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FatFs R0.14b, released April 17, 2021

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Christopher Williams
2021-04-20 17:26:13 -07:00
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@@ -67,16 +67,16 @@ The FatFs module is a middleware written in ANSI C (C89). There is no platform d
<p><img src="../res/funcs.png" width="750" height="420" alt="functional diagram"></p>
<h4>Required Functions</h4>
<p>You need to provide only MAI functions required by FatFs module and nothing else. If any working device control module for the target system is available, you need to write only glue functions to attach it to the FatFs module. If not, you need to port another device control module or write it from scratch. Most of MAI functions are not that always required. For instance, any write function is not required in read-only configuration. Following table shows which function is required depends on the configuration options.</p>
<p>You need to provide only MAI functions required by FatFs module and nothing else. If a working device control module for the target system is available, you need to write only glue functions to attach it to the FatFs module. If not, you need to port another device control module or write it from scratch. Most of MAI functions are not that always required. For instance, the write function is not required in read-only configuration. Following table shows which function is required depends on the configuration options.</p>
<table class="lst2">
<tr><th>Function</th><th>Required when</th><th>Note</th></tr>
<tr><th>Function</th><th>Required when:</th><th>Note</th></tr>
<tr><td>disk_status<br>disk_initialize<br>disk_read</td><td>Always</td><td rowspan="5">Disk I/O functions.<br>Samples available in ffsample.zip.<br>There are many implementations on the web.</td></tr>
<tr><td>disk_write<br>get_fattime<br>disk_ioctl (CTRL_SYNC)</td><td>FF_FS_READONLY == 0</td></tr>
<tr><td>disk_ioctl (GET_SECTOR_COUNT)<br>disk_ioctl (GET_BLOCK_SIZE)</td><td>FF_USE_MKFS == 1</td></tr>
<tr><td>disk_ioctl (GET_SECTOR_SIZE)</td><td>FF_MAX_SS != FF_MIN_SS</td></tr>
<tr><td>disk_ioctl (CTRL_TRIM)</td><td>FF_USE_TRIM == 1</td></tr>
<tr><td>ff_uni2oem<br>ff_oem2uni<br>ff_wtoupper</td><td>FF_USE_LFN != 0</td><td>Unicode support functions.<br>Add optional module ffunicode.c to the project.</td></tr>
<tr><td>ff_cre_syncobj<br>ff_del_syncobj<br>ff_req_grant<br>ff_rel_grant</td><td>FF_FS_REENTRANT == 1</td><td rowspan="2">O/S dependent functions.<br>Sample code is available in ffsystem.c.</td></tr>
<tr><td>disk_write<br>get_fattime<br>disk_ioctl (CTRL_SYNC)</td><td><a href="config.html#fs_readonly">FF_FS_READONLY == 0</a></td></tr>
<tr><td>disk_ioctl (GET_SECTOR_COUNT)<br>disk_ioctl (GET_BLOCK_SIZE)</td><td><a href="config.html#use_mkfs">FF_USE_MKFS == 1</a></td></tr>
<tr><td>disk_ioctl (GET_SECTOR_SIZE)</td><td><a href="config.html#max_ss">FF_MAX_SS != FF_MIN_SS</a></td></tr>
<tr><td>disk_ioctl (CTRL_TRIM)</td><td><a href="config.html#use_trim">FF_USE_TRIM == 1</a></td></tr>
<tr><td>ff_uni2oem<br>ff_oem2uni<br>ff_wtoupper</td><td><a href="config.html#use_lfn">FF_USE_LFN != 0</a></td><td>Unicode support functions.<br>Add optional module ffunicode.c to the project.</td></tr>
