samples: usb: add ffatdisk sample

This sample has two volumes, FAT16 and FAT32, exported via
new USB device MSC support.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>

samples/subsys/usb/ffat/CMakeLists.txt

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+# Copyright (c) 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(ffat)
+
+include(${ZEPHYR_BASE}/samples/subsys/usb/common/common.cmake)
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/subsys/usb/ffat/Kconfig

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+# Copyright (c) 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+# Source common USB sample options used to initialize new experimental USB
+# device stack. The scope of these options is limited to USB samples in project
+# tree, you cannot use them in your own application.
+source "samples/subsys/usb/common/Kconfig.sample_usbd"
+
+source "Kconfig.zephyr"

samples/subsys/usb/ffat/README.rst

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+.. zephyr:code-sample:: usb-ffat
+   :name: USB FFAT
+   :relevant-api: usbd_api usbd_msc_device
+
+   Expose a FFAT disk over USB using the USB Mass Storage Class implementation.
+
+Overview
+********
+
+This sample application demonstrates the FFAT disk implementation using the new
+experimental USB device stack. The sample has two FFAT disks that emulate FAT16
+and FAT32 file system formatted disks. There is no real disk or file system
+behind them. The two disks emulate FAT formatted disks at runtime. When mounted
+on the host side, you will find three files on the FFAT16 disk and two files on
+the FFAT32 disk. You can read and write to the binary files; the text files are
+read-only. Writing to a file means that for each block written to the disk, a
+callback is invoked on the Zephyr side that can be used, for example, to update
+firmware or load something into the device running the Zephyr RTOS.
+
+Requirements
+************
+
+This project requires an experimental USB device driver (UDC API).
+
+Building and Running
+********************
+
+This sample can be built for multiple boards, in this example we will build it
+for the nRF52840DK board:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/subsys/usb/ffat
+   :board: nrf52840dk/nrf52840
+   :goals: build flash
+   :compact:

samples/subsys/usb/ffat/app.overlay

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+/*
+ * Copyright (c) 2023 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	ffatdisk0 {
+		compatible = "zephyr,ffat-disk";
+		disk-name = "FFAT16";
+		sector-size = <512>;
+		sector-count = <8192>;
+		sector-per-cluster = <1>;
+	};
+
+	ffatdisk1 {
+		compatible = "zephyr,ffat32-disk", "zephyr,ffat-disk";
+		disk-name = "FFAT32";
+		sector-size = <512>;
+		sector-count = <7744512>;
+		sector-per-cluster = <8>;
+	};
+};

samples/subsys/usb/ffat/prj.conf

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+CONFIG_USB_DEVICE_STACK_NEXT=y
+
+CONFIG_STDOUT_CONSOLE=y
+CONFIG_USBD_MSC_CLASS=y
+CONFIG_USBD_MSC_LUNS_PER_INSTANCE=2
+
+CONFIG_LOG=y
+CONFIG_USBD_LOG_LEVEL_WRN=y
+CONFIG_UDC_DRIVER_LOG_LEVEL_WRN=y
+
+CONFIG_MAIN_STACK_SIZE=2048

samples/subsys/usb/ffat/sample.yaml

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+sample:
+  name: USB FFAT sample
+common:
+  depends_on:
+    - usbd
+  integration_platforms:
+    - nrf52840dk/nrf52840
+    - nrf54h20dk/nrf54h20/cpuapp
+    - frdm_k64f
+    - nucleo_f413zh
+    - mimxrt1060_evk
+tests:
+  sample.usbd.ffat:
+    tags: usb filesystem

