samples/subsys/fs/littlefs: add a basic sample

Uses a littlefs file system to maintain a boot counter.  Also tests some
other functions.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>

samples/subsys/fs/littlefs/CMakeLists.txt

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+#
+# Copyright (c) 2019 Peter Bigot Consulting, LLC
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+cmake_minimum_required(VERSION 3.13.1)
+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(littlefs)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/subsys/fs/littlefs/Kconfig

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+# Copyright (c) 2019 Peter Bigot Consulting, LLC
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+config APP_WIPE_STORAGE
+	bool "Option to clear the flash area before mounting"
+	help
+	  Use this to force an existing file system to be created.
+
+source "$ZEPHYR_BASE/Kconfig"

samples/subsys/fs/littlefs/README.rst

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+.. _littlefs-sample:
+
+littlefs File System Sample Application
+#######################################
+
+Overview
+********
+
+This sample app demonstrates use of Zephyr's :ref:`file system API
+<file_system>` over `littlefs`_, using a file system with a file that
+counts the number of times the system has booted.  Other information
+about the file system is also displayed.
+
+.. _littlefs:
+   https://github.com/ARMmbed/littlefs
+
+Requirements
+************
+
+The partition labeled "storage" will be used for the file system; see
+:ref:`flash_partitions`.  If that area does not already have a
+compatible littlefs file system its contents will be replaced by an
+empty file system.  You will see diagnostics like this::
+
+   [00:00:00.010,192] <inf> littlefs: LittleFS version 2.0, disk version 2.0
+   [00:00:00.010,559] <err> littlefs: Corrupted dir pair at 0 1
+   [00:00:00.010,559] <wrn> littlefs: can't mount (LFS -84); formatting
+
+The error and warning are normal for a new file system.
+
+After the file system is mounted you'll also see::
+
+   [00:00:00.182,434] <inf> littlefs: filesystem mounted!
+   [00:00:00.867,034] <err> fs: failed get file or dir stat (-2)
+
+This error is also normal for Zephyr not finding a file (the boot count,
+in this case).
+
+Building and Running
+********************
+
+This example should work on any board that provides a "storage"
+partition.  Two tested board targets are described below.
+
+You can set ``CONFIG_APP_WIPE_STORAGE`` to force the file system to be
+recreated.
+
+NRF52840 Development Kit
+========================
+
+On this device the file system will be placed in the SOC flash.
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/subsys/fs/littlefs
+   :board: nrf52840_pca10056
+   :goals: build
+   :compact:
+
+Particle Xenon
+==============
+
+On this device the file system will be placed on the external SPI NOR
+flash memory.
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/subsys/fs/littlefs
+   :board: particle_xenon
+   :goals: build
+   :compact:

samples/subsys/fs/littlefs/boards/nrf52840_pca10056.conf

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+#
+# Copyright (c) 2019 Peter Bigot Consulting, LLC
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+# Need this when storage is on flash
+CONFIG_MPU_ALLOW_FLASH_WRITE=y
+
+# Need this when storage is on MX25R64
+CONFIG_SPI=y
+CONFIG_SPI_NOR=y
+CONFIG_SPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096

samples/subsys/fs/littlefs/boards/particle_xenon.conf

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+#
+# Copyright (c) 2019 Peter Bigot Consulting, LLC
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+CONFIG_SPI=y
+CONFIG_SPI_NOR=y
+CONFIG_SPI_NOR_FLASH_LAYOUT_PAGE_SIZE=4096

samples/subsys/fs/littlefs/particle_xenon.overlay

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+/*
+ * Copyright (c) 2019 Peter Bigot Consulting, LLC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/delete-node/ &storage_partition;
+
+&mx25l32 {
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		/* This is the littlefs v1 file system pre-installed
+		 * by Particle.
+		 */
+		littlefs_partition: partition@0 {
+			label = "littlefs";
+			reg = <0x00000000 0x00200000>;
+		};
+		/* A 16 KiBy partition to use for the test. */
+		storage_partition: partition@200000 {
+			label = "storage";
+			reg = <0x00200000 0x00004000>;
+		};
+		/* A bigger partition for something else. */
+		partition@220000 {
+			label = "scratch";
+			reg = <0x00204000 0x001fc000>;
+		};
+	};
+};

samples/subsys/fs/littlefs/prj.conf

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+#
+# Copyright (c) 2019 Peter Bigot Consulting, LLC
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+# Optionally force the file system to be recreated
+#CONFIG_APP_WIPE_STORAGE=y
+
+# fs_dirent structures are big.
+CONFIG_MAIN_STACK_SIZE=2048
+
+CONFIG_LOG=y
+#CONFIG_FS_LOG_LEVEL_DBG=y
+
+CONFIG_FLASH=y
+CONFIG_FLASH_MAP=y
+CONFIG_FLASH_PAGE_LAYOUT=y
+
+CONFIG_FILE_SYSTEM=y
+CONFIG_FILE_SYSTEM_LITTLEFS=y

