feat(storage/fatfs): restructure fatfsgen example

examples/storage/fatfs/fatfsgen/CMakeLists.txt

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+# The following lines of boilerplate have to be in your project's CMakeLists
+# in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.16)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(fatfsgen)

examples/storage/fatfs/fatfsgen/README.md

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+| Supported Targets | ESP32 | ESP32-C2 | ESP32-C3 | ESP32-C5 | ESP32-C6 | ESP32-C61 | ESP32-H2 | ESP32-P4 | ESP32-S2 | ESP32-S3 |
+| ----------------- | ----- | -------- | -------- | -------- | -------- | --------- | -------- | -------- | -------- | -------- |
+
+# FATFS partition generation example
+
+(See the README.md file in the upper level 'examples' directory for more information about examples.)
+
+This example demonstrates how to use the FATFS partition
+generation tool [fatfsgen.py](../../../components/fatfs/fatfsgen.py) to automatically create a FATFS
+filesystem image from the contents of a host folder during build, with an option of
+automatically flashing the created image on invocation of `idf.py -p PORT flash`.
+Beware that the minimal required size of the flash is 4 MB.
+You can specify using menuconfig weather example will use read-only or read-write mode. The default option is read-write mode.
+To change it just use menuconfig:
+
+```shell
+idf.py menuconfig
+```
+
+Then select `Example Configuration` a chose `Mode for generated FATFS image` either `Read-Write Mode` or `Read-Only Mode`.
+`Read-Only` option indicates generating raw fatfs image without wear levelling support.
+On the other hand, for `Read-Write` the generated fatfs image will support wear levelling thus can be mounted in read-write mode.
+
+
+The following gives an overview of the example:
+
+1. There is a directory `fatfs_long_name_image` from which the FATFS filesystem image will be created.
+
+2. Based on the RO/RW configuration either `fatfs_create_rawflash_image` or `fatfs_create_spiflash_image` respectively,
+is used to specify that a FATFS image should be created during build for the `storage` partition.
+For CMake, it is called from [the main component's CMakeLists.txt](./main/CMakeLists.txt).
+`FLASH_IN_PROJECT` specifies that the created image
+should be flashed on invocation of `idf.py -p PORT flash` together with app, bootloader, partition table, etc.
+The image is created on the example's build directory with the output filename `storage.bin`.
+
+3. Upon invocation of `idf.py -p PORT flash monitor`, application loads and
+finds there is already a valid FATFS filesystem in the `storage` partition with files same as those in `fatfs_image` directory. The application is then
+able to read those files.
+
+## How to use example
+
+### Build and flash
+
+To run the example, type the following command:
+
+```CMake
+# CMake
+idf.py -p PORT flash monitor
+```
+
+(To exit the serial monitor, type ``Ctrl-]``.)
+
+See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
+
+## Example output
+
+Here is the example's console output:
+
+```
+...
+I (322) example: Mounting FAT filesystem
+I (332) example: Reading file
+I (332) example: Read from file: 'this is test'
+I (332) example: Unmounting FAT filesystem
+I (342) example: Done
+```
+
+The logic of the example is contained in a [single source file](./main/fatfsgen_example_main.c),
+and it should be relatively simple to match points in its execution with the log outputs above.

examples/storage/fatfs/fatfsgen/fatfs_image/hellolongname.txt

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+This is generated on the host; long name it has

examples/storage/fatfs/fatfsgen/fatfs_image/subdir/testlongfilenames.txt

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+this is test; long name it has

examples/storage/fatfs/fatfsgen/main/CMakeLists.txt

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+idf_component_register(SRCS "fatfsgen_example_main.c"
+                    INCLUDE_DIRS ".")
+
+# Create a FATFS image from the contents of the 'fatfs_long_name_image' directory
+# that fits the partition named 'storage'. FLASH_IN_PROJECT indicates that
+# the generated image should be flashed when the entire project is flashed to
+# the target with 'idf.py -p PORT flash'.
+# If read-only mode is set (CONFIG_EXAMPLE_FATFS_MODE_READ_ONLY)
+# the generated image will be raw without wear levelling support.
+# Otherwise it will support wear levelling and thus enable read-write mounting of the image in the device.
+
+set(image ../fatfs_image)
+
+if(CONFIG_EXAMPLE_FATFS_MODE_READ_ONLY)
+    fatfs_create_rawflash_image(storage ${image} FLASH_IN_PROJECT PRESERVE_TIME)
+else()
+    fatfs_create_spiflash_image(storage ${image} FLASH_IN_PROJECT PRESERVE_TIME)
+endif()

