feat(storage/vfs): add /dev/null for unwanted output redirection

components/esp_system/system_init_fn.txt

@@ -50,6 +50,7 @@ CORE: 105: init_newlib_time in components/esp_system/startup_funcs.c on BIT(0)
 CORE: 110: init_vfs_uart in components/esp_driver_uart/src/uart_vfs.c on BIT(0)
 CORE: 111: init_vfs_usj in components/esp_driver_usb_serial_jtag/src/usb_serial_jtag_vfs.c on BIT(0)
 CORE: 112: init_vfs_usj_sec in components/esp_driver_usb_serial_jtag/src/usb_serial_jtag_vfs.c on BIT(0)
+CORE: 113: init_vfs_nullfs in components/vfs/nullfs.c on BIT(0)
 CORE: 114: init_vfs_console in components/esp_vfs_console/vfs_console.c on BIT(0)
 CORE: 115: init_newlib_stdio in components/newlib/newlib_init.c on BIT(0)
 

components/esp_system/test_apps/console/main/test_app_main.c

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 #include <stdio.h>
+#include <assert.h>
 #include "sdkconfig.h"
 
 #include "esp_rom_uart.h"
@@ -15,6 +16,9 @@
 #include "driver/uart.h"
 #include "soc/uart_channel.h"
 
+#include <fcntl.h>
+#include <unistd.h>
+
 #if CONFIG_ESP_CONSOLE_NONE
 /* Set up UART on UART_0 (console) to be able to
    notify pytest test case that app booted successfully
@@ -49,6 +53,15 @@ void app_main(void)
 {
     printf("Hello World\n");
 
+    int fd = open("/dev/null", O_RDWR);
+    assert(fd >= 0); // Standard check
+
+    // Check if correct file descriptor is returned
+    // In this case it should be neither of 0, 1, 2 (== stdin, stdout, stderr)
+    assert(fd > 2);
+
+    close(fd);
+
 #if CONFIG_ESP_CONSOLE_NONE
     console_none_print();
 #endif // CONFIG_ESP_CONSOLE_NONE

components/esp_vfs_console/vfs_console.c

@@ -15,6 +15,7 @@
 #include "esp_vfs_console.h"
 #include "sdkconfig.h"
 #include "esp_private/startup_internal.h"
+#include "esp_vfs_null.h"
 
 #define STRINGIFY(s) STRINGIFY2(s)
 #define STRINGIFY2(s) #s
@@ -52,6 +53,8 @@ int console_open(const char * path, int flags, int mode)
     vfs_console.fd_primary = open("/dev/usbserjtag", flags, mode);
 #elif CONFIG_ESP_CONSOLE_USB_CDC
     vfs_console.fd_primary = open("/dev/cdcacm", flags, mode);
+#else
+    vfs_console.fd_primary = open("/dev/null", flags, mode);
 #endif
 
 // Secondary port open
@@ -207,13 +210,15 @@ esp_err_t esp_vfs_console_register(void)
     if (err != ESP_OK) {
         return err;
     }
+#else
+    esp_vfs_null_register();
+    primary_vfs = esp_vfs_null_get_vfs();
 #endif
 
 // Secondary vfs part.
 #if CONFIG_ESP_CONSOLE_SECONDARY_USB_SERIAL_JTAG
     secondary_vfs = esp_vfs_usb_serial_jtag_get_vfs();
 #endif
-
     err = esp_vfs_dev_console_register();
     return err;
 }

components/vfs/CMakeLists.txt

@@ -7,6 +7,7 @@ endif()
 list(APPEND sources "vfs.c"
                     "vfs_eventfd.c"
                     "vfs_semihost.c"
+                    "nullfs.c"
                     )
 
 list(APPEND pr esp_timer

components/vfs/include/esp_vfs_null.h

@@ -0,0 +1,31 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#pragma once
+
+#include "esp_vfs.h"
+#include "esp_err.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Get VFS structure for /dev/null
+ *
+ * @return VFS structure for /dev/null
+ */
+const esp_vfs_t *esp_vfs_null_get_vfs(void);
+
+/**
+ * @brief Register filesystem for /dev/null
+ *
+ * @return ESP_OK on success; any other value indicates an error
+ */
+esp_err_t esp_vfs_null_register(void);
+
+#ifdef __cplusplus
+}
+#endif

