<!-- {{{ Banner                         -->

<!-- =============================================================== -->
<!--                                                                 -->
<!--     flash.sgml                                                  -->
<!--                                                                 -->
<!--     eCos FLASH support                                          -->
<!--                                                                 -->
<!-- =============================================================== -->
<!-- ####COPYRIGHTBEGIN####                                          -->
<!--                                                                 -->
<!-- =============================================================== -->
<!-- Copyright (C) 2004 Andrew Lunn                                  -->
<!-- This material may be distributed only subject to the terms      -->
<!-- and conditions set forth in the Open Publication License, v1.0  -->
<!-- or later (the latest version is presently available at          -->
<!-- http://www.opencontent.org/openpub/)                            -->
<!-- Distribution of the work or derivative of the work in any       -->
<!-- standard (paper) book form is prohibited unless prior           -->
<!-- permission obtained from the copyright holder                   -->
<!-- =============================================================== -->
<!--                                                                 -->      
<!-- ####COPYRIGHTEND####                                            -->
<!-- =============================================================== -->
<!-- #####DESCRIPTIONBEGIN####                                       -->
<!--                                                                 -->
<!-- ####DESCRIPTIONEND####                                          -->
<!-- =============================================================== -->

<!-- }}} -->

<PART id="io-flash">
<TITLE>FLASH Library</TITLE>
<CHAPTER id="ecos-flash-library">
<TITLE>The eCos FLASH Library</TITLE>
<PARA>The FLASH library is an optional part of eCos, and is only
	applicable to some platforms.</PARA>
<PARA>The eCos FLASH library provides the following functionality:</PARA>

<orderedlist>
<listitem><PARA>Identifying installed device of a FLASH family.
          </PARA>
</listitem>
<listitem><PARA>Read, erasing and writing to FLASH blocks.</PARA></listitem>
<listitem><PARA>Validating an address is within the FLASH.</PARA></listitem>
<listitem><PARA>Determining the number and size of FLASH blocks.
          <PARA></listitem>
</orderedlist>

<PARA> There are two APIs with the flash library. The old API is
retained for backwards compatibility reasons, but should slowly be
replaced with the new API which is much more flexible and does not
pollute the name space as much.
</PARA>

<SECT1>
<TITLE>Notes on using the FLASH library</TITLE>

<PARA>FLASH devices cannot be read from when an erase or write
operation is active. This means it is not possible to execute code
from flash while an erase or write operation is active. It is possible
to use the library when the executable image is resident in FLASH. The
low level drivers are written such that the linker places the
functions that actually manipulate the flash into RAM.  However the
library may not be interrupt safe. An interrupt must not cause
execution of code that is resident in FLASH. This may be the image
itself, or RedBoot. In some configurations of eCos, ^C on the serial
port or debugging via Ethernet may cause an interrupt handler to call
RedBoot. If RedBoot is resident in FLASH this will cause a crash.
Similarly, if another thread invokes a virtual vector function to
access RedBoot, eg to perform a <FUNCTION>diag_printf()</FUNCTION> a
crash could result.
</PARA>

<PARA> Thus with a ROM based image or a ROM based Redboot it is
recommended to disable interrupts while erasing or programming
flash. Using both a ROMRAM or RAM images and a ROMRAM or RAM RedBoot
are safe and there is no need to disable interrupts. Similarly, 
</PARA>
</SECT1>

<SECT1>
<TITLE>Danger, Will Robinson! Danger!</TITLE>

<PARA>Unlike nearly every other aspect of embedded system programming,
getting it wrong with FLASH devices can render your target system
useless. Most targets have a boot loader in the FLASH. Without this
boot loader the target will obviously not boot. So before starting to
play with this library its worth investigating a few things. How do
you recover your target if you delete the boot loader? Do you have the
necessary JTAG cable? Or is specialist hardware needed? Is it even
possible to recover the target boards or must it be thrown into the
rubbish bin? How does killing the board affect your project schedule?
</PARA>

</SECT1>
</CHAPTER>

<CHAPTER id="ecos-flash-v2">
<TITLE>The Version 2 eCos FLASH API</TITLE>

<PARA> 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. </PARA>

<SECT1 id="ecos-flash-v2-api">
<TITLE>FLASH user API</TITLE>
<PARA> 

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

<SECT2>
<TITLE>Initializing the FLASH library</TITLE>

<PARA>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: </PARA>

<PROGRAMLISTING>__externC int cyg_flash_init(const cyg_flash_printf *pf); 
typedef int cyg_flash__printf(const char *fmt, ...); </PROGRAMLISTING>

