磨损均衡 API¶
概述¶
ESP32 所使用的 flash,特别是 SPI flash 多数具备扇区结构,且每个扇区仅允许有限次数的擦除/修改操作。为了避免过度使用某一扇区,乐鑫提供了磨损均衡组件,无需用户介入即可帮助用户均衡各个扇区之间的磨损。
磨损均衡组件包含了通过分区组件对外部 SPI flash 进行数据读取、写入、擦除和存储器映射相关的 API 函数。磨损均衡组件还具有软件上更高级别的 API 函数,与 FAT 文件系统 协同工作。
磨损均衡组件与 FAT 文件系统组件共用 FAT 文件系统的扇区,扇区大小为 4096 字节,是标准 flash 扇区的大小。在这种模式下,磨损均衡组件性能达到最佳,但需要在 RAM 中占用更多内存。
为了节省内存,磨损均衡组件还提供了另外两种模式,均使用 512 字节大小的扇区:
性能模式:先将数据保存在 RAM 中,擦除扇区,然后将数据存储回 flash。如果设备在扇区擦写过程中突然断电,则整个扇区(4096 字节)数据将全部丢失。
安全模式:数据先保存在 flash 中空余扇区,擦除扇区后,数据即存储回去。如果设备断电,上电后可立即恢复数据。
设备默认设置如下:
定义扇区大小为 512 字节
默认使用性能模式
您可以使用配置菜单更改设置。
磨损均衡组件不会将数据缓存在 RAM 中。写入和擦除函数直接修改 flash,函数返回后,flash 即完成修改。
磨损均衡访问 API¶
处理 flash 数据常用的 API 如下所示:
wl_mount
- 为指定分区挂载并初始化磨损均衡模块wl_unmount
- 卸载分区并释放磨损均衡模块wl_erase_range
- 擦除 flash 中指定的地址范围wl_write
- 将数据写入分区wl_read
- 从分区读取数据wl_size
- 返回可用内存的大小(以字节为单位)wl_sector_size
- 返回一个扇区的大小
请尽量避免直接使用原始磨损均衡函数,建议您使用文件系统特定的函数。
内存大小¶
内存大小是根据分区参数在磨损均衡模块中计算所得,由于模块使用 flash 部分扇区存储内部数据,因此计算所得内存大小有少许偏差。
应用示例¶
storage/wear_levelling 中提供了一款磨损均衡驱动与 FatFs 库结合使用的示例。该示例初始化磨损均衡驱动,挂载 FAT 文件系统分区,并使用 POSIX(可移植操作系统接口)和 C 库 API 从中写入和读取数据。如需了解更多信息,请参考 storage/wear_levelling/README.md。
高级 API 参考¶
函数¶
-
esp_err_t
esp_vfs_fat_spiflash_mount
(const char *base_path, const char *partition_label, const esp_vfs_fat_mount_config_t *mount_config, wl_handle_t *wl_handle)¶ Convenience function to initialize FAT filesystem in SPI flash and register it in VFS.
This is an all-in-one function which does the following:
finds the partition with defined partition_label. Partition label should be configured in the partition table.
initializes flash wear levelling library on top of the given partition
mounts FAT partition using FATFS library on top of flash wear levelling library
registers FATFS library with VFS, with prefix given by base_prefix variable
This function is intended to make example code more compact.
- Return
ESP_OK on success
ESP_ERR_NOT_FOUND if the partition table does not contain FATFS partition with given label
ESP_ERR_INVALID_STATE if esp_vfs_fat_spiflash_mount was already called
ESP_ERR_NO_MEM if memory can not be allocated
ESP_FAIL if partition can not be mounted
other error codes from wear levelling library, SPI flash driver, or FATFS drivers
- Parameters
base_path
: path where FATFS partition should be mounted (e.g. “/spiflash”)partition_label
: label of the partition which should be usedmount_config
: pointer to structure with extra parameters for mounting FATFS[out] wl_handle
: wear levelling driver handle
-
struct
esp_vfs_fat_mount_config_t
Configuration arguments for esp_vfs_fat_sdmmc_mount and esp_vfs_fat_spiflash_mount functions.
Public Members
-
bool
format_if_mount_failed
If FAT partition can not be mounted, and this parameter is true, create partition table and format the filesystem.
-
int
max_files
Max number of open files.
