feat(vfs): Add function to dump VFS file descriptors

components/vfs/include/esp_vfs.h

@@ -469,6 +469,25 @@ ssize_t esp_vfs_pread(int fd, void *dst, size_t size, off_t offset);
  */
 ssize_t esp_vfs_pwrite(int fd, const void *src, size_t size, off_t offset);
 
+/**
+ *
+ * @brief Dump the existing VFS FDs data to FILE* fp
+ *
+ * Dump the FDs in the format:
+ @verbatim
+         <VFS Path Prefix>-<FD seen by App>-<FD seen by driver>
+
+    where:
+     VFS Path Prefix   : file prefix used in the esp_vfs_register call
+     FD seen by App    : file descriptor returned by the vfs to the application for the path prefix
+     FD seen by driver : file descriptor used by the driver for the same file prefix.
+
+ @endverbatim
+ *
+ * @param fp         File descriptor where data will be dumped
+ */
+void esp_vfs_dump_fds(FILE *fp);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif

components/vfs/test_apps/main/test_vfs_fd.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -18,6 +18,10 @@
 #include "esp_log.h"
 #include "test_utils.h"
 #include "ccomp_timer.h"
+#include "driver/uart.h"
+#include "driver/uart_vfs.h"
+#include "lwip/sockets.h"
+#include "lwip/netdb.h"
 
 #define VFS_PREF1       "/vfs1"
 #define VFS_PREF2       "/vfs2"
@@ -289,3 +293,44 @@ TEST_CASE("esp_vfs_register_fd_range checks for overlap", "[vfs]")
     TEST_ESP_OK(esp_vfs_unregister("/test"));
     TEST_ESP_ERR(ESP_ERR_INVALID_ARG, err);
 }
+
+static void socket_init(int *socket_fd)
+{
+    const struct addrinfo hints = {
+        .ai_family = AF_INET,
+        .ai_socktype = SOCK_DGRAM,
+    };
+    struct addrinfo *res;
+    int err;
+
+    err = getaddrinfo("localhost", "80", &hints, &res);
+    TEST_ASSERT_EQUAL(err, 0);
+    TEST_ASSERT_NOT_NULL(res);
+
+    *socket_fd = socket(res->ai_family, res->ai_socktype, 0);
+    TEST_ASSERT(*socket_fd >= 0);
+    freeaddrinfo(res);
+}
+
+TEST_CASE("esp_vfs_dump_fds displays all registered fds in vfs", "[vfs]")
+{
+    int uart_fd0, uart_fd1, uart_fd2;
+    int socket_fd=-1;
+
+    uart_fd0 = open("/dev/uart/0", O_RDWR);
+    TEST_ASSERT_NOT_EQUAL_MESSAGE(uart_fd0, -1, "Cannot open UART");
+    uart_fd1 = open("/dev/uart/1", O_RDWR);
+    TEST_ASSERT_NOT_EQUAL_MESSAGE(uart_fd1, -1, "Cannot open UART");
+    uart_fd2 = open("/dev/uart/1", O_RDWR);
+    TEST_ASSERT_NOT_EQUAL_MESSAGE(uart_fd2, -1, "Cannot open UART");
+
+    test_case_uses_tcpip();
+    socket_init(&socket_fd);
+
+    esp_vfs_dump_fds(stdout);
+
+    close(uart_fd0);
+    close(uart_fd1);
+    close(uart_fd2);
+    close(socket_fd);
+}

components/vfs/vfs.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -270,6 +270,26 @@ esp_err_t esp_vfs_unregister_fd(esp_vfs_id_t vfs_id, int fd)
     return ret;
 }
 
+void esp_vfs_dump_fds(FILE *fp)
+{
+    const vfs_entry_t* vfs;
+    fprintf(fp, "------------------------------------------------------\n");
+    fprintf(fp, "<VFS Path Prefix>-<FD seen by App>-<FD seen by driver>\n");
+    fprintf(fp, "------------------------------------------------------\n");
+    _lock_acquire(&s_fd_table_lock);
+    for (int index = 0; index < MAX_FDS; index++) {
+        if (s_fd_table[index].vfs_index != -1) {
+            vfs = s_vfs[s_fd_table[index].vfs_index];
+            if (strcmp(vfs->path_prefix, "")) {
+                fprintf(fp, "(%s) - 0x%x - 0x%x\n", vfs->path_prefix, index, s_fd_table[index].local_fd);
+            } else {
+                fprintf(fp, "(socket) - 0x%x - 0x%x\n", index, s_fd_table[index].local_fd);
+            }
+        }
+    }
+    _lock_release(&s_fd_table_lock);
+}
+
 /*
  * Set ESP_VFS_FLAG_READONLY_FS read-only flag for a registered virtual filesystem
  * for given path prefix. Should be only called from the esp_vfs_*filesystem* register