging/log_backend_uart/single.overlay

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2023 Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	chosen {
+		zephyr,log-uart = &log_uarts;
+	};
+
+	log_uarts: log_uarts {
+		compatible = "zephyr,log-uart";
+		uarts = <&euart0>;
+	};
+
+	euart0: uart-emul0 {
+		compatible = "zephyr,uart-emul";
+		status = "okay";
+		current-speed = <0>;
+		rx-fifo-size = <256>;
+		tx-fifo-size = <256>;
+	};
+};

tests/subsys/logging/log_backend_uart/src/main.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2023 Meta
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/ztest.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/logging/log_backend.h>
+#include <zephyr/drivers/uart.h>
+#include <zephyr/drivers/serial/uart_emul.h>
+
+LOG_MODULE_REGISTER(test, CONFIG_SAMPLE_MODULE_LOG_LEVEL);
+
+#define EMUL_UART_NUM             DT_NUM_INST_STATUS_OKAY(zephyr_uart_emul)
+#define EMUL_UART_NODE(i)         DT_NODELABEL(euart##i)
+#define EMUL_UART_DEV_INIT(i, _)  DEVICE_DT_GET(EMUL_UART_NODE(i))
+#define EMUL_UART_TX_FIFO_SIZE(i) DT_PROP(EMUL_UART_NODE(i), tx_fifo_size)
+#define SAMPLE_DATA_SIZE          EMUL_UART_TX_FIFO_SIZE(0)
+
+#define TEST_DATA "0123456789ABCDEF"
+BUILD_ASSERT(strlen(TEST_DATA) < SAMPLE_DATA_SIZE);
+
+struct log_backend_uart_fixture {
+	const struct device *dev[EMUL_UART_NUM];
+};
+
+static void *uart_emul_setup(void)
+{
+	static struct log_backend_uart_fixture fixture = {
+		.dev = {LISTIFY(EMUL_UART_NUM, EMUL_UART_DEV_INIT, (,))}};
+
+	for (size_t i = 0; i < EMUL_UART_NUM; i++) {
+		zassert_not_null(fixture.dev[i]);
+	}
+
+	return &fixture;
+}
+
+static void uart_emul_before(void *f)
+{
+	struct log_backend_uart_fixture *fixture = f;
+
+	for (size_t i = 0; i < EMUL_UART_NUM; i++) {
+		uart_irq_tx_disable(fixture->dev[i]);
+		uart_irq_rx_disable(fixture->dev[i]);
+
+		uart_emul_flush_rx_data(fixture->dev[i]);
+		uart_emul_flush_tx_data(fixture->dev[i]);
+
+		uart_err_check(fixture->dev[i]);
+	}
+}
+
+ZTEST_F(log_backend_uart, test_log_backend_uart_multi_instance)
+{
+	zassert_equal(log_backend_count_get(), EMUL_UART_NUM, "Unexpected number of instance(s)");
+
+	LOG_RAW(TEST_DATA);
+
+	for (size_t i = 0; i < EMUL_UART_NUM; i++) {
+		uint8_t tx_content[SAMPLE_DATA_SIZE] = {0};
+		size_t tx_len;
+
+		tx_len = uart_emul_get_tx_data(fixture->dev[i], tx_content, sizeof(tx_content));
+		zassert_equal(tx_len, strlen(TEST_DATA),
+			      "%d: TX buffer length does not match. Expected %d, got %d",
+			      i, strlen(TEST_DATA), tx_len);
+		zassert_mem_equal(tx_content, TEST_DATA, strlen(tx_content));
+	}
+}
+
+ZTEST_SUITE(log_backend_uart, NULL, uart_emul_setup, uart_emul_before, NULL, NULL);

tests/subsys/logging/log_backend_uart/testcase.yaml

@@ -0,0 +1,14 @@
+# Copyright (c) 2023 Meta
+# SPDX-License-Identifier: Apache-2.0
+
+common:
+  tags:
+    - logging
+    - backend
+    - uart
+  platform_allow: qemu_x86
+tests:
+  logging.backend.uart.single:
+    extra_args: DTC_OVERLAY_FILE="./single.overlay"
+  logging.backend.uart.multi:
+    extra_args: DTC_OVERLAY_FILE="./multi.overlay"