Merge branch 'fix/usb-cdc-non-blocking-read_v5.2' into 'release/v5.2'

fix(esp_vfs_console): USB CDC read when non blocking (backport v5.2)

See merge request espressif/esp-idf!36748

components/esp_system/include/esp_private/usb_console.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2019-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2019-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -92,6 +92,14 @@ bool esp_usb_console_write_available(void);
  */
 esp_err_t esp_usb_console_set_cb(esp_usb_console_cb_t rx_cb, esp_usb_console_cb_t tx_cb, void* arg);
 
+/**
+ * @brief Call the USB interrupt handler while any interrupts
+ * are pending, but not more than a few times. Non-static to
+ * allow placement into IRAM by ldgen.
+ *
+ */
+void esp_usb_console_poll_interrupts(void); // [refactor-todo] Remove when implementing IDF-12175
+
 #ifdef __cplusplus
 }
 #endif

components/esp_vfs_console/test_apps/usb_cdc_vfs/main/test_app_main.c

@@ -0,0 +1,92 @@
+/*
+ * SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/errno.h>
+#include "unity.h"
+#include "esp_private/usb_console.h"
+#include "esp_vfs_cdcacm.h"
+
+static void flush_write(void)
+{
+    fflush(stdout);
+    fsync(fileno(stdout));
+}
+
+static void test_setup(const char* func_name, const size_t func_name_size)
+{
+    /* write the name of the test back to the pytest environment to start the test */
+    write(fileno(stdout), func_name, func_name_size);
+    write(fileno(stdout), "\n", 1);
+    flush_write();
+}
+
+static bool wait_for_read_ready(FILE *stream)
+{
+    int fd = fileno(stream);
+    fd_set read_fds;
+    FD_ZERO(&read_fds);
+    FD_SET(fd, &read_fds);
+    /* call select to wait for either a read ready or an except to happen */
+    int nread = select(fd + 1, &read_fds, NULL, NULL, NULL);
+    if ((nread >= 0) && (FD_ISSET(fd, &read_fds))) {
+        return true;
+    } else {
+        return false;
+    }
+}
+
+static void test_usb_cdc_read_non_blocking(void)
+{
+    test_setup(__func__, sizeof(__func__));
+
+    const size_t max_read_bytes = 16;
+    char read_data_buffer[max_read_bytes];
+
+    memset(read_data_buffer, 0x00, max_read_bytes);
+
+    /* reset errno to 0 for the purpose of the test to make sure it is no
+     * longer set to EWOULDBLOCK later in the test. */
+    errno = 0;
+
+    /* make sure to read in non blocking mode */
+    int stdin_fd = fileno(stdin);
+    int flags = fcntl(stdin_fd, F_GETFL);
+    flags |= O_NONBLOCK;
+    int res = fcntl(stdin_fd, F_SETFL, flags);
+    TEST_ASSERT(res == 0);
+
+    /* call read when no data is available for reading.
+     * expected result:
+     * - read returns -1 and errno has been set to EWOULDBLOCK */
+    int nread = read(stdin_fd, read_data_buffer, max_read_bytes);
+    TEST_ASSERT(nread == -1);
+    TEST_ASSERT(errno == EWOULDBLOCK);
+
+    /* reset errno to 0 for the purpose of the test to make sure it is no
+     * longer set to EWOULDBLOCK later in the test. */
+    errno = 0;
+
+    /* call read X number of bytes when less than X number of
+     * bytes are available for reading (Y bytes).
+     * expected result:
+     * - read returns at least 1 bytes errno is not set to EWOULDBLOCK */
+    char message_8[] = "send_bytes\n";
+    write(fileno(stdout), message_8, sizeof(message_8));
+    flush_write();
+
+    const bool is_ready = wait_for_read_ready(stdin);
+    TEST_ASSERT(is_ready);
+    nread = read(stdin_fd, read_data_buffer, max_read_bytes);
+    TEST_ASSERT(nread >= 1);
+    TEST_ASSERT(errno != EWOULDBLOCK);
+}
+
+void app_main(void)
+{
+    test_usb_cdc_read_non_blocking();
+}

components/esp_vfs_console/test_apps/usb_cdc_vfs/pytest_usb_cdc_vfs.py

@@ -0,0 +1,20 @@
+# SPDX-FileCopyrightText: 2024-2025 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: CC0-1.0
+import pytest
+from pytest_embedded import Dut
+
+
+@pytest.mark.esp32s3
+@pytest.mark.usb_device
+@pytest.mark.parametrize(
+    'port, flash_port, config',
+    [
+        pytest.param('/dev/serial_ports/ttyACM-esp32', '/dev/serial_ports/ttyUSB-esp32', 'release'),
+    ],
+    indirect=True,)
+@pytest.mark.parametrize('test_message', ['test123456789!@#%^&*'])
+def test_usb_cdc_vfs_default(dut: Dut, test_message: str) -> None:
+    # test run: test_usb_cdc_read_non_blocking
+    dut.expect_exact('test_usb_cdc_read_non_blocking', timeout=2)
+    dut.expect_exact('send_bytes', timeout=2)
+    dut.write('abcdefgh')

components/vfs/vfs_cdcacm.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -151,16 +151,16 @@ static ssize_t cdcacm_read(int fd, void *data, size_t size)
     ssize_t received = 0;
     _lock_acquire_recursive(&s_read_lock);
 
-    while (cdcacm_data_length_in_buffer() < size) {
+    if (s_blocking) {
-        if (!s_blocking) {
+        while (cdcacm_data_length_in_buffer() < size) {
-            errno = EWOULDBLOCK;
+            xSemaphoreTake(s_rx_semaphore, portMAX_DELAY);
-            _lock_release_recursive(&s_read_lock);
-            return -1;
         }
-        xSemaphoreTake(s_rx_semaphore, portMAX_DELAY);
+    } else {
+        /* process pending interrupts before requesting available data */
+        esp_usb_console_poll_interrupts();
+        size = MIN(size, cdcacm_data_length_in_buffer());
     }
 
-
     if (s_rx_mode == ESP_LINE_ENDINGS_CR || s_rx_mode == ESP_LINE_ENDINGS_LF) {
         /* This is easy. Just receive, and if needed replace \r by \n. */
         received = esp_usb_console_read_buf(data_c, size);