<PARA>
The parameter <parameter>pf</parameter> is a pointer to a function
which is to be used for diagnostic output. Typically the function
<function>diag_printf()</function> will be passed. Normally this
function is not used by the higher layer of the library unless
<literal>CYGSEM_IO_FLASH_CHATTER</literal> is enabled.  Passing a
<parameter>NULL</parameter> is not recommended, even when
CYGSEM_IO_FLASH_CHATTER is disabled. The lower layers of the library
may unconditionally call this function, especially when errors occur,
probably resulting in a more serious error/crash!.</PARA>
</SECT2>

<SECT2>
<TITLE>Retrieving information about FLASH devices</TITLE> 

<PARA>
The following five functions return information about the FLASH.
</PARA>

<PROGRAMLISTING>
__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);
__externC int cyg_flash_code_overlaps(const flashaddr_t start, const flashaddr_t end);
__extern size_t cyg_flash_block_size(const cyg_flashaddr_t flash_base);

typedef struct cyg_block_info
    size_t                    block_size;
    cyg_unit32                blocks;
} cyg_block_info_t;

typedef struct {
    flashaddr_t               start;          // First address
    flashaddr_t               end;            // Last address
    cyg_uint32                num_block_infos // Number of entries
    cyg_block_info_t          *blocks_info;   // Info about one block size
} cyg_flash_info_t;
</PROGRAMLISTING>

<PARA><FUNCTION>cyg_flash_get_info()</FUNCTION> is the main function
to get information about installed flash devices.  Parameter
<PARAMETER>devno</PARAMETER> is used to iterate over the available
flash devices, starting from 0. If the devno'th device exists, the
structure pointed to by <PARAMETER>info</PARAMETER> is filled in and
<LITERAL>CYG_FLASH_ERR_OK</LITERAL> is returned, otherwise
<LITERAL>CYG_FLASH_ERR_INVALID</LITERAL>.
<FUNCTION>cyg_flash_get_info()</FUNCTION> if similar, but returns the
information about the flash device at the given address.
<FUNCTION>cyg_flash_block_size()</FUNCTION> returns the size of the
block at the given address.  <FUNCTION>cyg_flash_verify_addr()
</FUNCTION> tests if the target addresses is within one of the FLASH
devices, returning <LITERAL>CYG_FLASH_ERR_OK </LITERAL> if so.
<FUNCTION> cyg_flash_code_overlaps() </FUNCTION> checks if the
executing code is resident in the section of flash indicated by
<PARAMETER>start</PARAMETER> and <PARAMETER> end </PARAMETER>.  If
this function returns <LITERAL>CYG_FLASH_ERR_OK</LITERAL> the code is
inside the address refion given. Erase and program operations within
this range are very likely to cause the target to crash and burn
horribly. Note the FLASH library does allow you to shoot yourself in
the foot in this way.</PARA>
</SECT2>
 <SECT2>

<TITLE>Reading from FLASH</TITLE>

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

<PROGRAMLISTING>
__externC int cyg_flash_read(flashaddr_t *flash_base, const void *ram_base, const size_t len, flashaddr_t **err_address);
</PROGRAMLISTING>

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

<PARA>
The second method is to simply <FUNCTION>memcpy()</FUNCTION> 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.
</PARA>

</SECT2>
<SECT2>

<TITLE>Erasing areas of FLASH</TITLE>

<PARA>
Blocks of FLASH can be erased using the following function:
</PARA>

<PROGRAMLISTING>__externC int cyg_flash_erase(flashaddr_t *flash_base, const size_t len, flashaddr_t **err_address);
</PROGRAMLISTING>

<PARA>
<PARAMETER>flash_base</PARAMETER> is where in the flash to erase
from. <PARAMETER>len</PARAMETER> is the minimum number of bytes to
erase in the FLASH and <PARAMETER>err_address</PARAMETER> 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. <PARAMETER>flash_base</PARAMETER> may be anywhere
within the first block to be erased and <PARAMETER>flash_base+len
</PARAMETER> maybe anywhere in the last block to be erased.  </PARA>