<tr><td>ff_cre_syncobj<br>ff_del_syncobj<br>ff_req_grant<br>ff_rel_grant</td><td><a href="config.html#fs_reentrant">FF_FS_REENTRANT == 1</a></td><td rowspan="2">O/S dependent functions.<br>Sample code is available in ffsystem.c.</td></tr>
<tr><td>ff_mem_alloc<br>ff_mem_free</td><td>FF_USE_LFN == 3</td></tr>
</table>
<p>FatFs cares about neither what kind of storage device is used nor how it is implemented. Only a requirement is that it is a block device read/written in fixed-size blocks that accessible via the disk I/O functions defined above.</p>
@@ -103,17 +103,17 @@ The FatFs module is a middleware written in ANSI C (C89). There is no platform d
<tr><th></th><th>ARM7<small><br>32bit</small></th><th>ARM7<small><br>Thumb</small></th><th>CM3<small><br>Thumb-2</small></th><th>AVR</th><th>H8/300H</th><th>PIC24</th><th>RL78</th><th>V850ES</th><th>SH-2A</th><th>RX600</th><th>IA-32</th></tr>
<tr class="cal"> <td>Compiler</td><td>GCC</td><td>GCC</td><td>GCC</td><td>GCC</td><td>CH38</td><td>C30</td><td>CC78K0R</td><td>CA850</td><td>SHC</td><td>RXC</td><td>MSC</td></tr>
<!-- ARM Thumb CM3 AVR H8 PIC24 RL78 V850ES SH-2A RX600 IA-32 -->
<tr class="ral"><td class="cal">text (Full, R/W)</td><td>10.6k</td><td>6.8k</td><td>6.4k</td><td>12.4k</td><td>10.1k</td><td>11.4k</td><td>13.1k</td><td>8.9k</td><td>9.1k</td><td>6.5k</td><td>9.0k</td></tr>
<tr class="ral"><td class="cal">text (Min, R/W)</td> <td>7.2k</td><td>4.8k</td><td>4.6k</td> <td>8.5k</td> <td>7.1k</td> <td>8.0k</td> <td>9.6k</td><td>6.3k</td><td>6.3k</td><td>4.7k</td><td>6.4k</td></tr>
<tr class="ral"><td class="cal">text (Full, R/O)</td> <td>5.0k</td><td>3.2k</td><td>2.9k</td> <td>6.0k</td> <td>4.8k</td> <td>5.5k</td> <td>6.6k</td><td>4.4k</td><td>4.1k</td><td>3.2k</td><td>4.3k</td></tr>
<tr class="ral"><td class="cal">text (Min, R/O)</td> <td>3.8k</td><td>2.5k</td><td>2.3k</td> <td>4.4k</td> <td>3.8k</td> <td>4.2k</td> <td>5.2k</td><td>3.4k</td><td>3.3k</td><td>2.5k</td><td>3.5k</td></tr>
<tr class="ral"><td class="cal">bss</td><td>V*4 + 2</td><td>V*4 + 2</td><td>V*4 + 2</td><td>V*2 + 2</td><td>V*4 + 2</td><td>V*2 + 2</td><td>V*2 + 2</td><td>V*4 + 2</td><td>V*4 + 2</td><td>V*4 + 2</td><td>V*4 + 2</td></tr>
<tr class="ral"><td class="cal">.text (Full, R/W)</td><td>10.4k</td><td>6.7k</td><td>6.1k</td><td>12.5k</td><td>11.0k</td><td>11.6k</td><td>13.0k</td><td>8.9k</td><td>9.2k</td><td>6.5k</td><td>8.9k</td></tr>
<tr class="ral"><td class="cal">.text (Min, R/W)</td> <td>7.0k</td><td>4.7k</td><td>4.2k</td> <td>8.5k</td> <td>7.6k</td> <td>8.1k</td> <td>9.5k</td><td>6.2k</td><td>6.4k</td><td>4.6k</td><td>6.4k</td></tr>
<tr class="ral"><td class="cal">.text (Full, R/O)</td> <td>4.9k</td><td>3.2k</td><td>2.7k</td> <td>6.1k</td> <td>5.2k</td> <td>5.5k</td> <td>6.5k</td><td>4.3k</td><td>4.2k</td><td>3.2k</td><td>4.3k</td></tr>
<tr class="ral"><td class="cal">.text (Min, R/O)</td> <td>3.7k</td><td>2.5k</td><td>2.1k</td> <td>4.4k</td> <td>4.0k</td> <td>4.3k</td> <td>5.1k</td><td>3.4k</td><td>3.3k</td><td>2.5k</td><td>3.5k</td></tr>
<tr class="ral"><td class="cal">.bss</td><td>V*4 + 2</td><td>V*4 + 2</td><td>V*4 + 2</td><td>V*2 + 2</td><td>V*4 + 2</td><td>V*2 + 2</td><td>V*2 + 2</td><td>V*4 + 2</td><td>V*4 + 2</td><td>V*4 + 2</td><td>V*4 + 2</td></tr>
