<p>On the FatFs API, most of file functions return common result code as enum type <tt>FRESULT</tt>. When a function succeeded, it returns zero, otherwise returns non-zero value that indicates type of error.</p>
<dd>An unrecoverable hard error occured in the lower layer, <tt>disk_read</tt>, <tt>disk_write</tt> or <tt>disk_ioctl</tt> function.<br>Note that if once this error occured at any operation to an open file, the file object is aborted and all operations to the file except for close will be rejected.</dd>
<dd>Assertion failed. An insanity is detected in the internal process. One of the following possibilities is suspected.
<ul>
<li>Work area (file system object, file object or etc...) has been broken by stack overflow or any other tasks. This is the reason in most case.</li>
<li>There is any error of the FAT structure on the volume.</li>
</ul>
Note that if once this error occured at any operation to an open file, the file object is aborted and all operations to the file except for close will be rejected.
<dd>The storage device cannot work due to a failure of <ahref="dinit.html"><tt>disk_initialize</tt></a> function due to no medium or any other reason.</dd>
<dd>Invalid drive number is specified in the path name. A null pointer is given as the path name. (Related option: <tt><ahref="config.html#volumes">_VOLUMES</a></tt>)</dd>
<dd>The function was canceled due to a timeout of <ahref="appnote.html#reentrant">thread-safe control</a>. (Related option: <tt><ahref="config.html#timeout">_TIMEOUT</a></tt>)</dd>
<dd>The operation to the object was rejected by <ahref="appnote.html#dup">file sharing control</a>. (Related option: <tt><ahref="config.html#fs_lock">_FS_LOCK</a></tt>)</dd>
<dd>Number of open objects has been reached maximum value and no more object can be opened. (Related option: <tt><ahref="config.html#fs_lock">_FS_LOCK</a></tt>)</dd>