</SECT2>
<SECT2>

<TITLE>Programming the FLASH</TITLE>

<PARA> Programming of the flash is achieved using the following
function.</PARA>

<PROGRAMLISTING>__externC int cyg_flash_program(const flashaddr_t *flash_base, void *ram_base, const size_t len, flashaddr_t **err_address);
</PROGRAMLISTING>

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

</SECT2>
<SECT2>

<TITLE>Locking and unlocking blocks</TITLE>

<PARA>
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 <LITERAL>
CYGHWR_IO_FLASH_BLOCK_LOCKING</LITERAL> is enabled then the following
two functions are available:</PARA>

<PROGRAMLISTING>
__externC int cyg_flash_lock(const flashaddr_t *flash_base, const size_t len, flashaddr_t **err_address);
__externC int cyg_flash_unlock(const flashaddr_t *flash_base, const size_t len, flashaddr_t **err_address);
</PROGRAMLISTING>

</SECT2>

<SECT2>
<TITLE>Locking FLASH Mutex's</TITLE>

<PARA>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.</PARA>

<PROGRAMLISTING>
__externC int cyg_flash_mutex_lock(const flashaddr_t *from, const size_t len);
__externC int cyg_flash_mutex_unlock(const flashaddr_t *from, const size_t len);
</PROGRAMLISTING>

<SECT2>

<TITLE>Return values and errors</TITLE>

<PARA>All the functions above, except <FUNCTION>cyg_flash_code_overlaps()
</FUNCTION> return one of the following return values.</PARA>

<PROGRAMLISTING>
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
</PROGRAMLISTING>

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

<PROGRAMLISTING>__externC const char *cyg_flash_errmsg(const int err);
</PROGRAMLISTING>
</SECT2>

<SECT1 id="ecos-flash-v2-dev">
<TITLE>FLASH device API</TITLE> <PARA>This section describes the API
between the FLASH IO library the FLASH device drivers.</PARA>

<SECT2>
<TITLE>The FLASH device Structure</TITLE>

<PARA>This structure keeps all the information about a single driver.</PARA>

<PROGRAMLISTING>struct cyg_flash_dev {
    struct cyg_flash_dev_funs *funs;           // Function pointers
    flashaddr_t               *start;          // First address
    flashaddr_t               *end;            // Last address
    void                      *priv;           // Devices private data
    cyg_uint32                num_block_infos; // Number of entries
    cyg_block_info_t          *blocks_info;    // Info about one block size


// The following are only written to by the FLASH IO layer.
    cyg_flash_printf          *pf;             // Pointer to diagnostic printf
    cyg_bool                  init;            // Device has been initialized
#ifdef CYG_KERNEL
    cyg_mutex_t               mutex;           // Mutex for thread safeness
#endif
    struct cyg_flash_dev      *next;           // Pointer to next device
}

struct cyg_flash_dev_funs {
    int (*flash_init) (struct cyg_flash_dev *dev);
    size_t (*flash_query) (struct cyg_flash_dev *dev, void * data, const size_t len);
    int (*flash_erase_block) (struct cyg_flash_dev *dev, const flashaddr_t *block_base);
    int (*flash_program) (struct cyg_flash_dev *dev, flashaddr_t *base, const void* data, const size_t len);
    int (*flash_read) (struct cyg_flash_dev *dev, const flashaddr_t *base, void* data, const size_t len);
    int (*flash_hwr_map_error) (struct cyg_flash_dev *dev, int err);
#ifdef CYGHWR_IO_FLASH_BLOCK_LOCKING
    int (*flash_block_lock) (struct cyg_flash_dev *dev, const flashaddr_t *block_base);
    int (*flash_block_unlock) (struct cyg_flash_dev *dev, const flashaddr_t *block_base);
#endif
}
</PROGRAMLISTING>

<PARA>The FLASH IO layer will only pass requests for operations on a single block.
</SECT1>
</CHAPTER>

<CHAPTER id="ecos-flash-v1">
<TITLE>The legacy Version 1 eCos FLASH API</TITLE>
<PARA>
The library has a number of limitations:</PARA>