-
size_t
allocation_unit_size
If format_if_mount_failed is set, and mount fails, format the card with given allocation unit size. Must be a power of 2, between sector size and 128 * sector size. For SD cards, sector size is always 512 bytes. For wear_levelling, sector size is determined by CONFIG_WL_SECTOR_SIZE option.
Using larger allocation unit size will result in higher read/write performance and higher overhead when storing small files.
Setting this field to 0 will result in allocation unit set to the sector size.
-
bool
-
esp_err_t
esp_vfs_fat_spiflash_unmount
(const char *base_path, wl_handle_t wl_handle)¶ Unmount FAT filesystem and release resources acquired using esp_vfs_fat_spiflash_mount.
- Return
ESP_OK on success
ESP_ERR_INVALID_STATE if esp_vfs_fat_spiflash_mount hasn’t been called
- Parameters
base_path
: path where partition should be registered (e.g. “/spiflash”)wl_handle
: wear levelling driver handle returned by esp_vfs_fat_spiflash_mount
中层 API 参考¶
Header File¶
Functions¶
-
esp_err_t
wl_mount
(const esp_partition_t *partition, wl_handle_t *out_handle)¶ Mount WL for defined partition.
- Return
ESP_OK, if the allocation was successfully;
ESP_ERR_INVALID_ARG, if WL allocation was unsuccessful;
ESP_ERR_NO_MEM, if there was no memory to allocate WL components;
- Parameters
partition
: that will be used for accessout_handle
: handle of the WL instance
-
esp_err_t
wl_unmount
(wl_handle_t handle)¶ Unmount WL for defined partition.
- Return
ESP_OK, if the operation completed successfully;
or one of error codes from lower-level flash driver.
- Parameters
handle
: WL partition handle
-
esp_err_t
wl_erase_range
(wl_handle_t handle, size_t start_addr, size_t size)¶ Erase part of the WL storage.
- Return
ESP_OK, if the range was erased successfully;
ESP_ERR_INVALID_ARG, if iterator or dst are NULL;
ESP_ERR_INVALID_SIZE, if erase would go out of bounds of the partition;
or one of error codes from lower-level flash driver.
- Parameters
handle
: WL handle that are related to the partitionstart_addr
: Address where erase operation should start. Must be aligned to the result of function wl_sector_size(…).size
: Size of the range which should be erased, in bytes. Must be divisible by result of function wl_sector_size(…)..
-
esp_err_t
wl_write
(wl_handle_t handle, size_t dest_addr, const void *src, size_t size)¶ Write data to the WL storage.
Before writing data to flash, corresponding region of flash needs to be erased. This can be done using wl_erase_range function.
- Note
Prior to writing to WL storage, make sure it has been erased with wl_erase_range call.
- Return
ESP_OK, if data was written successfully;
ESP_ERR_INVALID_ARG, if dst_offset exceeds partition size;
ESP_ERR_INVALID_SIZE, if write would go out of bounds of the partition;
or one of error codes from lower-level flash driver.
- Parameters
handle
: WL handle that are related to the partitiondest_addr
: Address where the data should be written, relative to the beginning of the partition.src
: Pointer to the source buffer. Pointer must be non-NULL and buffer must be at least ‘size’ bytes long.size
: Size of data to be written, in bytes.
-
esp_err_t
wl_read
(wl_handle_t handle, size_t src_addr, void *dest, size_t size)¶ Read data from the WL storage.
- Return
ESP_OK, if data was read successfully;
ESP_ERR_INVALID_ARG, if src_offset exceeds partition size;
ESP_ERR_INVALID_SIZE, if read would go out of bounds of the partition;
or one of error codes from lower-level flash driver.
- Parameters
handle
: WL module instance that was initialized beforedest
: Pointer to the buffer where data should be stored. Pointer must be non-NULL and buffer must be at least ‘size’ bytes long.src_addr
: Address of the data to be read, relative to the beginning of the partition.size
: Size of data to be read, in bytes.
-
size_t
wl_size
(wl_handle_t handle)¶ Get size of the WL storage.
- Return
usable size, in bytes
- Parameters
handle
: WL module handle that was initialized before
-
size_t
wl_sector_size
(wl_handle_t handle)¶ Get sector size of the WL instance.
- Return
sector size, in bytes
- Parameters
handle
: WL module handle that was initialized before