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>Chapter 29. FLASH I/O devices</TD
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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="ECOS-FLASH-IODEVICE-USAGE"
>Using FLASH I/O devices</A
></H1
><P
>The FLASH I/O block devices can be accessed, read and written using
the standard interface supplied by the generic I/O
(<CODE
CLASS="VARNAME"
>CYGPKG_IO</CODE
>) package. These include the functions:
<CODE
CLASS="FUNCTION"
>cyg_io_lookup()</CODE
> to access the device and get a
handle, <CODE
CLASS="FUNCTION"
>cyg_io_read()</CODE
> and
<CODE
CLASS="FUNCTION"
>cyg_io_write()</CODE
> for sequential read and write
operations, <CODE
CLASS="FUNCTION"
>cyg_io_bread()</CODE
> and
<CODE
CLASS="FUNCTION"
>cyg_io_bwrite()</CODE
> for random access read and write
operations, and <CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
> and
<CODE
CLASS="FUNCTION"
>cyg_io_setconfig()</CODE
> for run-time configuration
inspection and control.</P
><P
>However there are two aspects that differ from some other I/O devices
accessed this way:</P
><P
></P
><OL
TYPE="1"
><LI
><P
>The first is that the lookup operation uses up
resources which must be subsequently freed when the last user of the
I/O handle is finished. The number of FLASH I/O devices that may be
simultaneously opened is configured with the
<CODE
CLASS="VARNAME"
>CYGNUM_IO_FLASH_BLOCK_DEVICES</CODE
> CDL option. After the
last user is finished, the device may be closed using
<CODE
CLASS="FUNCTION"
>cyg_io_setconfig()</CODE
> with the
<CODE
CLASS="VARNAME"
>CYG_IO_SET_CONFIG_CLOSE</CODE
> key. Reference counting to
ensure that it is only the last user that causes a close, is left to
higher layers.</P
></LI
><LI
><P
>The second is that write operations assume that the
flash is already erased. Attempting to write to Flash that has
already been written to may result in errors. Instead FLASH must
be erased before it may be written.</P
></LI
></OL
><P
>FLASH block devices can also be read and written using the
standard POSIX primitives, <CODE
CLASS="FUNCTION"
>open()</CODE
>,
<CODE
CLASS="FUNCTION"
>close()</CODE
>, <CODE
CLASS="FUNCTION"
>read()</CODE
>,
<CODE
CLASS="FUNCTION"
>write()</CODE
>, <CODE
CLASS="FUNCTION"
>lseek()</CODE
>, and so on
if the POSIX file I/O package (<CODE
CLASS="VARNAME"
>CYGPKG_FILEIO</CODE
>) is
included in the configuration. As with the eCos generic I/O interface
you must call <CODE
CLASS="FUNCTION"
>close()</CODE
> to ensure resources
are freed when the device is no longer used.</P
><P
>Other configuration keys are provided to perform FLASH erase
operations, and to retrieve device sizes, and FLASH block sizes at
a particular address. These operations are accessed with
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
> (or if using the POSIX
file I/O API, <CODE
CLASS="FUNCTION"
>cyg_fs_getinfo()</CODE
>) with the
following keys:</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><CODE
CLASS="VARNAME"
>CYG_IO_GET_CONFIG_FLASH_ERASE</CODE
></DT
><DD
><P
>This erases a region of FLASH.
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
> must be passed a
structure defined as per the following, which is also supplied
in <TT
CLASS="FILENAME"
><cyg/io/flash.h></TT
>:
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
CYG_ADDRESS offset;
size_t len;
int flasherr;
cyg_flashaddr_t err_address;
} cyg_io_flash_getconfig_erase_t;</PRE
></TD
></TR
></TABLE
></P
><P
> In this structure, <CODE
CLASS="STRUCTFIELD"
>offset</CODE
> specifies
the offset within the block device to erase, <CODE
CLASS="STRUCTFIELD"
>len</CODE
>
specifies the amount to address, <CODE
CLASS="STRUCTFIELD"
>flasherr</CODE
> is
set on return to specify an error with the FLASH erase operation itself,
and <CODE
CLASS="STRUCTFIELD"
>err_address</CODE
> is used if there was an error
to specify at which address the error happened.</P
></DD
><DT
><CODE
CLASS="VARNAME"
>CYG_IO_GET_CONFIG_FLASH_LOCK</CODE
></DT
><DD
><P
>This protects a region of FLASH using the locking facilities
available on the card, if provided by the underlying driver.