examples/storage/fatfs/fatfsgen/main/Kconfig.projbuild

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+menu "Example Configuration"
+
+    config EXAMPLE_FATFS_MODE_READ_ONLY
+        bool "Read only mode for generated FATFS image"
+        default y
+        help
+            If read-only mode is set, the generated fatfs image will be raw (without wear levelling support).
+            Otherwise it will support wear levelling that enables read-write mounting.
+
+endmenu

examples/storage/fatfs/fatfsgen/main/fatfsgen_example_main.c

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+/*
+ * SPDX-FileCopyrightText: 2021-2024 Espressif Systems (Shanghai) CO LTD
+ *
+ * SPDX-License-Identifier: Unlicense OR CC0-1.0
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "esp_vfs.h"
+#include "esp_vfs_fat.h"
+#include "esp_err.h"
+#include "sdkconfig.h"
+
+static const char *TAG = "example";
+
+// Mount path for the partition
+const char *base_path = "/spiflash";
+
+
+void app_main(void)
+{
+    // To mount device we need name of device partition, define base_path
+    // and allow format partition in case if it is new one and was not formatted before
+    const esp_vfs_fat_mount_config_t mount_config = {
+            .max_files = 4,
+            .format_if_mount_failed = false,
+            .allocation_unit_size = CONFIG_WL_SECTOR_SIZE,
+            .use_one_fat = false,
+    };
+
+#if CONFIG_EXAMPLE_FATFS_MODE_READ_ONLY
+    ESP_LOGI(TAG, "Mounting FAT filesystem in read-only mode");
+    esp_err_t err = esp_vfs_fat_spiflash_mount_ro(base_path, "storage", &mount_config);
+#else
+    ESP_LOGI(TAG, "Mounting FAT filesystem in read/write mode");
+    static wl_handle_t wl_handle = WL_INVALID_HANDLE;
+    esp_err_t err = esp_vfs_fat_spiflash_mount_rw_wl(base_path, "storage", &mount_config, &wl_handle);
+#endif
+
+    if (err != ESP_OK) {
+        ESP_LOGE(TAG, "Failed to mount FATFS (%s)", esp_err_to_name(err));
+        return;
+    }
+
+    char line[128];
+
+    FILE *f;
+    char *pos;
+    ESP_LOGI(TAG, "Reading file");
+
+    const char *host_filename1 = "/spiflash/subdir/testlongfilenames.txt";
+
+    struct stat info;
+    struct tm timeinfo;
+    char buffer[32];
+
+    if(stat(host_filename1, &info) < 0){
+        ESP_LOGE(TAG, "Failed to read file stats");
+        return;
+    }
+    localtime_r(&info.st_mtime, &timeinfo);
+    strftime(buffer, sizeof(buffer), "%Y-%m-%d", &timeinfo);
+
+    ESP_LOGI(TAG, "The file '%s' was modified at date: %s", host_filename1, buffer);
+
+
+    f = fopen(host_filename1, "rb");
+    if (f == NULL) {
+        ESP_LOGE(TAG, "Failed to open file for reading");
+        return;
+    }
+    fgets(line, sizeof(line), f);
+    fclose(f);
+    // strip newline
+    pos = strchr(line, '\n');
+    if (pos) {
+        *pos = '\0';
+    }
+    ESP_LOGI(TAG, "Read from file: '%s'", line);
+
+    // Unmount FATFS
+    ESP_LOGI(TAG, "Unmounting FAT filesystem");
+
+#if CONFIG_EXAMPLE_FATFS_MODE_READ_ONLY
+    ESP_ERROR_CHECK(esp_vfs_fat_spiflash_unmount_ro(base_path, "storage"));
+#else
+    ESP_ERROR_CHECK(esp_vfs_fat_spiflash_unmount_rw_wl(base_path, wl_handle));
+#endif
+
+    ESP_LOGI(TAG, "Done");
+}

examples/storage/fatfs/fatfsgen/partitions_example.csv

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+# Name,   Type, SubType, Offset,  Size,    Flags
+# Note: if you have increased the bootloader size, make sure to update the offsets to avoid overlap
+nvs,      data, nvs,     0x9000,  0x6000,
+phy_init, data, phy,     0xf000,  0x1000,
+factory,  app,  factory, 0x10000, 1M,
+storage,  data, fat,     ,        1M,