<orderedlist>
<listitem><PARA>Only one family of FLASH device may be supported at once.
         </PARA>
</listitem>
<listitem><PARA>Multiple devices of one family are supported, but they must 
                be contiguous in memory.
          </PARA>
</listitem>
<listitem><PARA>The library is not thread or interrupt safe under 
                some conditions.
          </PARA>
</listitem>
<listitem><PARA>The library currently does not use the eCos naming 
                 convention for its functions. This may change in the
                 future but backward compatibility is likely to be kept.
          </PARA>
</listitem>
</orderedlist>

<PARA> 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. </PARA>

<SECT1 id="ecos-flash-v1-api">
<TITLE>FLASH user API</TITLE>

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


<SECT2>
<TITLE>Initializing the FLASH library</TITLE>

<PARA>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: </PARA>

<PROGRAMLISTING>externC int flash_init( _printf *pf ); 
typedef int _printf(const char *fmt, ...); </PROGRAMLISTING>

<PARA>
The parameter <parameter>pf</parameter> is a pointer to a function
which is to be used for diagnostic output. Typically the function
<function>diag_printf()</function> will be passed. Normally this
function is not used by the higher layer of the library unless
<literal>CYGSEM_IO_FLASH_CHATTER</literal> is enabled.  Passing a
<parameter>NULL</parameter> is not recommended, even when
CYGSEM_IO_FLASH_CHATTER is disabled. The lower layers of the library
may unconditionally call this function, especially when errors occur,
probably resulting in a more serious error/crash!.</PARA>
</SECT2>

<SECT2>
<TITLE>Retrieving information about the FLASH</TITLE> 

<PARA>
The following four functions return information about the FLASH.
</PARA>

<PROGRAMLISTING>externC int flash_get_block_info(int *block_size, int *blocks);
externC int flash_get_limits(void *target, void **start, void **end);
externC int flash_verify_addr(void *target);
externC bool flash_code_overlaps(void *start, void *end);
</PROGRAMLISTING>

<PARA>
The function <FUNCTION>flash_get_block_info()</FUNCTION> returns the
size and number of blocks. When the device has a mixture of block
sizes, the size of the "normal" block will be returned. Please read
the source code to determine exactly what this means.
<FUNCTION>flash_get_limits()</FUNCTION> returns the lower and upper
memory address the FLASH occupies. The <PARAMETER>target</PARAMETER>
parameter is current unused. <FUNCTION> flash_verify_addr()
</FUNCTION> tests if the target addresses is within the flash,
returning <LITERAL>FLASH_ERR_OK</LITERAL> if so. Lastly, <FUNCTION>
flash_code_overlaps() </FUNCTION> checks if the executing code is
resident in the section of flash indicated by
<PARAMETER>start</PARAMETER> and <PARAMETER> end</PARAMETER>. If this
function returns true, erase and program operations within this range
are very likely to cause the target to crash and burn horribly. Note
the FLASH library does allow you to shoot yourself in the foot in this
way.</PARA>

</SECT2>
<SECT2>

<TITLE>Reading from FLASH</TITLE>

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

<PROGRAMLISTING>
externC int flash_read(void *flash_base, void *ram_base, int len, void **err_address);
</PROGRAMLISTING>

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

<PARA>
The second method is to simply <FUNCTION>memcpy()</FUNCTION> 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.
</PARA>

</SECT2>
<SECT2>

<TITLE>Erasing areas of FLASH</TITLE>

<PARA>
Blocks of FLASH can be erased using the following function:
</PARA>

<PROGRAMLISTING>externC int flash_erase(void *flash_base, int len, void **err_address);
</PROGRAMLISTING>

<PARA>
<PARAMETER>flash_base</PARAMETER> is where in the flash to erase
from. <PARAMETER>len</PARAMETER> is the minimum number of bytes to
erase in the FLASH and <PARAMETER>err_address</PARAMETER> 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. <PARAMETER>flash_base</PARAMETER> may be anywhere
within the first block to be erased and <PARAMETER>flash_base+len
</PARAMETER> maybe anywhere in the last block to be erased.  </PARA>

</SECT2>
<SECT2>

<TITLE>Programming the FLASH</TITLE>

<PARA> Programming of the flash is achieved using the following
function.</PARA>

<PROGRAMLISTING>externC int flash_program(void *flash_base, void *ram_base, int len, void **err_address);
</PROGRAMLISTING>

