drivers/spi: QEMU virtual SPI loopback bus for utest (#11972)

bsp/qemu-vexpress-a9/.config

@@ -436,7 +436,7 @@ CONFIG_RT_USING_POSIX_MESSAGE_SEMAPHORE=y
 #
 # CONFIG_RT_USING_RYM is not set
 # CONFIG_RT_USING_ULOG is not set
-# CONFIG_RT_USING_UTEST is not set
+CONFIG_RT_USING_UTEST=y
 # CONFIG_RT_USING_VAR_EXPORT is not set
 CONFIG_RT_USING_RESOURCE_ID=y
 CONFIG_RT_USING_ADT=y
@@ -478,7 +478,15 @@ CONFIG_RT_PAGE_MAX_ORDER=11
 #
 # RT-Thread Utestcases
 #
-# CONFIG_RT_USING_UTESTCASES is not set
+CONFIG_RT_USING_UTESTCASES=y
+    CONFIG_RT_UTEST_SPI_LOOPBACK=y
+    CONFIG_RT_UTEST_SPI_LOOPBACK_BUS_NAME="spi2"
+    CONFIG_RT_UTEST_SPI_LOOPBACK_DEV_NAME="spi_loop"
+    CONFIG_RT_UTEST_SPI_LOOPBACK_DATA_SIZE=512
+    CONFIG_RT_UTEST_SPI_LOOPBACK_MAX_HZ=10000000
+    # CONFIG_RT_UTEST_SPI_LOOPBACK_API_SMOKE is not set
+    CONFIG_RT_UTEST_SPI_LOOPBACK_TIMEOUT=60
+    # CONFIG_RT_UTEST_SPI_FLASH is not set
 # end of RT-Thread Utestcases
 
 #

bsp/qemu-vexpress-a9/rtconfig.h

@@ -225,6 +225,21 @@
 #define RT_USING_PIN
 /* end of Device Drivers */
 
+/* Utilities */
+
+#define RT_USING_UTESTCASES
+#define RT_USING_UTEST
+#define UTEST_THR_STACK_SIZE 8192
+#define UTEST_THR_PRIORITY 20
+#define RT_UTEST_MAX_OPTIONS 64
+#define RT_UTEST_SPI_LOOPBACK
+#define RT_UTEST_SPI_LOOPBACK_BUS_NAME "spi2"
+#define RT_UTEST_SPI_LOOPBACK_DEV_NAME "spi_loop"
+#define RT_UTEST_SPI_LOOPBACK_DATA_SIZE 512
+#define RT_UTEST_SPI_LOOPBACK_MAX_HZ 10000000
+#define RT_UTEST_SPI_LOOPBACK_TIMEOUT 60
+/* end of Utilities */
+
 /* C/C++ and POSIX layer */
 
 /* ISO-ANSI C layer */

components/drivers/spi/utest/Kconfig

@@ -15,6 +15,9 @@ if RT_UTEST_SPI_LOOPBACK
 config RT_UTEST_SPI_LOOPBACK_BUS_NAME
     string "SPI bus name for loopback test"
     default "spi2"
+    help
+        On BSPs without a real SPI controller (e.g. qemu-vexpress-a9) the
+        virtual loopback bus "spi2" is registered by spi_virt_bus.c.
 
 config RT_UTEST_SPI_LOOPBACK_DEV_NAME
     string "Temporary SPI device name for loopback test"

components/drivers/spi/utest/SConscript

@@ -3,10 +3,11 @@ from building import *
 
 cwd     = GetCurrentDir()
 src     = []
-CPPPATH = [cwd, cwd + '/..', cwd + '/../sfud/inc']
+CPPPATH = [cwd, cwd + '/..', cwd + '/../../include', cwd + '/../sfud/inc',
+           cwd + '/../../../utilities/utest']
 
 if GetDepend(['RT_UTEST_SPI_LOOPBACK']):
-    src += ['spi_loopback_tc.c']
+    src += ['spi_loopback_tc.c', 'spi_virt_bus.c']
 
 if GetDepend(['RT_UTEST_SPI_FLASH']):
     src += ['spi_flash_tc.c']

components/drivers/spi/utest/spi_virt_bus.c

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2006-2026, RT-Thread Development Team
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2026-11-02                      add SPI virtual loopback bus for utest
+ *
+ * A pure-software SPI bus that feeds MOSI data back to MISO. It lets the
+ * SPI loopback utest run on BSPs (such as qemu-vexpress-a9) which have no
+ * real SPI controller wired to external pins.
+ */
+
+#include <rthw.h>
+#include <rtthread.h>
+#include <rtdevice.h>
+#include <drivers/dev_spi.h>
+
+#ifdef RT_UTEST_SPI_LOOPBACK
+
+#ifndef RT_UTEST_SPI_LOOPBACK_BUS_NAME
+#define RT_UTEST_SPI_LOOPBACK_BUS_NAME "spi2"
+#endif
+
+#define SPI_VIRT_BUS_NAME       RT_UTEST_SPI_LOOPBACK_BUS_NAME
+#define SPI_VIRT_BUS_MAX_HZ     10000000
+#define SPI_VIRT_BUS_DEFAULT_HZ 1000000
+
+static struct rt_spi_bus spi_virt_bus;
+
+static rt_err_t spi_virt_configure(struct rt_spi_device *device, struct rt_spi_configuration *configuration)
+{
+    if (configuration->max_hz == 0)
+    {
+        configuration->max_hz = SPI_VIRT_BUS_DEFAULT_HZ;
+    }
+
+    if (configuration->max_hz > SPI_VIRT_BUS_MAX_HZ)
+    {
+        configuration->max_hz = SPI_VIRT_BUS_MAX_HZ;
+    }
+
+    device->config = *configuration;
+    device->config.usage_freq = configuration->max_hz;
+
+    return RT_EOK;
+}
+
+static rt_ssize_t spi_virt_xfer(struct rt_spi_device *device, struct rt_spi_message *message)
+{
+    rt_size_t i;
+
+    if (message == RT_NULL)
+    {
+        return 0;
+    }
+
+    if (message->send_buf != RT_NULL && message->recv_buf != RT_NULL)
+    {
+        rt_memcpy(message->recv_buf, message->send_buf, message->length);
+    }
+    else if (message->send_buf != RT_NULL)
+    {
+        /* TX-only: drop the data, nothing to verify. */
+    }
+    else if (message->recv_buf != RT_NULL)
+    {
+        /* RX-only: fill with a deterministic pattern. */
+        rt_uint8_t *rx = (rt_uint8_t *)message->recv_buf;
+
+        for (i = 0; i < message->length; i++)
+        {
+            rx[i] = (rt_uint8_t)(0xA5 + i);
+        }
+    }
+
+    return (rt_ssize_t)message->length;
+}
+
+static const struct rt_spi_ops spi_virt_ops = {
+    .configure = spi_virt_configure,
+    .xfer = spi_virt_xfer,
+};
+
+static int spi_virt_bus_init(void)
+{
+    return rt_spi_bus_register(&spi_virt_bus, SPI_VIRT_BUS_NAME, &spi_virt_ops);
+}
+INIT_BOARD_EXPORT(spi_virt_bus_init);
+
+#endif /* RT_UTEST_SPI_LOOPBACK */