examples/storage/fatfs/fatfsgen/pytest_fatfs_fatfsgen_example.py

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+# SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
+# SPDX-License-Identifier: Unlicense OR CC0-1.0
+import os
+import re
+from datetime import datetime
+from typing import List
+
+import pytest
+from pytest_embedded import Dut
+
+idf_path = os.environ['IDF_PATH']  # get value of IDF_PATH from environment
+parttool_dir = os.path.join(idf_path, 'components', 'partition_table')
+
+
+@pytest.mark.esp32
+@pytest.mark.generic
+@pytest.mark.parametrize('config', ['test_read_only_partition_gen_ln',
+                                    'test_read_write_partition_gen_ln',
+                                    ], indirect=True)
+def test_examples_fatfs_fatfsgen(config: str, dut: Dut) -> None:
+    # Expects list of strings sequentially
+    def expect_all(msg_list: List[str], to: int) -> None:
+        for msg in msg_list:
+            dut.expect(msg, timeout=to)
+
+    # Expects prefix string followed by date in the format 'yyyy-mm-dd'
+    def expect_date(prefix: str, to: int) -> datetime:
+        expect_str = prefix + '(\\d+)-(\\d+)-(\\d+)'
+        match_ = dut.expect(re.compile(str.encode(expect_str)), timeout=to)
+        year_ = int(match_[1].decode())
+        month_ = int(match_[2].decode())
+        day_ = int(match_[3].decode())
+        return datetime(year_, month_, day_)
+
+    # Calculates absolute difference in days between date_reference and date_actual.
+    # Raises exception if difference exceeds tolerance
+    def evaluate_dates(date_reference: datetime, date_actual: datetime, days_tolerance: int) -> None:
+        td = date_actual - date_reference
+        if abs(td.days) > days_tolerance:
+            raise Exception(f'Too big date difference. Actual: {date_actual}, reference: {date_reference}, tolerance: {days_tolerance} day(s)')
+
+    # Expect timeout
+    timeout = 20
+
+    # We tolerate 30 days difference between actual file creation and date when test was executed.
+    tolerance = 30
+    filename = 'sublongnames/testlongfilenames.txt'
+    date_ref = datetime.today()
+
+    if config in ['test_read_write_partition_gen']:
+        filename_expected = f'/spiflash/{filename}'
+        expect_all(['example: Mounting FAT filesystem',
+                    'example: Opening file',
+                    'example: File written',
+                    'example: Reading file',
+                    'example: Read from file: \'This is written by the device\'',
+                    'example: Reading file'], timeout)
+        date_act = expect_date(f'The file \'{filename_expected}\' was modified at date: ', timeout)
+        evaluate_dates(date_ref, date_act, tolerance)
+        expect_all(['example: Read from file: \'This is generated on the host\'',
+                    'example: Unmounting FAT filesystem',
+                    'example: Done'], timeout)
+
+    elif config in ['test_read_only_partition_gen']:
+        filename_expected = f'/spiflash/{filename}'
+        expect_all(['example: Mounting FAT filesystem',
+                    'example: Reading file'], timeout)
+        date_act = expect_date(f'The file \'{filename_expected}\' was modified at date: ', timeout)
+        evaluate_dates(date_ref, date_act, tolerance)
+        expect_all(['example: Read from file: \'this is test\'',
+                    'example: Unmounting FAT filesystem',
+                    'example: Done'], timeout)

examples/storage/fatfs/fatfsgen/sdkconfig.ci.test_read_only_partition_gen_ln

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+CONFIG_EXAMPLE_FATFS_MODE_READ_ONLY=y
+CONFIG_FATFS_LFN_HEAP=y
+CONFIG_FATFS_LFN_NONE=n
+CONFIG_FATFS_LFN_STACK=n

examples/storage/fatfs/fatfsgen/sdkconfig.ci.test_read_write_partition_gen_ln

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+CONFIG_EXAMPLE_FATFS_MODE_READ_ONLY=n
+CONFIG_FATFS_LFN_HEAP=y
+CONFIG_FATFS_LFN_NONE=n
+CONFIG_FATFS_LFN_STACK=n

examples/storage/fatfs/fatfsgen/sdkconfig.defaults

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+CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
+CONFIG_PARTITION_TABLE_CUSTOM=y
+CONFIG_PARTITION_TABLE_CUSTOM_FILENAME="partitions_example.csv"
+CONFIG_FATFS_LFN_HEAP=y