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

</SECT2>
<SECT2>

<TITLE>Locking and unlocking blocks</TITLE>

<PARA>
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 <LITERAL>
CYGHWR_IO_FLASH_BLOCK_LOCKING</LITERAL> is enabled then the following
two functions are available:</PARA>

<PROGRAMLISTING>
externC int flash_lock(void *flash_base, int len, void **err_address);
externC int flash_unlock(void *flash_base, int len, void **err_address);
</PROGRAMLISTING>

</SECT2>
<SECT2>

<TITLE>Return values and errors</TITLE>

<PARA>All the functions above, except <FUNCTION>flash_code_overlaps()
</FUNCTION> return one of the following return values.</PARA>

<PROGRAMLISTING>
FLASH_ERR_OK              No error - operation complete
FLASH_ERR_INVALID         Invalid FLASH address
FLASH_ERR_ERASE           Error trying to erase
FLASH_ERR_LOCK            Error trying to lock/unlock
FLASH_ERR_PROGRAM         Error trying to program
FLASH_ERR_PROTOCOL        Generic error
FLASH_ERR_PROTECT         Device/region is write-protected
FLASH_ERR_NOT_INIT        FLASH info not yet initialized
FLASH_ERR_HWR             Hardware (configuration?) problem
FLASH_ERR_ERASE_SUSPEND   Device is in erase suspend mode
FLASH_ERR_PROGRAM_SUSPEND Device is in program suspend mode
FLASH_ERR_DRV_VERIFY      Driver failed to verify data
FLASH_ERR_DRV_TIMEOUT     Driver timed out waiting for device
FLASH_ERR_DRV_WRONG_PART  Driver does not support device
FLASH_ERR_LOW_VOLTAGE     Not enough juice to complete job
</PROGRAMLISTING>

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

<PROGRAMLISTING>externC char *flash_errmsg(int err);
</PROGRAMLISTING>
</SECT2>

<SECT2>

<TITLE> Notes on using the FLASH library</TITLE>

<PARA>
The FLASH library evolved from the needs and environment of RedBoot
rather than being a general purpose eCos component. This history
explains some of the problems with the library.  </PARA>

<PARA>The library is not thread safe. Multiple simultaneous calls to
its library functions will likely fail and may cause a crash. It is
the callers responsibility to use the necessary mutex's if needed.
<PARA>

</SECT2>
</SECT1>

<SECT1 id="ecos-flash-v1-dev">
<TITLE>FLASH device API</TITLE> <PARA>This section describes the API
between the FLASH IO library the FLASH device drivers.</PARA>

<SECT2>
<TITLE>The flash_info structure</TITLE>

<PARA> The <parameter>flash_info</parameter>structure is used by both
the FLASH IO library and the device driver.</PARA>
<PROGRAMLISTING>struct flash_info {
    int   block_size;   // Assuming fixed size "blocks"
    int   blocks;       // Number of blocks
    int   buffer_size;  // Size of write buffer (only defined for some devices)
    unsigned long block_mask;
    void *start, *end;  // Address range
    int   init;         // FLASH API initialised
    _printf *pf;        // printf like function for diagnostics
};
</PROGRAMLISTING>

<PARA>block_mask is used internally in the FLASH IO library. It
contains a mask which can be used to turn an arbitrary address in
flash to the base address of the block which contains the
address.</PARA>

<PARA>There exists one global instance of this structure with the name
<parameter>flash_info</parameter>. All calls into the device driver
makes use of this global structure to maintain state.</PARA>

</SECT2>

<SECT2>
<TITLE>Initializing the device driver</TITLE>

<PARA>The FLASH IO library will call the following function to
initialize the device driver:</PARA>

<PROGRAMLISTING>externC int  flash_hwr_init(void);
</PROGRAMLISTING>

<PARA>The device driver should probe the hardware to see if the FLASH
devices exist. If it does it should fill in <parameter>start, end,
blocks and block_size.</parameter>If the FLASH contains a write buffer
the size of this should be placed in <parameter>buffer_size
</parameter>. On successful probing the function should return
<literal>FLASH_ERR_OK</literal>. When things go wrong it can be
assumed that <parameter>pf</parameter> points to a printf like
function for outputting error messages.
</PARA>
</SECT2>

<SECT2>
<TITLE>Querying the FLASH</TITLE>

<PARA>FLASH devices can be queried to return there manufacture ID,
size etc. This function allows this information to be returned.</PARA>

