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<table class="head">
<tr>
<td class="head-ltitle">SMB(4)</td>
<td class="head-vol">Device Drivers Manual</td>
<td class="head-rtitle">SMB(4)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">smb</code> — <span class="Nd">System
Management Bus (SMBus) generic I/O device driver</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="Cd">device smb</code></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The
<a class="permalink" href="#smb"><i class="Em" id="smb">smb</i></a>
character device driver provides generic I/O to any
<a class="Xr">smbus(4)</a> instance. To control SMB devices, use
<span class="Pa">/dev/smb?</span> with the ioctls described below. Any of
these ioctl commands takes a pointer to <var class="Vt">struct smbcmd</var>
as its argument.</p>
<div class="Bd Pp Li">
<pre>#include <sys/types.h>
struct smbcmd {
u_char cmd;
u_char reserved;
u_short op;
union {
char byte;
char buf[2];
short word;
} wdata;
union {
char byte;
char buf[2];
short word;
} rdata;
int slave;
char *wbuf; /* use wdata if NULL */
int wcount;
char *rbuf; /* use rdata if NULL */
int rcount;
};</pre>
</div>
<p class="Pp">The <var class="Fa">slave</var> field is always used, and provides
the address of the SMBus slave device. The slave address is specified in the
seven most significant bits (i.e., “left-justified”). The
least significant bit of the slave address must be zero.</p>
<p class="Pp"></p>
<table class="Bl-column Bl-compact">
<tr id="Ioctl">
<td><a class="permalink" href="#Ioctl"><i class="Em">Ioctl</i></a></td>
<td><a class="permalink" href="#Description"><i class="Em" id="Description">Description</i></a>
<p class="Pp"></p>
</td>
</tr>
<tr id="SMB_QUICK_WRITE">
<td><a class="permalink" href="#SMB_QUICK_WRITE"><code class="Dv">SMB_QUICK_WRITE</code></a></td>
<td><a class="permalink" href="#QuickWrite"><i class="Em" id="QuickWrite">QuickWrite</i></a>
does not transfer any data. It just issues the device address with write
intent to the bus.</td>
</tr>
<tr id="SMB_QUICK_READ">
<td><a class="permalink" href="#SMB_QUICK_READ"><code class="Dv">SMB_QUICK_READ</code></a></td>
<td><a class="permalink" href="#QuickRead"><i class="Em" id="QuickRead">QuickRead</i></a>
does not transfer any data. It just issues the device address with read
intent to the bus.</td>
</tr>
<tr id="SMB_SENDB">
<td><a class="permalink" href="#SMB_SENDB"><code class="Dv">SMB_SENDB</code></a></td>
<td><a class="permalink" href="#SendByte"><i class="Em" id="SendByte">SendByte</i></a>
sends the byte provided in <var class="Fa">cmd</var> to the device.</td>
</tr>
<tr id="SMB_RECVB">
<td><a class="permalink" href="#SMB_RECVB"><code class="Dv">SMB_RECVB</code></a></td>
<td><a class="permalink" href="#ReceiveByte"><i class="Em" id="ReceiveByte">ReceiveByte</i></a>
reads a single byte from the device which is returned in
<var class="Fa">cmd</var>.</td>
</tr>
<tr id="SMB_WRITEB">
<td><a class="permalink" href="#SMB_WRITEB"><code class="Dv">SMB_WRITEB</code></a></td>
<td><a class="permalink" href="#WriteByte"><i class="Em" id="WriteByte">WriteByte</i></a>
first sends the byte from <var class="Fa">cmd</var> to the device,
followed by the byte given in <var class="Fa">wdata.byte</var>.</td>
</tr>
<tr id="SMB_WRITEW">
<td><a class="permalink" href="#SMB_WRITEW"><code class="Dv">SMB_WRITEW</code></a></td>
<td><a class="permalink" href="#WriteWord"><i class="Em" id="WriteWord">WriteWord</i></a>
first sends the byte from <var class="Fa">cmd</var> to the device,
followed by the word given in <var class="Fa">wdata.word</var>. Note that
the SMBus byte-order is little-endian by definition.</td>
</tr>
<tr id="SMB_READB">
<td><a class="permalink" href="#SMB_READB"><code class="Dv">SMB_READB</code></a></td>
<td><a class="permalink" href="#ReadByte"><i class="Em" id="ReadByte">ReadByte</i></a>
