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FatFs: Update to release R0.12c.

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Jared Boone
2017-05-03 12:39:05 +01:00
parent 85712a2c5f
commit a65fe3315c
34 changed files with 556 additions and 704 deletions
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firmware/chibios-portapack/ext/fatfs/doc/en/appnote.html
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@@ -64,7 +64,7 @@ The FatFs module assumes that size of <tt>char</tt>/<tt>short</tt>/<tt>long</tt>
<div class="para doc" id="limits">
<h3>Limits</h3>
<ul>
<li>File system type: FAT12, FAT16, FAT32(r0.0) and exFAT(r1.0).</li>
<li>File system type: FAT, FAT32(r0.0) and exFAT(r1.0).</li>
<li>Number of open files: Unlimited. (depends on available memory)</li>
<li>Number of volumes: Upto 10.</li>
<li>Volume size: Upto 2 TiB at 512 bytes/sector.</li>
@@ -144,7 +144,7 @@ And other options are left unchanged from original setting.
<div class="para doc" id="lfn">
<h3>Long File Name</h3>
<p>FatFs module supports long file name (LFN). The two different file names, short file name (SFN) and LFN, of a file is transparent on the API except for <tt>f_readdir</tt> function. The support for LFN is disabled by default. To enable the LFN, set <tt><a href="config.html#use_lfn">_USE_LFN</a></tt> to 1, 2 or 3, and add <tt>option/unicode.c</tt> to the project. The LFN requiers a certain working buffer in addition. The buffer size can be configured by <tt><a href="config.html#max_lfn">_MAX_LFN</a></tt> according to the available memory. The length of an LFN will be up to 255 characters, so that the <tt>_MAX_LFN</tt> should be set to 255 for all 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 is enabled, <tt>_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 working buffer occupies <tt>(_MAX_LFN + 1) * 2</tt> bytes and additional 608 bytes when exFAT enabled.</p>
<p>FatFs module supports long file name (LFN). The two different file names, short file name (SFN) and LFN, of a file is transparent on the API except for <tt>f_readdir</tt> function. The support for LFN is disabled by default. To enable the LFN, set <tt><a href="config.html#use_lfn">_USE_LFN</a></tt> to 1, 2 or 3, and add <tt>option/unicode.c</tt> to the project. The LFN requiers a certain working buffer in addition. The buffer size can be configured by <tt><a href="config.html#max_lfn">_MAX_LFN</a></tt> according to the available memory. The length of an LFN will be up to 255 characters, so that the <tt>_MAX_LFN</tt> should be set to 255 for all 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 is enabled, <tt>_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 working buffer occupies <tt>(_MAX_LFN + 1) * 2</tt> bytes and additional <tt>(_MAX_LFN + 44) / 15 * 32</tt> bytes when exFAT is enabled.</p>
<table class="lst2 rset">
<caption>With LFN at CM3+gcc</caption>
<tr><th><tt>_CODE_PAGE</tt></th><th>Code size</th></tr>
@@ -165,22 +165,22 @@ And other options are left unchanged from original setting.
<div class="para doc" id="exfat">
<h3>exFAT File System</h3>
<p>The exFAT (Microsoft's Extended File Allocation Table) file system is a replacement of the FAT file system which has been widely used in the embedded systems and consumer devices. It is adopted by SDA (SD Association) as a recommended file system for high capacity SD cards (&gt;32GB) and they are being shipped with this format, so that the exFAT will soon become one of the standard file systems for removable media.</p>
<p>The exFAT file system allows the file size larger than 4 GiB limit what FAT file system allows upto and some file system overhead, especially file allocation delay, are reduced as well. This feature improves the write throughput to the file. However a problem on the current implementation of FatFs is that write throughput at writing to the growing edge of the fragmented file gets less than the throughput on the FAT volume. Pre-allocating a contiguous block with <tt>f_expand</tt> function may be a workaround of this problem.</p>
<p>Note that the exFAT is a patent of Microsoft Corporation. The exFAT function of FatFs is an implementation based on US. Pat. App. Pub. No. 2009/0164440 A1. FatFs module can swich the exFAT on/off by configuration option. When enable the exFAT on the commercial products, you will need to be licensed by Microsoft depends on the final destination of the products.</p></div>
<p><em>Remark: Enabling exFAT discards C89 compatibility because of need for 64-bit integer type.</em></p>
<p>The exFAT (Microsoft's Extended File Allocation Table) file system is a replacement of the FAT file system which has been widely used in the embedded systems and consumer devices. It is adopted by SDA (SD Association) as a recommended file system for high capacity SD cards (&gt;32GB) and they are being shipped with this format, so that the exFAT become one of the standard file systems for removable media as well as FAT. The exFAT file system allows the file size larger than 4 GiB limit what FAT file system allows upto and some file system overhead, especially cluster allocation delay, are reduced as well. This feature improves the write throughput to the file.</p>