<tr class="ral"><td class="cal">Work area<br><small>(FF_FS_TINY == 0)</small></td><td>V*564<br>+ F*552</td><td>V*564<br>+ F*552</td><td>V*564<br>+ F*552</td><td>V*560<br>+ F*546</td><td>V*560<br>+ F*546</td><td>V*560<br>+ F*546</td><td>V*560<br>+ F*546</td><td>V*564<br>+ F*552</td><td>V*564<br>+ F*552</td><td>V*564<br>+ F*552</td><td>V*564<br>+ F*552</td></tr>
<tr class="ral"><td class="cal">Work area<br><small>(FF_FS_TINY == 1)</small></td><td>V*564<br>+ F*40</td><td>V*564<br>+ F*40</td><td>V*564<br>+ F*40</td><td>V*560<br>+ F*34</td><td>V*560<br>+ F*34</td><td>V*560<br>+ F*34</td><td>V*560<br>+ F*34</td><td>V*564<br>+ F*40</td><td>V*564<br>+ F*40</td><td>V*564<br>+ F*40</td><td>V*564<br>+ F*40</td></tr>
</table>
<p>These are the memory usage of FatFs module without lower layer on some target systems in following condition. <em>V</em> denotes number of mounted volumes and <em>F</em> denotes number of open files. Every samples here are optimezed in code size.</p>
<pre>
FatFs R0.14a options:
FatFs R0.14b options:
FF_FS_READONLY 0 (Read/Write) or 1 (Read only)
FF_FS_MINIMIZE 0 (Full, with all basic functions) or 3 (Min, with fully minimized)
FF_FS_TINY 0 (Default) or 1 (Tiny file object)
@@ -123,9 +123,9 @@ And any other options are left unchanged from original setting.
<div class="para doc" id="reduce">
<h3>Reducing Module Size</h3>
<p>Follwing table shows which API function is removed by configuration options for the module size reduction. To use any API function, the row of the function must be clear.</p>
<p>Follwing table shows which API function is removed by configuration options to reduce the module size. To use an API function, the row of the function must be clear.</p>
<table class="lst2">
<tr><td rowspan="2">Function</td><td colspan="4">FF_FS_<br>MINIMIZE</td><td colspan="2">FF_FS_<br>READONLY</td><td colspan="2">FF_USE_<br>STRFUNC</td><td colspan="3">FF_FS_<br>RPATH</td><td colspan="2">FF_USE_<br>FIND</td><td colspan="2">FF_USE_<br>CHMOD</td><td colspan="2">FF_USE_<br>EXPAND</td><td colspan="2">FF_USE_<br>LABEL</td><td colspan="2">FF_USE_<br>MKFS</td><td colspan="2">FF_USE_<br>FORWARD</td><td colspan="2">FF_MULTI_<br>PARTITION</td></tr>
<tr><td rowspan="2">Function</td><td colspan="4"><a href="config.html#fs_minimize">FF_FS_<br>MINIMIZE</a></td><td colspan="2"><a href="config.html#fs_readonly">FF_FS_<br>READONLY</a></td><td colspan="2"><a href="config.html#use_strfunc">FF_USE_<br>STRFUNC</a></td><td colspan="3"><a href="config.html#fs_rpath">FF_FS_<br>RPATH</a></td><td colspan="2"><a href="config.html#use_find">FF_USE_<br>FIND</a></td><td colspan="2"><a href="config.html#use_chmod">FF_USE_<br>CHMOD</a></td><td colspan="2"><a href="config.html#use_expand">FF_USE_<br>EXPAND</a></td><td colspan="2"><a href="config.html#use_label">FF_USE_<br>LABEL</a></td><td colspan="2"><a href="config.html#use_mkfs">FF_USE_<br>MKFS</a></td><td colspan="2"><a href="config.html#use_forward">FF_USE_<br>FORWARD</a></td><td colspan="2"><a href="config.html#multi_partition">FF_MULTI_<br>PARTITION</a></td></tr>
<tr> <td>0</td><td>1</td><td>2</td><td>3</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>1</td><td>2</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>1</td><td>0</td><td>1</td></tr>
<tr class="lst3">
<td>f_mount</td> <td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td><td> </td></tr>
@@ -166,7 +166,7 @@ And any other options are left unchanged from original setting.