samples/subsys/usb/ffat/src/main.c

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+/*
+ * Copyright (c) 2023 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <sample_usbd.h>
+
+#include <stdint.h>
+#include <version.h>
+
+#include <zephyr/kernel.h>
+#include <zephyr/sys/byteorder.h>
+#include <zephyr/usb/usbd.h>
+#include <zephyr/usb/class/usbd_msc.h>
+#include <zephyr/storage/ffatdisk.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(main, LOG_LEVEL_INF);
+
+#ifdef BUILD_VERSION
+#define BANNER_VERSION STRINGIFY(BUILD_VERSION)
+#else
+#define BANNER_VERSION KERNEL_VERSION_STRING
+#endif
+
+const char txt_info_file[] =
+	"Zephyr RTOS\n"
+	"Build " BANNER_VERSION "\n"
+	"Board " CONFIG_BOARD "\n"
+	"Arch "CONFIG_ARCH "\n";
+
+const char html_info_file[] =
+	"<!DOCTYPE html>\n"
+	"<html>\n"
+	"<head>\n"
+	"<style>\n"
+	"body {\n"
+		"background: #AF7FE4;\n"
+	"}\n"
+	".content {\n"
+		"max-width: 480px;\n"
+		"background: #F0F2F4;\n"
+		"margin: auto;\n"
+		"padding: 16px;\n"
+	"}\n"
+	"</style>\n"
+	"</head>\n"
+	"<body>\n"
+	"<div class=\"content\">\n"
+		"<h1>FFAT sample</h1>\n"
+		"<p><a href=\"https://www.zephyrproject.org/\">zephyrproject.org</a></p>\n"
+	"</div>\n"
+	"</body>\n"
+	"</html>\n";
+
+struct binfile {
+	uint32_t s_tag;
+	uint32_t b_num;
+	uint8_t reserved[500];
+	uint32_t e_tag;
+} __packed;
+
+BUILD_ASSERT(sizeof(struct binfile) == 512U);
+
+static int infofile_rd_cb(struct ffat_file *const f, const uint32_t sector,
+			  uint8_t *const buf, const uint32_t size)
+{
+	size_t f_off = size * sector;
+
+	if (f->size > f_off) {
+		size_t len = MIN(f->size - f_off, size);
+
+		memcpy(buf, (uint8_t *)f->priv + f_off, len);
+		LOG_DBG("Read %u bytes, sector %u file offset %zu, f->size %zu",
+			len, sector, f_off, f->size);
+	}
+
+	return 0;
+}
+
+static int binfile_rd_cb(struct ffat_file *const f, const uint32_t sector,
+			 uint8_t *const buf, const uint32_t size)
+{
+	size_t f_off = size * sector;
+
+	if (f->size > f_off) {
+		size_t len = MIN(f->size - f_off, size);
+		struct binfile *test = (void *)buf;
+
+		test->s_tag = sys_cpu_to_le32(0xDECAFBAD);
+		test->b_num = sys_cpu_to_le32(sector);
+		test->e_tag = sys_cpu_to_le32(0xDEADDA7A);
+
+		LOG_DBG("Read %u bytes, sector %u file offset %zu, f->size %zu",
+			len, sector, f_off, f->size);
+	}
+
+	return 0;
+}
+
+static int binfile_wr_cb(struct ffat_file *const f, const uint32_t sector,
+			 const uint8_t *const buf, const uint32_t size)
+{
+	size_t f_off = size * sector;
+
+	if (f->size > f_off) {
+		size_t len = MIN(f->size - f_off, size);
+
+		LOG_DBG("Write %u bytes, sector %u file offset %zu, f->size %zu",
+			len, sector, f_off, f->size);
+	}
+
+	return 0;
+}
+
+FFAT_FILE_DEFINE(readme, "FFAT16", "README  TXT", sizeof(txt_info_file),
+		 infofile_rd_cb, NULL, txt_info_file);
+FFAT_FILE_DEFINE(html, "FFAT16", "INDEX   HTM", sizeof(html_info_file),
+		 infofile_rd_cb, NULL, html_info_file);
+FFAT_FILE_DEFINE(bin, "FFAT16", "FOOBAZ  BIN", 32768U,
+		 binfile_rd_cb, binfile_wr_cb, NULL);
+
+FFAT_FILE_DEFINE(readme32, "FFAT32", "README  TXT", sizeof(txt_info_file),
+		 infofile_rd_cb, NULL, txt_info_file);
+FFAT_FILE_DEFINE(big, "FFAT32", "FOOBAZ  BIN", 66051072UL,
+		 binfile_rd_cb, binfile_wr_cb, NULL);
+
+USBD_DEFINE_MSC_LUN(ffat16, "FFAT16", "Zephyr", "FFAT16", "0.00");
+USBD_DEFINE_MSC_LUN(ffat32, "FFAT32", "Zephyr", "FFAT32", "0.00");
+
+int main(void)
+{
+	struct usbd_context *sample_usbd;
+	int ret;
+
+	sample_usbd = sample_usbd_init_device(NULL);
+	if (sample_usbd == NULL) {
+		LOG_ERR("Failed to initialize USB device");
+		return -ENODEV;
+	}
+
+	ret = usbd_enable(sample_usbd);
+	if (ret) {
+		LOG_ERR("Failed to enable device support");
+		return ret;
+	}
+
+	LOG_INF("FFAT sample is ready.");
+
+	return 0;
+}