<PROGRAMLISTING>int flash_query(unsigned char *data);</PROGRAMLISTING>

<PARA>The caller must know the size of data to be returned and provide
an appropriately sized buffer pointed to be parameter
<parameter>data</parameter>. This function is generally used by
<function>flash_hwr_init()</function>.</PARA>

</SECT2>
<SECT2>
<TITLE>Erasing a block of FLASH</TITLE>

<PARA>So that the FLASH IO layer can erase a block of FLASH the
following function should be provided.</PARA>

<PROGRAMLISTING>int flash_erase_block(volatile flash_t *block, unsigned int block_size);
</PROGRAMLISTING>

</SECT2>
<SECT2>
<TITLE>Programming a region of FLASH</TITLE>

<PARA>The following function must be provided so that data can be
written into the FLASH.</PARA>

<PROGRAMLISTING>int flash_program_buf(volatile flash_t *addr, flash_t *data, int len,
                  unsigned long block_mask, int buffer_size);</PROGRAMLISTING>

<PARA>The device will only be asked to program data in one block of
the flash. The FLASH IO layer will break longer user requests into a
smaller writes.</PARA>

<SECT2>
<TITLE>Reading a region from FLASH</TITLE>

<PARA>Some FLASH devices are not memory mapped so it is not possible
to read there contents directly. The following function read a region
of FLASH.</PARA>

<PROGRAMLISTING>int flash_read_buf(volatile flash_t* addr, flash_t* data, int len);
</PROGRAMLISTING>

<PARA>As with writing to the flash, the FLASH IO layer will break
longer user requests for data into a number of reads which are at
maximum one block in size.</PARA>

<PARA>A device which cannot be read directy should set
<LITERAL>CYGSEM_IO_FLASH_READ_INDIRECT</LITERAL> so that the IO layer
makes use of the <function>flash_read_buf()</function>function.

</SECT2> 

<SECT2>
<TITLE>Locking and unlocking FLASH blocks</TITLE>

<PARA>Some flash devices allow blocks to be locked so that they cannot
be written to. The device driver should provide the following
functions to manipulate these locks.</PARA>

<PROGRAMLISTING>int flash_lock_block(volatile flash_t *block);
int flash_unlock_block(volatile flash_t *block, int block_size, int blocks);
</PROGRAMLISTING>

<PARA>These functions are only used if
<LITERAL>CYGHWR_IO_FLASH_BLOCK_LOCKING</LITERAL></PARA>

</SECT2>

<SECT2>
<TITLE>Mapping FLASH error codes to FLASH IO error codes</TITLE>

<PARA>The functions <function>flash_erase_block(),
flash_program_buf(), flash_read_buf(), flash_lock_block() and
flash_unlock_block()</function> return an error code which is specific
to the flash device. To map this into a FLASH IO error code, the
driver should provide the following function: </PARA>

<PROGRAMLISTING>int flash_hwr_map_error(int err);</PROGRAMLISTING>

</SECT2>

<SECT2>
<TITLE>Determining if code is in FLASH</TITLE>

<PARA>Although a general function, the device driver is expected to
provide the implementation of the function
<function>flash_code_overlaps()</function>.</PARA>

</SECT2>

<SECT2>
<TITLE>Implementation Notes</TITLE>

<PARA>The FLASH IO layer will manipulate the caches as required. The
device drivers do not need to enable/disable caches when performing
operations of the FLASH.<PARA>

<PARA>Device drivers should keep all chatter to a minimum when
<literal>CYGSEM_IO_FLASH_CHATTER</literal> is not defined. All output
should use the print function in the <parameter>pf</parameter> in
<parameter>flash_info</parameter> and not
<function>diag_printf()</function></PARA>

<PARA>Device driver functions which manipulate the state of the flash
so that it cannot be read from for program execute need to ensure
there code is placed into RAM. The linker will do this if the
appropriate attribute is added to the function. e.g:</PARA>

<PROGRAMLISTING>int flash_program_buf(volatile flash_t *addr, flash_t *data, int len,
                  unsigned long block_mask, int buffer_size)
 __attribute__ ((section (".2ram.flash_program_buf")));</PROGRAMLISTING>

</SECT2>
</SECT1>
</CHAPTER> 
</PART>