<div class="para doc" id="lfn">
<h3>Long File Name</h3>
<p>FatFs module supports the long file name (LFN) extension of the FAT filesystem. The two different file names, short file name (SFN) and LFN, of a file is transparent on the API. The support for LFN feature is disabled by default. To enable the LFN, set <tt><a href="config.html#use_lfn">FF_USE_LFN</a></tt> to 1, 2 or 3, and add <tt>ffunicode.c</tt> to the project. The LFN feature requiers a certain working buffer. The buffer size can be configured by <tt><a href="config.html#max_lfn">FF_MAX_LFN</a></tt> according to the available memory. The length of an LFN can be up to 255 characters, so that the <tt>FF_MAX_LFN</tt> should be set to 255 for all existing file names. If the size of working buffer is insufficient for the input file name, the file function fails with <tt>FR_INVALID_NAME</tt>. When use any re-entry to the API with LFN feature, <tt>FF_USE_LFN</tt> must be set to 2 or 3. In this case, the file function allocates the working buffer on the stack or heap. The LFN working buffer occupies <tt>(FF_MAX_LFN + 1) * 2</tt> bytes and additional <tt>(FF_MAX_LFN + 44) / 15 * 32</tt> bytes when exFAT is enabled.</p>
<p>FatFs module supports the long file name (LFN) extension of the FAT filesystem. The two different file names, short file name (SFN) and LFN, of a file is transparent on the API. The support for LFN feature is disabled by default. To enable the LFN, set <tt><a href="config.html#use_lfn">FF_USE_LFN</a></tt> to 1, 2 or 3, and add <tt>ffunicode.c</tt> to the project. The LFN feature requiers a certain working buffer. The buffer size can be configured by <tt><a href="config.html#max_lfn">FF_MAX_LFN</a></tt> according to the available memory. The length of LFN can be up to 255 characters, so that the <tt>FF_MAX_LFN</tt> should be set to 255 for any existing file names. If the size of working buffer is insufficient for the input file name, the file function fails with <tt>FR_INVALID_NAME</tt>. When use any re-entry to the API with LFN feature in RTOS environment, <tt>FF_USE_LFN</tt> must be set to 2 or 3. In this case, the file function allocates the working buffer on the stack or heap. The LFN working buffer occupies <tt>(FF_MAX_LFN + 1) * 2</tt> bytes and additional <tt>(FF_MAX_LFN + 44) / 15 * 32</tt> bytes when exFAT is enabled.</p>
<h4>Impact upon Module Size</h4>
<table class="lst2 rset">
<caption>With LFN at CM3 + gcc</caption>
@@ -179,14 +179,14 @@ And any other options are left unchanged from original setting.