components/vfs/nullfs.c

@@ -0,0 +1,297 @@
+/*
+ * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <stdio.h>
+#include <sys/types.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/errno.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include "esp_vfs.h"
+#include "esp_log.h"
+#include "esp_private/startup_internal.h"
+
+#include "esp_vfs_null.h"
+
+#define UNUSED(x) (void)(x)
+typedef enum {
+    VFS_NULL_CLOSED = 0,
+    VFS_NULL_READ = 1 << 0,
+    VFS_NULL_WRITE = 1 << 1,
+} vfs_null_flags_t;
+
+typedef uint64_t vfs_null_ctx_t;
+
+#define GET_FLAGS(ctx, fd) ((ctx >> (fd * 2)) & 0x3)
+#define SET_FLAGS(ctx, fd, flags) (ctx |= (flags << (fd * 2)))
+
+#define WRITABLE(ctx, fd) (GET_FLAGS(ctx, fd) & VFS_NULL_WRITE)
+#define READABLE(ctx, fd) (GET_FLAGS(ctx, fd) & VFS_NULL_READ)
+
+#define SET_WRITABLE(ctx, fd) SET_FLAGS(ctx, fd, VFS_NULL_WRITE)
+#define SET_READABLE(ctx, fd) SET_FLAGS(ctx, fd, VFS_NULL_READ)
+
+#define FD_IN_RANGE(fd) (fd >= 0 && fd < 32)
+
+static vfs_null_ctx_t g_fds = 0;
+
+static const char* TAG = "nullfs";
+
+static ssize_t vfs_null_write(int fd, const void *data, size_t size);
+static off_t vfs_null_lseek(int fd, off_t offset, int whence);
+static ssize_t vfs_null_read(int fd, void *data, size_t size);
+static ssize_t vfs_null_pread(int fd, void *data, size_t size, off_t offset);
+static ssize_t vfs_null_pwrite(int fd, const void *data, size_t size, off_t offset);
+static int vfs_null_open(const char* path, int flags, int mode);
+static int vfs_null_close(int fd);
+static int vfs_null_fstat(int fd, struct stat *st);
+#if CONFIG_VFS_SUPPORT_DIR
+static int vfs_null_stat(const char* path, struct stat *st);
+#endif // CONFIG_VFS_SUPPORT_DIR
+static int vfs_null_fcntl(int fd, int cmd, int arg);
+static int vfs_null_ioctl(int fd, int cmd, va_list args);
+static int vfs_null_fsync(int fd);
+
+static const esp_vfs_t s_vfs_null = {
+    .flags = ESP_VFS_FLAG_DEFAULT,
+    .write = &vfs_null_write,
+    .lseek = &vfs_null_lseek,
+    .read = &vfs_null_read,
+    .pread = &vfs_null_pread,
+    .pwrite = &vfs_null_pwrite,
+    .open = &vfs_null_open,
+    .close = &vfs_null_close,
+    .fstat = &vfs_null_fstat,
+#if CONFIG_VFS_SUPPORT_DIR
+    .stat = &vfs_null_stat,
+#endif // CONFIG_VFS_SUPPORT_DIR
+    .fcntl = &vfs_null_fcntl,
+    .ioctl = &vfs_null_ioctl,
+    .fsync = &vfs_null_fsync,
+};
+
+const esp_vfs_t *esp_vfs_null_get_vfs(void)
+{
+    return &s_vfs_null;
+}
+
+esp_err_t esp_vfs_null_register(void)
+{
+    return esp_vfs_register("/dev/null", &s_vfs_null, NULL);
+}
+
+static ssize_t vfs_null_write(int fd, const void *data, size_t size)
+{
+    UNUSED(fd);
+    UNUSED(data);
+
+    if (FD_IN_RANGE(fd) && WRITABLE(g_fds, fd)) {
+        return size;
+    }
+
+    errno = EBADF;
+    return -1;
+}
+
+static off_t vfs_null_lseek(int fd, off_t offset, int whence)
+{
+    UNUSED(fd);
+    UNUSED(offset);
+    UNUSED(whence);
+
+    ESP_LOGD(TAG, "lseek %ld", offset);
+
+    switch (whence) {
+    case SEEK_SET:
+    case SEEK_CUR:
+    case SEEK_END:
+        return 0;
+    default:
+        errno = EINVAL;
+        return -1;
+    }
+}
+
+static ssize_t vfs_null_read(int fd, void *data, size_t size)
+{
+    UNUSED(fd);
+    UNUSED(data);
+
+    ESP_LOGD(TAG, "read %u bytes", size);
+
+    if (FD_IN_RANGE(fd) && READABLE(g_fds, fd)) {
