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diff --git a/3rdparty/fatfs-0.10b/doc/en/dread.html b/3rdparty/fatfs-0.10b/doc/en/dread.html new file mode 100644 index 00000000..3f9bc039 --- /dev/null +++ b/3rdparty/fatfs-0.10b/doc/en/dread.html @@ -0,0 +1,71 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> +<html lang="en"> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> +<meta http-equiv="Content-Style-Type" content="text/css"> +<link rel="up" title="FatFs" href="../00index_e.html"> +<link rel="alternate" hreflang="ja" title="Japanese" href="../ja/dread.html"> +<link rel="stylesheet" href="../css_e.css" type="text/css" media="screen" title="ELM Default"> +<title>FatFs - disk_read</title> +</head> + +<body> + +<div class="para func"> +<h2>disk_read</h2> +<p>The disk_read function reads sector(s) from the storage device.</p> +<pre> +DRESULT disk_read ( + BYTE <span class="arg">pdrv</span>, <span class="c">/* [IN] Physical drive number */</span> + BYTE* <span class="arg">buff</span>, <span class="c">/* [OUT] Pointer to the read data buffer */</span> + DWORD <span class="arg">sector</span>, <span class="c">/* [IN] Start sector number */</span> + UINT <span class="arg">count</span> <span class="c">/* [IN] Number of sectros to read */</span> +); +</pre> +</div> + +<div class="para arg"> +<h4>Parameters</h4> +<dl class="par"> +<dt>pdrv</dt> +<dd>Physical drive number to identify the target device.</dd> +<dt>buff</dt> +<dd>Pointer to the <em>byte array</em> to store the read data.</dd> +<dt>sector</dt> +<dd>Start sector number in logical block address (LBA).</dd> +<dt>count</dt> +<dd>Number of sectors to read. FatFs specifis it in range of from 1 to 128.</dd> +</dl> +</div> + + +<div class="para ret"> +<h4>Return Value</h4> +<dl class="ret"> +<dt>RES_OK (0)</dt> +<dd>The function succeeded.</dd> +<dt>RES_ERROR</dt> +<dd>Any hard error occured during the read operation and could not recover it.</dd> +<dt>RES_PARERR</dt> +<dd>Invalid parameter.</dd> +<dt>RES_NOTRDY</dt> +<dd>The device has not been initialized.</dd> +</dl> +</div> + + +<div class="para desc"> +<h4>Description</h4> +<p>The memory address specified by <tt class="arg">buff</tt> is not that always aligned to word boundary because the type of argument is defined as <tt>BYTE*</tt>. The misaligned read/write request can occure at <a href="appnote.html#fs1">direct transfer</a>. If the bus architecture, especially DMA controller, does not allow misaligned memory access, it should be solved in this function. There are some workarounds described below to avoid this issue.</p> +<ul> +<li>Convert word transfer to byte transfer in this function. - Recommended.</li> +<li>For <tt>f_read()</tt>, avoid long read request that includes a whole of sector. - Direct transfer will never occure.</li> +<li>For <tt>f_read(fp, buff, btr, &br)</tt>, make sure that <tt>(((UINT)buff & 3) == (f_tell(fp) & 3))</tt> is true. - Word aligned direct transfer is guaranteed.</li> +</ul> +<p>Generally, a multiple sector transfer request must not be split into single sector transactions to the storage device, or you will not get good read throughput.</p> +</div> + + +<p class="foot"><a href="../00index_e.html">Return</a></p> +</body> +</html> |