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
> must be passed a
structure defined as per the following:
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
CYG_ADDRESS offset;
size_t len;
int flasherr;
cyg_flashaddr_t err_address;
} cyg_io_flash_getconfig_lock_t;</PRE
></TD
></TR
></TABLE
></P
><P
> In this structure, <CODE
CLASS="STRUCTFIELD"
>offset</CODE
> specifies
the offset within the block device to lock, <CODE
CLASS="STRUCTFIELD"
>len</CODE
>
specifies the amount to address, <CODE
CLASS="STRUCTFIELD"
>flasherr</CODE
> is
set on return to specify an error with the FLASH lock operation itself,
and <CODE
CLASS="STRUCTFIELD"
>err_address</CODE
> is used if there was an error
to specify at which address the error happened. If locking
support is not available -EINVAL will be returned from
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
>.</P
></DD
><DT
><CODE
CLASS="VARNAME"
>CYG_IO_GET_CONFIG_FLASH_UNLOCK</CODE
></DT
><DD
><P
>This disables protection for a region of FLASH using the
unlocking facilities available on the card, if provided by the underlying driver.
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
> must be passed a
structure defined as per the following:
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
CYG_ADDRESS offset;
size_t len;
int flasherr;
cyg_flashaddr_t err_address;
} cyg_io_flash_getconfig_unlock_t;</PRE
></TD
></TR
></TABLE
></P
><P
> In this structure, <CODE
CLASS="STRUCTFIELD"
>offset</CODE
> specifies
the offset within the block device to unlock, <CODE
CLASS="STRUCTFIELD"
>len</CODE
>
specifies the amount to address, <CODE
CLASS="STRUCTFIELD"
>flasherr</CODE
> is
set on return to specify an error with the FLASH unlock operation itself,
and <CODE
CLASS="STRUCTFIELD"
>err_address</CODE
> is used if there was an error
to specify at which address the error happened. If unlocking
support is not available -EINVAL will be returned from
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
>.</P
></DD
><DT
><CODE
CLASS="VARNAME"
>CYG_IO_GET_CONFIG_FLASH_DEVSIZE</CODE
></DT
><DD
><P
>This returns the size of the FLASH block device. The
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
> function must be passed a
structure defined as per the following, which is also supplied
in <TT
CLASS="FILENAME"
><cyg/io/flash.h></TT
>:
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
size_t dev_size;
} cyg_io_flash_getconfig_devsize_t;</PRE
></TD
></TR
></TABLE
></P
><P
> In this structure, <CODE
CLASS="STRUCTFIELD"
>dev_size</CODE
> is used to
return the size of the FLASH device.</P
></DD
><DT
><CODE
CLASS="VARNAME"
>CYG_IO_GET_CONFIG_FLASH_DEVADDR</CODE
></DT
><DD
><P
>This returns the address in the virtual memory map that the
generic flash layer has been informed that this FLASH device is mapped to. Note
that some flash devices such as dataflash are not truly memory mapped,
and so this function only returns useful information when used with a true
memory mapped FLASH device. The
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
> function must be passed a
structure defined as per the following, which is also supplied
in <TT
CLASS="FILENAME"
><cyg/io/flash.h></TT
>:
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
cyg_flashaddr_t dev_addr;
} cyg_io_flash_getconfig_devaddr_t;</PRE
></TD
></TR
></TABLE
></P
><P
> In this structure, <CODE
CLASS="STRUCTFIELD"
>dev_addr</CODE
> is used to
return the address corresponding to the base of the FLASH device in the
virtual memory map.</P
></DD
><DT
><CODE
CLASS="VARNAME"
>CYG_IO_GET_CONFIG_FLASH_BLOCKSIZE</CODE
></DT
><DD
><P
>This returns the size of a FLASH block at a
supplied offset in the FLASH block device. The
<CODE
CLASS="FUNCTION"
>cyg_io_get_config()</CODE
> function must be passed a
structure defined as per the following, which is also supplied
in <TT
CLASS="FILENAME"
><cyg/io/flash.h></TT
>:
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>typedef struct {
CYG_ADDRESS offset;
size_t block_size;
} cyg_io_flash_getconfig_blocksize_t;</PRE
></TD
></TR
></TABLE
></P
><P
> In this structure, <CODE
CLASS="STRUCTFIELD"
>offset</CODE
> specifies the
address within the block device of which the FLASH block size is
required - a single FLASH device may contain blocks of differing
sizes. The <CODE
CLASS="STRUCTFIELD"
>block_size</CODE
> field is used to
return the block size at the specified offset.</P
></DD
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