<tr><td>0 (All code pages)</td><td>+486k</td></tr>
</table>
<p>When the LFN is enabled, the module size will be increased depends on the configured code page. Right table shows the increment of code size in some code pages. Especially, in the CJK region, tens of thousands of characters are being used. Unfortunately, it requires a huge OEM-Unicode bidirectional conversion table and the module size will be drastically increased as shown in the table.</p>
<p>As the result, the FatFs with LFN enabled with DBCS code pages will not able to be ported on the most 8-bit MCU systems. If the target system is in legacy-free, in only Unicode and any ANSI/OEM code is not used at all, the code page setting gets meaningless. You will able to reduce the code size by configureing FatFs for Unicode with any SBCS code page.</p>
<p>As the result, the FatFs with LFN enabled with DBCS code pages will not able to be ported on the most 8-bit MCU systems. If the target system is in legacy-free, in only Unicode and any ANSI/OEM code is not used at all, the code page setting gets meaningless. You will able to reduce the code size by configureing FatFs for Unicode API with any SBCS code page.</p>
<p>There ware some restrictions on using LFN for open source project, because the LFN extension on the FAT filesystem was a patent of Microsoft Corporation. However the related patents all have expired and using the LFN feature is free for any projects.</p>
</div>
<div class="para doc" id="unicode">
<h3>Unicode API</h3>
<p>By default, FatFs uses ANSI/OEM code set on the API even in LFN configuration. FatFs can also switch the character encoding on the API to Unicode by configuration option <tt><a href="config.html#lfn_unicode">FF_LFN_UNICODE</a></tt>. This means that FatFs is compliant with the full featured LFN specification. The data type <tt>TCHAR</tt> specifies path name strings on the API is an alias of either <tt>char</tt>(ANSI/OEM or UTF-8), <tt>WCHAR</tt>(UTF-16) or <tt>DWORD</tt>(UTF-32) depends on that option. For more information, refer to the description in the <a href="filename.html#uni">file name</a>.</p>
<p>Note that setting of code page, <tt><a href="config.html#code_page">FF_CODE_PAGE</a></tt>, has actually no meaning when FatFs is configured for the Unicode API. It should be set 437 anyway. However it still affects code conversion of string I/O functions at <tt><a href="config.html#strf_encode">FF_STRF_ENCODE</a> == 0</tt> and backward compatibility with legacy systems, so that code page may need to be configured properly if it is considered a problem.</p>
<p>Note that setting of code page, <tt><a href="config.html#code_page">FF_CODE_PAGE</a></tt>, has actually no meaning when FatFs is configured for the Unicode API. It should be set 437 to reduce the module size. However it still affects code conversion of string I/O functions when <tt><a href="config.html#strf_encode">FF_STRF_ENCODE</a> == 0</tt>, and also backward compatibility with legacy systems. In this case, the code page may need to be configured properly if it is considered a problem.</p>
</div>
<div class="para doc" id="exfat">
@@ -198,8 +198,8 @@ And any other options are left unchanged from original setting.