<p>Note that the exFAT is a patent of Microsoft Corporation. The exFAT function of FatFs is an implementation based on <cite>US. Pat. App. Pub. No. 2009/0164440 A1</cite>. FatFs module can swich the exFAT on/off by configuration option. When enable the exFAT on the commercial products, you will need to be licensed by Microsoft depends on the final destination of the products.</p>
<p><em>Remark: Enabling exFAT discards ANSI C (C89) compatibility because of need for 64-bit integer type.</em></p>
</div>
<div class="para doc" id="reentrant">
<h3>Re-entrancy</h3>
<p>The file operations to the different volume is always re-entrant regardless of configurations except when LFN enabled with static working buffer. It can work simultaneously without any mutual exclusion.</p>
<p>The file operations to the same volume is not re-entrant but it can also be configured thread-safe by option <tt><a href="config.html#fs_reentrant">_FS_REENTRANT</a></tt>. It enables to control exclusive use of each file system object. In this case, also the OS dependent synchronization object control functions, <tt>ff_cre_syncobj/ff_del_syncobj/ff_req_grant/ff_rel_grant</tt>, needed to be added to the project. There are some examples in the <tt>option/syscall.c</tt>.</p>
<p>The file operations to the <em>different volume</em> each other is always re-entrant regardless of configurations except when LFN enabled with static working buffer. It can work simultaneously without any mutual exclusion.</p>
<p>The file operations to the <em>same volume</em> is not re-entrant. It can also be configured thread-safe by option <tt><a href="config.html#fs_reentrant">_FS_REENTRANT</a></tt>. It enables to control exclusive use of each file system object. In this case, also the OS dependent synchronization object control functions, <tt>ff_cre_syncobj/ff_del_syncobj/ff_req_grant/ff_rel_grant</tt>, needed to be added to the project. There are some examples in the <tt>option/syscall.c</tt>.</p>
<p>When a file function is called while the volume is being accessed by other task, the file function to the volume will be suspended until that task leaves the file function. If the wait time exceeded a period defined by <tt>_TIMEOUT</tt>, the file function will abort with <tt>FR_TIMEOUT</tt>. The timeout function might not be supported on the some RTOSs.</p>
<p>There is an exception on the re-entrancy for <tt>f_mount/f_mkfs/f_fdisk</tt> function. These volume management functions are not re-entrant to the same volume and corresponding physical drive. When use these functions, other tasks need to avoid to access the volume.</p>
<p>Note that this section describes on the re-entrancy of the FatFs module itself. The <tt>_FS_REENTRANT</tt> controls only exclusive use of each file system object and it does not that prevent to re-enter the low level disk functions. For example, only <tt>disk_status</tt> function can be re-entered at single volume system and any disk function can be re-entered at multiple volume system. Thus the low level disk I/O layer must be always thread-safe when any FatFs API is re-entered by two or more tasks.</p>
<p>There is an exception on the re-entrancy for <tt>f_mount/f_mkfs/f_fdisk</tt> function. These volume management functions are not re-entrant on the same volume and corresponding physical drive. When use these functions, other tasks need to avoid to access the volume.</p>
<p>Note that this section describes on the re-entrancy of the FatFs module itself. The <tt>_FS_REENTRANT</tt> controls only exclusive use of each file system object and it does not that prevent re-entering the low level disk functions. For example, only <tt>disk_status</tt> function is re-entered at single volume system and every disk function is re-entered at multiple volume system. Thus the low level disk I/O layer must be always thread-safe when FatFs API is re-entered by two or more tasks.</p>
</div>
<div class="para doc" id="dup">
<h3>Duplicated File Access</h3>
<h3>Duplicated File Open</h3>
<p>FatFs module does not support the read/write collision control of duplicated open to a file. The duplicated open is permitted only when each of open method to a file is read mode. The duplicated open with one or more write mode to a file is always prohibited, and also open file must not be renamed or deleted. A violation of these rules can cause data colluption.</p>
<p>The file lock control can be enabled by <tt><a href="config.html#fs_lock">_FS_LOCK</a></tt> option. The value of option defines the number of open objects to manage simultaneously. In this case, if any open, rename or remove that violating the file shareing rule that described above is attempted, the file function will rejected with <tt>FR_LOCKED</tt>. If number of open objects, files and sub-directories, is equal to <tt>_FS_LOCK</tt>, an extra <tt>f_open/f_opendir</tt> function will fail with <tt>FR_TOO_MANY_OPEN_FILES</tt>.</p>
</div>
@@ -274,7 +274,7 @@ 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 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 licenses that not conflict 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 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 not conflict with FatFs license.</p>
</div>
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