first sends the byte from <var class="Fa">cmd</var> to the device, then
reads one byte of data from the device. Returned data is stored in
<var class="Fa">rdata.byte</var>.</td>
</tr>
<tr id="SMB_READW">
<td><a class="permalink" href="#SMB_READW"><code class="Dv">SMB_READW</code></a></td>
<td><a class="permalink" href="#ReadWord"><i class="Em" id="ReadWord">ReadWord</i></a>
first sends the byte from <var class="Fa">cmd</var> to the device, then
reads one word of data from the device. Returned data is stored in
<var class="Fa">rdata.word</var>.</td>
</tr>
<tr id="SMB_PCALL">
<td><a class="permalink" href="#SMB_PCALL"><code class="Dv">SMB_PCALL</code></a></td>
<td><a class="permalink" href="#ProcedureCall"><i class="Em" id="ProcedureCall">ProcedureCall</i></a>
first sends the byte from <var class="Fa">cmd</var> to the device,
followed by the word provided in <var class="Fa">wdata.word</var>. It then
reads one word of data from the device and returns it in
<var class="Fa">rdata.word</var>.</td>
</tr>
<tr id="SMB_BWRITE">
<td><a class="permalink" href="#SMB_BWRITE"><code class="Dv">SMB_BWRITE</code></a></td>
<td><a class="permalink" href="#BlockWrite"><i class="Em" id="BlockWrite">BlockWrite</i></a>
first sends the byte from <var class="Fa">cmd</var> to the device, then
the byte from <var class="Fa">wcount</var> followed by
<var class="Fa">wcount</var> bytes of data that are taken from the buffer
pointed to by <var class="Fa">wbuf</var>. The SMBus specification mandates
that no more than 32 bytes of data can be transferred in a single block
read or write command. This value can be read from the constant
<code class="Dv">SMB_MAXBLOCKSIZE</code>.</td>
</tr>
<tr id="SMB_BREAD">
<td><a class="permalink" href="#SMB_BREAD"><code class="Dv">SMB_BREAD</code></a></td>
<td><a class="permalink" href="#BlockRead"><i class="Em" id="BlockRead">BlockRead</i></a>
first sends the byte from <var class="Fa">cmd</var> to the device, then
reads a count of data bytes that the device is going to provide and then
reads that many bytes. The count is returned in
<var class="Fa">rcount</var>. The data is returned in the buffer pointed
to by <var class="Fa">rbuf</var>.</td>
</tr>
</table>
<p class="Pp">The <a class="Xr">read(2)</a> and <a class="Xr">write(2)</a>
system calls are not implemented by this driver.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="ERRORS"><a class="permalink" href="#ERRORS">ERRORS</a></h1>
<p class="Pp">The <a class="Xr">ioctl(2)</a> commands can cause the following
driver-specific errors:</p>
<dl class="Bl-tag">
<dt id="ENXIO">[<a class="permalink" href="#ENXIO"><code class="Er">ENXIO</code></a>]</dt>
<dd>Device did not respond to selection.</dd>
<dt id="EBUSY">[<a class="permalink" href="#EBUSY"><code class="Er">EBUSY</code></a>]</dt>
<dd>Device still in use.</dd>
<dt id="ENODEV">[<a class="permalink" href="#ENODEV"><code class="Er">ENODEV</code></a>]</dt>
<dd>Operation not supported by device (not supposed to happen).</dd>
<dt id="EINVAL">[<a class="permalink" href="#EINVAL"><code class="Er">EINVAL</code></a>]</dt>
<dd>General argument error.</dd>
<dt id="EWOULDBLOCK">[<a class="permalink" href="#EWOULDBLOCK"><code class="Er">EWOULDBLOCK</code></a>]</dt>
<dd>SMBus transaction timed out.</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">ioctl(2)</a>, <a class="Xr">smbus(4)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">smb</code> manual page first appeared in
<span class="Ux">FreeBSD 3.0</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<p class="Pp">This manual page was written by <span class="An">Nicolas
Souchu</span> and extended by
<br/>
<span class="An">Michael Gmelin</span> ⟨freebsd@grem.de⟩.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">April 25, 2015</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