samples/subsys/fs/littlefs/sample.yaml

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+sample:
+  name: littlefs filesystem sample
+tests:
+  sample.subsys.fs.littlefs:
+    build_only: true
+    platform_whitelist: nrf52840_pca10056 particle_xenon
+    tags: filesystem

samples/subsys/fs/littlefs/src/main.c

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+/*
+ * Copyright (c) 2019 Peter Bigot Consulting, LLC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/* Sample which uses the filesystem API with littlefs */
+
+#include <stdio.h>
+
+#include <zephyr.h>
+#include <device.h>
+#include <fs/fs.h>
+#include <fs/littlefs.h>
+#include <storage/flash_map.h>
+
+/* Matches LFS_NAME_MAX */
+#define MAX_PATH_LEN 255
+
+static struct fs_littlefs lfs_storage;
+static struct fs_mount_t lfs_storage_mnt = {
+	.type = FS_LITTLEFS,
+	.fs_data = &lfs_storage,
+	.storage_dev = (void *)DT_FLASH_AREA_STORAGE_ID,
+	.mnt_point = "/lfs",
+};
+
+void main(void)
+{
+	struct fs_mount_t *mp = &lfs_storage_mnt;
+	unsigned int id = (uintptr_t)mp->storage_dev;
+	char fname[MAX_PATH_LEN];
+	struct fs_statvfs sbuf;
+	const struct flash_area *pfa;
+	int rc;
+
+	snprintf(fname, sizeof(fname), "%s/boot_count", mp->mnt_point);
+
+	rc = flash_area_open(id, &pfa);
+	if (rc < 0) {
+		printk("FAIL: unable to find flash area %u: %d\n",
+		       id, rc);
+		return;
+	}
+
+	printk("Area %u at 0x%x on %s for %u bytes\n",
+	       id, (unsigned int)pfa->fa_off, pfa->fa_dev_name,
+	       (unsigned int)pfa->fa_size);
+
+	/* Optional wipe flash contents */
+	if (IS_ENABLED(CONFIG_APP_WIPE_STORAGE)) {
+		printk("Erasing flash area ... ");
+		rc = flash_area_erase(pfa, 0, pfa->fa_size);
+		printk("%d\n", rc);
+		flash_area_close(pfa);
+	}
+
+	rc = fs_mount(mp);
+	if (rc < 0) {
+		printk("FAIL: mount id %u at %s: %d\n",
+		       (unsigned int)mp->storage_dev, mp->mnt_point,
+		       rc);
+		return;
+	}
+	printk("%s mount: %d\n", mp->mnt_point, rc);
+
+	rc = fs_statvfs(mp->mnt_point, &sbuf);
+	if (rc < 0) {
+		printk("FAIL: statvfs: %d\n", rc);
+		goto out;
+	}
+
+	printk("%s: bsize = %lu ; frsize = %lu ;"
+	       " blocks = %lu ; bfree = %lu\n",
+	       mp->mnt_point,
+	       sbuf.f_bsize, sbuf.f_frsize,
+	       sbuf.f_blocks, sbuf.f_bfree);
+
+	struct fs_dirent dirent;
+
+	rc = fs_stat(fname, &dirent);
+	printk("%s stat: %d\n", fname, rc);
+	if (rc >= 0) {
+		printk("\tfn '%s' siz %u\n", dirent.name, dirent.size);
+	}
+
+	struct fs_file_t file;
+
+	rc = fs_open(&file, fname);
+	if (rc < 0) {
+		printk("FAIL: open %s: %d\n", fname, rc);
+		goto out;
+	}
+
+	u32_t boot_count = 0;
+
+	if (rc >= 0) {
+		rc = fs_read(&file, &boot_count, sizeof(boot_count));
+		printk("%s read count %u: %d\n", fname, boot_count, rc);
+		rc = fs_seek(&file, 0, FS_SEEK_SET);
+		printk("%s seek start: %d\n", fname, rc);
+
+	}
+
+	boot_count += 1;
+	rc = fs_write(&file, &boot_count, sizeof(boot_count));
+	printk("%s write new boot count %u: %d\n", fname,
+	       boot_count, rc);
+
+	rc = fs_close(&file);
+	printk("%s close: %d\n", fname, rc);
+
+	struct fs_dir_t dir = { 0 };
+
+	rc = fs_opendir(&dir, mp->mnt_point);
+	printk("%s opendir: %d\n", mp->mnt_point, rc);
+
+	while (rc >= 0) {
+		struct fs_dirent ent = { 0 };
+
+		rc = fs_readdir(&dir, &ent);
+		if (rc < 0) {
+			break;
+		}
+		if (ent.name[0] == 0) {
+			printk("End of files\n");
+			break;
+		}
+		printk("  %c %u %s\n",
+		       (ent.type == FS_DIR_ENTRY_FILE) ? 'F' : 'D',
+		       ent.size,
+		       ent.name);
+	}
+
+	(void)fs_closedir(&dir);
+
+out:
+	rc = fs_unmount(mp);
+	printk("%s unmount: %d\n", mp->mnt_point, rc);
+}