+        return 0; // EOF
+    }
+
+    errno = EBADF;
+    return -1;
+}
+
+static int vfs_null_pread(int fd, void *data, size_t size, off_t offset)
+{
+    UNUSED(fd);
+    UNUSED(data);
+    UNUSED(size);
+    UNUSED(offset);
+
+    errno = ESPIPE;
+    return -1;
+}
+
+static int vfs_null_pwrite(int fd, const void *data, size_t size, off_t offset)
+{
+    UNUSED(fd);
+    UNUSED(data);
+    UNUSED(size);
+    UNUSED(offset);
+
+    errno = ESPIPE;
+    return -1;
+}
+
+static int vfs_null_get_empty_fd(void)
+{
+    for (int i = 0; i < 32; i++) {
+        if (GET_FLAGS(g_fds, i) == VFS_NULL_CLOSED) {
+            return i;
+        }
+    }
+
+    return -1;
+}
+
+static int vfs_null_open(const char* path, int flags, int mode)
+{
+    UNUSED(mode);
+
+    ESP_LOGD(TAG, "open %s, flags %d", path, flags);
+
+    // Possibly check if the flags are valid
+
+    if (strcmp(path, "/") != 0) {
+        errno = ENOENT;
+        return -1;
+    }
+
+    int fd = vfs_null_get_empty_fd();
+    if (fd == -1) {
+        errno = EMFILE;
+        return -1;
+    }
+
+    if (flags & O_RDWR) {
+        SET_READABLE(g_fds, fd);
+        SET_WRITABLE(g_fds, fd);
+    } else if (flags & O_WRONLY) {
+        SET_WRITABLE(g_fds, fd);
+    } else if (flags & O_RDONLY) {
+        SET_READABLE(g_fds, fd);
+    } else {
+        errno = EINVAL;
+        return -1;
+    }
+
+    return fd;
+}
+
+static int vfs_null_close(int fd)
+{
+    if (!FD_IN_RANGE(fd)) {
+        errno = EBADF;
+        return -1;
+    }
+
+    SET_FLAGS(g_fds, fd, VFS_NULL_CLOSED);
+    return 0;
+}
+
+static int vfs_null_fstat(int fd, struct stat *st)
+{
+    if (!FD_IN_RANGE(fd)) {
+        errno = EBADF;
+        return -1;
+    }
+
+    memset(st, 0, sizeof(struct stat));
+    st->st_mode = S_IFCHR | 0666; // Special character device with read/write permissions for everyone
+    st->st_nlink = 1;
+    st->st_uid = 0;
+    st->st_gid = 0;
+    st->st_rdev = makedev(1, 3); // Null device (from Linux)
+
+    return 0;
+}
+
+#if CONFIG_VFS_SUPPORT_DIR
+
+static int vfs_null_stat(const char* path, struct stat *st)
+{
+    if (strcmp(path, "/") != 0) {
+        errno = ENOENT;
+        return -1;
+    }
+
+    memset(st, 0, sizeof(struct stat));
+    st->st_mode = S_IFCHR | 0666; // Special character device with read/write permissions for everyone
+    st->st_nlink = 1;
+    st->st_uid = 0;
+    st->st_gid = 0;
+    st->st_rdev = makedev(1, 3); // Null device (from Linux)
+
+    return 0;
+}
+
+#endif // CONFIG_VFS_SUPPORT_DIR
+
+static int vfs_null_fcntl(int fd, int cmd, int arg)
+{
+    UNUSED(arg);
+
+    if (!FD_IN_RANGE(fd)) {
+        errno = EBADF;
+        return -1;
+    }
+
+    switch (cmd) {
+    default:
+        errno = ENOSYS;
+        return -1;
+    }
+}
+
+static int vfs_null_ioctl(int fd, int cmd, va_list args)
+{
+    UNUSED(args);
+
+    if (!FD_IN_RANGE(fd)) {
+        errno = EBADF;
+        return -1;
+    }
+
+    switch (cmd) {
+    default:
+        errno = ENOSYS;
+        return -1;
+    }
+}
+
+static int vfs_null_fsync(int fd)
+{
+    if (!FD_IN_RANGE(fd)) {
+        errno = EBADF;
+        return -1;
+    }
+
+    return 0;
+}
+
+#if CONFIG_ESP_CONSOLE_NONE
+ESP_SYSTEM_INIT_FN(init_vfs_nullfs, CORE, BIT(0), 113)
+{
+    return esp_vfs_null_register();
+}
+#endif