modules/fatfs: Move FATFS Zephyr specific code and cmake

The code moves Zephyr specific code and CMakeLists.txt
under modules/fatfs/.

The commit also adds zephyr_fatfs_config.h header file, that
is now used to override FF_ options of ffconf.h file within
fatfs repository.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>

modules/fatfs/CMakeLists.txt

@@ -0,0 +1,26 @@
+if(CONFIG_FAT_FILESYSTEM_ELM)
+  add_library(ELMFAT INTERFACE)
+
+  target_include_directories(ELMFAT INTERFACE
+    ${CMAKE_CURRENT_SOURCE_DIR}
+    ${ZEPHYR_FATFS_MODULE_DIR}/include
+  )
+
+  target_compile_definitions(ELMFAT INTERFACE
+    ZEPHYR_CONFIG_OVERRIDE=zephyr_fatfs_config.h
+  )
+
+  zephyr_library()
+  zephyr_library_sources(
+    ${ZEPHYR_FATFS_MODULE_DIR}/ff.c
+    zfs_diskio.c
+    )
+
+  zephyr_library_sources_ifdef(CONFIG_FS_FATFS_LFN
+    ${ZEPHYR_FATFS_MODULE_DIR}/option/ffunicode.c
+    ${ZEPHYR_FATFS_MODULE_DIR}/option/ffsystem.c
+  )
+
+  zephyr_library_link_libraries(ELMFAT)
+  target_link_libraries(ELMFAT INTERFACE zephyr_interface)
+endif()

modules/fatfs/Kconfig

@@ -0,0 +1,8 @@
+# Copyright (c) 2022 Nordic Semiconductor ASA
+# SPDX-License-Identifier: Apache-2.0
+
+config ZEPHYR_FATFSFS_MODULE
+	bool
+
+# Configuration of ELM FAT is found in subsys/fs/Kconfig.fatfs for historic
+# reasons.

modules/fatfs/zephyr_fatfs_config.h

@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2022 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#if FFCONF_DEF != 86631
+#error "Configuration version mismatch"
+#endif
+
+/*
+ * Overrides of FF_ options from ffconf.h
+ */
+#if defined(CONFIG_FS_FATFS_READ_ONLY)
+#undef FF_FS_READONLY
+#define FF_FS_READONLY	CONFIG_FS_FATFS_READ_ONLY
+#endif /* defined(CONFIG_FS_FATFS_READ_ONLY) */
+
+#if defined(CONFIG_FS_FATFS_MKFS)
+#undef FF_USE_MKFS
+#define FF_USE_MKFS	CONFIG_FS_FATFS_MKFS
+#else
+/* Note that by default the ffconf.h disables MKFS */
+#undef FF_USE_MKFS
+#define FF_USE_MKFS 1
+#endif /* defined(CONFIG_FS_FATFS_MKFS) */
+
+#if defined(CONFIG_FS_FATFS_CODEPAGE)
+#undef FF_CODE_PAGE
+#define FF_CODE_PAGE	CONFIG_FS_FATFS_CODEPAGE
+#else
+/* Note that default value, in ffconf.h, for FF_CODE_PAGE is 932 */
+#undef FF_CODE_PAGE
+#define FF_CODE_PAGE 437
+#endif /* defined(CONFIG_FS_FATFS_CODEPAGE) */
+
+#if defined(CONFIG_FS_FATFS_LFN)
+#undef FF_USE_LFN
+#if CONFIG_FS_FATFS_LFN_MODE_BSS
+#define	FF_USE_LFN	1
+#elif CONFIG_FS_FATFS_LFN_MODE_STACK
+#define	FF_USE_LFN	2
+#elif CONFIG_FS_FATFS_LFN_MODE_HEAP
+#define	FF_USE_LFN	3
+#else
+#error Invalid LFN buffer location
+#endif
+#endif /* defined(CONFIG_FS_FATFS_LFN) */
+
+#if defined(CONFIG_FS_FATFS_MAX_LFN)
+#undef FF_MAX_LFN
+#define	FF_MAX_LFN	CONFIG_FS_FATFS_MAX_LFN
+#endif /* defined(CONFIG_FS_FATFS_MAX_LFN) */
+
+#if defined(CONFIG_FS_FATFS_MAX_SS)
+#undef FF_MAX_SS
+#define FF_MAX_SS		CONFIG_FS_FATFS_MAX_SS
+#endif /* defined(CONFIG_FS_FATFS_MAX_SS) */
+
+#if defined(CONFIG_FS_FATFS_EXFAT)
+#undef FF_FS_EXFAT
+#define FF_FS_EXFAT		CONFIG_FS_FATFS_EXFAT
+#endif /* defined(CONFIG_FS_FATFS_EXFAT) */
+
+/*
+ * These options are override from default values, but have no Kconfig
+ * options.
+ */
+#undef FF_FS_TINY
+#define FF_FS_TINY 1
+
+#undef FF_FS_NORTC
+#define FF_FS_NORTC 1
+
+/* Zephyr uses FF_VOLUME_STRS */
+#undef FF_STR_VOLUME_ID
+#define FF_STR_VOLUME_ID 1
+
+/* By default FF_STR_VOLUME_ID in ffconf.h is 0, which means that
+ * FF_VOLUME_STRS is not used. Zephyr uses FF_VOLUME_STRS, which
+ * by default holds 8 possible strings representing mount points,
+ * and FF_VOLUMES needs to reflect that, which means that dolt
+ * value of 1 is overridden here with 8.
+ */
+#undef FF_VOLUMES
+#define FF_VOLUMES 8
+
+/*
+ * Options provided below have been added to ELM FAT source code to
+ * support Zephyr specific features, and are not part of ffconf.h.
+ */
+/*
+ * The FS_FATFS_WINDOW_ALIGNMENT is used to align win buffer of FATFS structure
+ * to allow more optimal use with MCUs that require specific bufer alignment
+ * for DMA to work.
+ */
+#if defined(CONFIG_FS_FATFS_WINDOW_ALIGNMENT)
+#define FS_FATFS_WINDOW_ALIGNMENT	CONFIG_FS_FATFS_WINDOW_ALIGNMENT
+#else
+#define FS_FATFS_WINDOW_ALIGNMENT	1
+#endif /* defined(CONFIG_FS_FATFS_WINDOW_ALIGNMENT) */