<div class="para doc" id="lba64">
<h3>64-bit LBA</h3>
<p>LBA (Logical Block Addressing) is an addressing method to specify the location of data block, called sector, on the storage media. It is a simple linear address beginning from 0 as the first block of data. The host system does not need to consider how the data block is located and managed in the storage device. FatFs supports only LBA for the media access. 32-bit LBA is a common size at the interface of the most storage devices. It can address up to 2<sup>32</sup> blocks, 2 TB in 512 bytes/sector. When a storage device larger than 2 TB is used, larger sector size or 64-bit LBA will be needed to address the entire block of the storage device.</p>
<p>By default, FatFs works in 32-bit LBA for media access interface. FatFs can also switch it to 64-bit LBA by a configuration option <tt><a href="config.html#fs_lba64">FF_LBA64</a></tt>. It also enables GPT (GUID Partition Table) for partiotion management on the storage device. For further information about GPT, refer to <tt><a href="mkfs.html">f_mkfs</a></tt> and <tt><a href="fdisk.html">f_fdisk</a></tt> function.</p>
<p>LBA (Logical Block Addressing) is an addressing method to specify the location of data block, called <em>sector</em>, on the storage media. It is a simple linear address beginning from 0 as the first sector, 1 as the second sector and so on. The host system does not need to consider how the data block is located and managed in the storage device. FatFs supports only LBA for the media access. 32-bit LBA is a common size in the most LBA scheme. It can address up to 2<sup>32</sup> sectors, 2 TB in 512 bytes/sector. When a storage device larger than 2 TB is used, larger sector size or 64-bit LBA will be needed to address the entire sectors of the storage device.</p>
<p>By default, FatFs works in 32-bit LBA for media access. FatFs can also switch it to 64-bit LBA by a configuration option <tt><a href="config.html#fs_lba64">FF_LBA64</a></tt>. It also enables GPT (GUID Partition Table) for partiotion management on the storage device. For further information about GPT, refer to <tt><a href="mkfs.html">f_mkfs</a></tt> and <tt><a href="fdisk.html">f_fdisk</a></tt> function.</p>
</div>
<div class="para doc" id="reentrant">
@@ -291,9 +291,9 @@ Figure 5. Minimized critical section<br>
<h3>Various Usable Functions for FatFs Projects</h3>
<p>These are examples of extended use of FatFs APIs. New item will be added when useful code example is found.</p>
<ol>
<li><a href="http://elm-chan.org/fsw/ff/res/app1.c">Open or Create File for Append</a> (superseded by FA_APPEND flag added in R0.12)</li>
<li><a href="http://elm-chan.org/fsw/ff/res/app1.c">Open or Create File for Append</a> (superseded by FA_OPEN_APPEND flag added at R0.12)</li>
<li><a href="http://elm-chan.org/fsw/ff/res/app2.c">Delete Non-empty Sub-directory</a> (for R0.12 and later)</li>
<li><a href="http://elm-chan.org/fsw/ff/res/app3.c">Create Contiguous File</a> (superseded by f_expand function added in R0.12)</li>
<li><a href="http://elm-chan.org/fsw/ff/res/app3.c">Create Contiguous File</a> (superseded by f_expand function added at R0.12)</li>
<li><a href="http://elm-chan.org/fsw/ff/res/app5.c">Test if the File is Contiguous or Not</a></li>
<li><a href="http://elm-chan.org/fsw/ff/res/app4.c">Compatibility Checker for Storage Device Control Module</a></li>
<li><a href="http://elm-chan.org/fsw/ff/res/app6.c">Performance Checker for Storage Device Control Module</a></li>
@@ -326,7 +326,7 @@ Figure 5. Minimized critical section<br>
/ by use of this software.
/----------------------------------------------------------------------------*/
</pre>
<p>Therefore FatFs license is one of the BSD-style licenses but there is a significant feature. FatFs is mainly intended for embedded systems. In order to extend the usability for commercial products, the redistributions of FatFs in binary form, such as embedded code, binary library and any forms without source code, does not need to include about FatFs in the documentations. This is equivalent to the 1-clause BSD license. Of course FatFs is compatible with the most of open source software licenses including GNU GPL. When you redistribute the FatFs source code with any changes or create a fork, the license can also be changed to GNU GPL, BSD-style license or any open source software license that compatible with FatFs license.</p>
<p>Therefore FatFs license is one of the BSD-style licenses but there is a significant feature. FatFs is mainly intended for embedded systems. In order to extend the usability for commercial products, the redistributions of FatFs in binary form, such as embedded code, binary library and any forms without source code, does not need to include about FatFs in the documentations. This is equivalent to the 1-clause BSD license. Of course FatFs is compatible with the most of open source software licenses includs GNU GPL. When you redistribute the FatFs source code with any changes or create a fork, the license can also be changed to GNU GPL, BSD-style license or any open source software license that compatible with FatFs license.</p>
</div>
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