Chapter 60. The Version 2 eCos FLASH API

There are two APIs described here. The first is the application API which programs should use. The second API is that between the FLASH IO library and the device drivers.


All of the functions described below are declared in the header file <cyg/io/flash.h> which all users of the FLASH library should include.

Initializing the FLASH library

The FLASH library needs to be initialized before other FLASH operations can be performed. This only needs to be done once. The following function will only do the initialization once so it's safe to call multiple times:

__externC int cyg_flash_init(cyg_flash_printf *pf); 

The parameter pf must always be set to NULL. It exists solely for backward compatibility and other settings are deprecated and obsolete. Past use of this parameter has now been replaced with use of the cyg_flash_set_global_printf function.

Retrieving information about FLASH devices

The following five functions return information about the FLASH.

__externC int cyg_flash_get_info(cyg_uint32 devno, cyg_flash_info_t * info);
__externC int cyg_flash_get_info_addr(cyg_flashaddr_t flash_base, cyg_flash_info_t * info);
__externC int cyg_flash_verify_addr(const flashaddr_t address);
__extern size_t cyg_flash_block_size(const cyg_flashaddr_t flash_base);

typedef struct cyg_flash_block_info
    size_t                    block_size;
    cyg_uint32                blocks;
} cyg_flash_block_info_t;

typedef struct {
    cyg_flashaddr_t              start;          // First address
    cyg_flashaddr_t              end;            // Last address
    cyg_uint32                   num_block_infos;// Number of entries
    const cyg_flash_block_info_t *block_info;    // Info about one block size
} cyg_flash_info_t;

cyg_flash_get_info() is the main function to get information about installed flash devices. Parameter devno is used to iterate over the available flash devices, starting from 0. If the devno'th device exists, the structure pointed to by info is filled in and CYG_FLASH_ERR_OK is returned, otherwise CYG_FLASH_ERR_INVALID. cyg_flash_get_info_addr() is similar, but returns the information about the flash device at the given address. cyg_flash_block_size() returns the size of the block at the given address. cyg_flash_verify_addr() tests if the target addresses is within one of the FLASH devices, returning CYG_FLASH_ERR_OK if so.

Reading from FLASH

There are two methods for reading from FLASH. The first is to use the following function.

__externC int cyg_flash_read(cyg_flashaddr_t flash_base, void *ram_base, size_t len, cyg_flashaddr_t *err_address);

flash_base is where in the flash to read from. ram_base indicates where the data read from flash should be placed into RAM. len is the number of bytes to be read from the FLASH and err_address is used to return the location in FLASH that any error occurred while reading.

The second method is to simply memcpy() directly from the FLASH. This is not recommended since some types of device cannot be read in this way, eg NAND FLASH. Using the FLASH library function to read the FLASH will always work so making it easy to port code from one FLASH device to another.

Erasing areas of FLASH

Blocks of FLASH can be erased using the following function:

__externC int cyg_flash_erase(cyg_flashaddr_t flash_base, size_t len, cyg_flashaddr_t *err_address);

flash_base is where in the flash to erase from. len is the minimum number of bytes to erase in the FLASH and err_address is used to return the location in FLASH that any error occurred while erasing. It should be noted that FLASH devices are block oriented when erasing. It is not possible to erase a few bytes within a block, the whole block will be erased. flash_base may be anywhere within the first block to be erased and flash_base+len may be anywhere in the last block to be erased.

Programming the FLASH

Programming of the flash is achieved using the following function.

__externC int cyg_flash_program(cyg_flashaddr_t flash_base, void *ram_base, size_t len, cyg_flashaddr_t *err_address);

flash_base is where in the flash to program from. ram_base indicates where the data to be programmed into FLASH should be read from in RAM. len is the number of bytes to be program into the FLASH and err_address is used to return the location in FLASH that any error occurred while programming.

Locking and unlocking blocks

Some flash devices have the ability to lock and unlock blocks. A locked block cannot be erased or programmed without it first being unlocked. For devices which support this feature and when CYGHWR_IO_FLASH_BLOCK_LOCKING is enabled then the following two functions are available:

__externC int cyg_flash_lock(const cyg_flashaddr_t flash_base, size_t len, cyg_flashaddr_t *err_address);
__externC int cyg_flash_unlock(const cyg_flashaddr_t flash_base, size_t len, cyg_flashaddr_t *err_address);

For some devices the granularity will be at the whole device level, where the code will lock or unlock all of the blocks at the same time.

Locking FLASH mutexes

When the eCos kernel package is included in the eCos configuration, the FLASH IO library will perform mutex locking on FLASH operations. This makes the API defined here thread safe. However applications may wish to directly access the contents of the FLASH. In order for this to be thread safe it is necessary for the application to use the following two functions to inform the FLASH IO library that the FLASH devices are being used and other API calls should be blocked.

__externC int cyg_flash_mutex_lock(const cyg_flashaddr_t from, size_t len);
__externC int cyg_flash_mutex_unlock(const cyg_flashaddr_t from, size_t len);

Configuring diagnostic output

Each FLASH device can have an associated function which is called to perform diagnostic output. The function to be used can be configured with the following functions:

__externC int cyg_flash_set_printf(const cyg_flashaddr_t flash_base,
                                   cyg_flash_printf *pf);
__externC void cyg_flash_set_global_printf(cyg_flash_printf *pf);
typedef int cyg_flash_printf(const char *fmt, ...); 

The parameter pf is a pointer to a function which is to be used for diagnostic output. Typically the function diag_printf() will be passed. Normally this function is not used by the higher layer of the library unless CYGSEM_IO_FLASH_CHATTER is enabled. Passing a NULL causes diagnostic output from lower level drivers to be discarded.

cyg_flash_set_printf is used to set a diagnostic output function which will be used specifically when diagnostic output is attempted from the FLASH device driver associated with the base address of flash_base. An error will be returned if no FLASH device is found for this address, or the FLASH subsystem has not yet been initialised with cyg_flash_init.

cyg_flash_set_global_printf sets a diagnostic output function for all available FLASH devices. Any previous setting of a diagnostic output function (including with cyg_flash_set_printf) will be discarded. This function may be called prior to cyg_flash_init.

Return values and errors

All the functions above return one of the following return values.

CYG_FLASH_ERR_OK              No error - operation complete
CYG_FLASH_ERR_INVALID         Invalid FLASH address
CYG_FLASH_ERR_ERASE           Error trying to erase
CYG_FLASH_ERR_LOCK            Error trying to lock/unlock
CYG_FLASH_ERR_PROGRAM         Error trying to program
CYG_FLASH_ERR_PROTOCOL        Generic error
CYG_FLASH_ERR_PROTECT         Device/region is write-protected
CYG_FLASH_ERR_NOT_INIT        FLASH info not yet initialized
CYG_FLASH_ERR_HWR             Hardware (configuration?) problem
CYG_FLASH_ERR_ERASE_SUSPEND   Device is in erase suspend mode
CYG_FLASH_ERR_PROGRAM_SUSPEND Device is in program suspend mode
CYG_FLASH_ERR_DRV_VERIFY      Driver failed to verify data
CYG_FLASH_ERR_DRV_TIMEOUT     Driver timed out waiting for device
CYG_FLASH_ERR_DRV_WRONG_PART  Driver does not support device
CYG_FLASH_ERR_LOW_VOLTAGE     Not enough juice to complete job

To turn an error code into a human readable string the following function can be used:

__externC const char *cyg_flash_errmsg(const int err);
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