modules/fatfs/zfs_diskio.c

@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2018-2021 Zephyr contributors
+ * Copyright (c) 2022 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+/* The file is based on template file by (C)ChaN, 2019, as
+ * available from FAT FS module source:
+ * https://github.com/zephyrproject-rtos/fatfs/blob/master/diskio.c
+ * and has been previously avaialble from directory for that module
+ * under name zfs_diskio.c.
+ */
+#include <ff.h>
+#include <diskio.h>	/* FatFs lower layer API */
+#include <zephyr/storage/disk_access.h>
+
+static const char * const pdrv_str[] = {FF_VOLUME_STRS};
+
+/* Get Drive Status */
+DSTATUS disk_status(BYTE pdrv)
+{
+	__ASSERT(pdrv < ARRAY_SIZE(pdrv_str), "pdrv out-of-range\n");
+
+	if (disk_access_status(pdrv_str[pdrv]) != 0) {
+		return STA_NOINIT;
+	} else {
+		return RES_OK;
+	}
+}
+
+/* Initialize a Drive */
+DSTATUS disk_initialize(BYTE pdrv)
+{
+	__ASSERT(pdrv < ARRAY_SIZE(pdrv_str), "pdrv out-of-range\n");
+
+	if (disk_access_init(pdrv_str[pdrv]) != 0) {
+		return STA_NOINIT;
+	} else {
+		return RES_OK;
+	}
+}
+
+/* Read Sector(s) */
+DRESULT disk_read(BYTE pdrv, BYTE *buff, DWORD sector, UINT count)
+{
+	__ASSERT(pdrv < ARRAY_SIZE(pdrv_str), "pdrv out-of-range\n");
+
+	if (disk_access_read(pdrv_str[pdrv], buff, sector, count) != 0) {
+		return RES_ERROR;
+	} else {
+		return RES_OK;
+	}
+
+}
+
+/* Write Sector(s) */
+DRESULT disk_write(BYTE pdrv, const BYTE *buff, DWORD sector, UINT count)
+{
+	__ASSERT(pdrv < ARRAY_SIZE(pdrv_str), "pdrv out-of-range\n");
+
+	if (disk_access_write(pdrv_str[pdrv], buff, sector, count) != 0) {
+		return RES_ERROR;
+	} else {
+		return RES_OK;
+	}
+}
+
+/* Miscellaneous Functions */
+DRESULT disk_ioctl(BYTE pdrv, BYTE cmd, void *buff)
+{
+	int ret = RES_OK;
+	uint32_t sector_size = 0;
+
+	__ASSERT(pdrv < ARRAY_SIZE(pdrv_str), "pdrv out-of-range\n");
+
+	switch (cmd) {
+	case CTRL_SYNC:
+		if (disk_access_ioctl(pdrv_str[pdrv],
+				DISK_IOCTL_CTRL_SYNC, buff) != 0) {
+			ret = RES_ERROR;
+		}
+		break;
+
+	case GET_SECTOR_COUNT:
+		if (disk_access_ioctl(pdrv_str[pdrv],
+				DISK_IOCTL_GET_SECTOR_COUNT, buff) != 0) {
+			ret = RES_ERROR;
+		}
+		break;
+
+	case GET_SECTOR_SIZE:
+		/* Zephyr's DISK_IOCTL_GET_SECTOR_SIZE returns sector size as a
+		 * 32-bit number while FatFS's GET_SECTOR_SIZE is supposed to
+		 * return a 16-bit number.
+		 */
+		if ((disk_access_ioctl(pdrv_str[pdrv],
+				DISK_IOCTL_GET_SECTOR_SIZE, &sector_size) == 0) &&
+			(sector_size == (uint16_t)sector_size)) {
+			*(uint16_t *)buff = (uint16_t)sector_size;
+		} else {
+			ret = RES_ERROR;
+		}
+		break;
+
+	case GET_BLOCK_SIZE:
+		if (disk_access_ioctl(pdrv_str[pdrv],
+				DISK_IOCTL_GET_ERASE_BLOCK_SZ, buff) != 0) {
+			ret = RES_ERROR;
+		}
+		break;
+
+	default:
+		ret = RES_PARERR;
+		break;
+	}
+	return ret;
+}