The eCos configuration store is a simple typed key/value store which uses NAND flash for its persistent storage.

The library is aimed at applications that wish to store simple configuration data without the overhead of a fully NAND-aware filesystem. It is also used by RedBoot to store persistent configuration data.

The following functionality is provided:

The main entry points to the config store logic are as follows:

/* From <cyg/configstore/write.h>.
 * These functions write out a key, overwriting it if it is already there.
 * They return 0 for success or a negative errno value; see the header
 * file for details.
 */
externC
int cyg_configstore_write_int(const char *key, cyg_uint32 i);
externC
int cyg_configstore_write_bool(const char *key, cyg_bool b);
externC
int cyg_configstore_write_bytes(const char *key, void *src, cyg_uint32 len);
externC
int cyg_configstore_write_string(const char *key, const char *data);

/* Erases a single key */
externC
int cyg_configstore_erase_keystr(const char *key);

/* From <cyg/configstore/read.h>.
 * These functions read out a key or header.
 * They return 0 for success or a negative errno value; see the header
 * file for details. */

externC
int cyg_configstore_read_int(const char *key, cyg_uint32 *i);
externC
int cyg_configstore_read_bool(const char *key, cyg_bool *b);

/* Note:
* For bytes and strings, check *len_io after read to see the actual number
* of bytes read, INCLUDING the trailing NUL. */
externC
int cyg_configstore_read_bytes(const char *key, CYG_BYTE *buf, unsigned *len_io);
externC
int cyg_configstore_read_string(const char *key, char *buf, unsigned *len_io);

/* Reading out only the header allows you to check a key's type and size. */
externC
int cyg_configstore_read_header(const char *key, cyg_configstore_header_t *hdr);

/* From <cyg/configstore/util.h>. */

/* Lists all keys in the store (to diag_printf).
 * Not really machine-readable; intended for human-read debugging. */
externC
void cyg_configstore_list(void);

/* Dumps out everything in the store (to diag_printf).
 * Intended for human-read debugging.
 * NOTE: This may emit large amounts of output, which may
 * take an excessive length of time over a slow debug channel. */
externC
void cyg_configstore_dump(void);

For more details of the types and structures used, refer to <cyg/configstore/serialise.h> and <cyg/configstore/record.h> .

	Note
	Both store keys, and strings in the store, should not contain the ASCII NUL (0x00) character. Behaviour in this case is undefined.

57.2.2. Configuration

If the NAND array reports an error when writing or erasing a block, the config store will automatically retry the operation, up to CYGNUM_CONFIG_STORE_RETRIES times. The default setting is 3 retries.

The config store is allocated a single NAND partition. The device and partition are configured by the CDL options CYGDAT_CONFIG_STORE_DEVICE and CYGNUM_CONFIG_STORE_PARTITION. Normally CYGDAT_CONFIG_STORE_DEVICE is set by the platform HAL; CYGNUM_CONFIG_STORE_PARTITION may also be hard-wired, if RedBoot or other boot loader needs it.

To configure partition sizes, refer to the eCos HAL documents for your platform. It is recommended to allow a reasonable number of blocks (5-10) for the config store, in order to allow for blocks wearing out over the lifetime of the device.

Caution

If the config store is to be shared between multiple clients - for example, RedBoot and an application - the partition geometry must be configured identically to both of them. Be aware that changing the geometry in CDL will not update RedBoot unless you also reconfigure, rebuild and reflash it! If other applications write other data to the NAND array, care should be taken to not overwrite the config store. It is recommended to give them their own partition.