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<table class="head">
<tr>
<td class="head-ltitle">DEVFS_CDEVPRIV(9)</td>
<td class="head-vol">Kernel Developer's Manual</td>
<td class="head-rtitle">DEVFS_CDEVPRIV(9)</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">devfs_set_cdevpriv</code>,
<code class="Nm">devfs_get_cdevpriv</code>,
<code class="Nm">devfs_clear_cdevpriv</code>,
<code class="Nm">devfs_foreach_cdevpriv</code> —
<span class="Nd">manage per-open filedescriptor data for devices</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="In">#include
<<a class="In">sys/param.h</a>></code>
<br/>
<code class="In">#include <<a class="In">sys/conf.h</a>></code></p>
<div class="Bd Pp Li">
<pre>typedef void d_priv_dtor_t(void *data);</pre>
</div>
<br/>
<var class="Ft">int</var>
<br/>
<code class="Fn">devfs_get_cdevpriv</code>(<var class="Fa" style="white-space: nowrap;">void
**datap</var>);
<p class="Pp"><var class="Ft">int</var>
<br/>
<code class="Fn">devfs_set_cdevpriv</code>(<var class="Fa" style="white-space: nowrap;">void
*priv</var>, <var class="Fa" style="white-space: nowrap;">d_priv_dtor_t
*dtr</var>);</p>
<p class="Pp"><var class="Ft">void</var>
<br/>
<code class="Fn">devfs_clear_cdevpriv</code>(<var class="Fa" style="white-space: nowrap;">void</var>);</p>
<p class="Pp"><var class="Ft">int</var>
<br/>
<code class="Fn">devfs_foreach_cdevpriv</code>(<var class="Fa">struct cdev
*dev</var>, <var class="Fa">int (*cb)(void *data, void *arg)</var>,
<var class="Fa">void *arg</var>);</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="#devfs_xxx_cdevpriv"><code class="Fn" id="devfs_xxx_cdevpriv">devfs_xxx_cdevpriv</code></a>()
family of functions allows the <var class="Fa">cdev</var> driver methods to
associate some driver-specific data with each user process
<a class="Xr">open(2)</a> of the device special file. Currently, functioning
of these functions is restricted to the context of the
<var class="Fa">cdevsw</var> switch method calls performed as
<a class="Xr">devfs(4)</a> operations in response to system calls that use
filedescriptors.</p>
<p class="Pp" id="devfs_set_cdevpriv">The
<a class="permalink" href="#devfs_set_cdevpriv"><code class="Fn">devfs_set_cdevpriv</code></a>()
function associates a data pointed by <var class="Va">priv</var> with
current calling context (filedescriptor). The data may be retrieved later,
possibly from another call performed on this filedescriptor, by the
<code class="Fn">devfs_get_cdevpriv</code>() function. The
<code class="Fn">devfs_clear_cdevpriv</code>() disassociates previously
attached data from context. Immediately after
<code class="Fn">devfs_clear_cdevpriv</code>() finished operating, the
<var class="Va">dtr</var> callback is called, with private data supplied
<var class="Va">data</var> argument. The
<code class="Fn">devfs_clear_cdevpriv</code>() function will be also be
called if the open callback function returns an error code.</p>
<p class="Pp" id="devfs_clear_cdevpriv">On the last filedescriptor close, system
automatically arranges
<a class="permalink" href="#devfs_clear_cdevpriv"><code class="Fn">devfs_clear_cdevpriv</code></a>()
call.</p>
<p class="Pp">If successful, the functions return 0.</p>
<p class="Pp" id="devfs_set_cdevpriv~2">The function
<a class="permalink" href="#devfs_set_cdevpriv~2"><code class="Fn">devfs_set_cdevpriv</code></a>()
returns the following values on error:</p>
<dl class="Bl-tag">
<dt>[<code class="Er">ENOENT</code>]</dt>
<dd>The current call is not associated with some filedescriptor.</dd>
<dt>[<code class="Er">EBUSY</code>]</dt>
<dd>The private driver data is already associated with current
filedescriptor.</dd>
</dl>
<p class="Pp" id="devfs_get_cdevpriv">The function
<a class="permalink" href="#devfs_get_cdevpriv"><code class="Fn">devfs_get_cdevpriv</code></a>()
returns the following values on error:</p>
<dl class="Bl-tag">
<dt>[<code class="Er">EBADF</code>]</dt>
<dd>The current call is not associated with some filedescriptor.</dd>
<dt>[<code class="Er">ENOENT</code>]</dt>
<dd>The private driver data was not associated with current filedescriptor, or
<code class="Fn">devfs_clear_cdevpriv</code>() was called.</dd>
</dl>
<p class="Pp" id="devfs_foreach_cdevpriv">The function
<a class="permalink" href="#devfs_foreach_cdevpriv"><code class="Fn">devfs_foreach_cdevpriv</code></a>()
sequentially calls the function <var class="Fa">cb</var> for each
<code class="Nm">cdevpriv</code> structure, currently associated with the
<var class="Fa">cdev</var> device. The iterated
<code class="Nm">cdevpriv</code> data pointer and the user-supplied context
<var class="Fa">arg</var> are passed to the function
<var class="Fa">cb</var>. If <var class="Fa">cb</var> returns non-zero
value, the iteration stops on that element. The
<code class="Fn">devfs_foreach_cdevpriv</code>() returns the return value
from the last call to <var class="Fa">cb</var>, or zero if no
<code class="Nm">cdevpriv</code> data is currently associated with the
device.</p>
<p class="Pp">Current implementation of the iterator makes it impossible to use
any blockable locking inside the callback <var class="Fa">cb</var>.</p>
</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">close(2)</a>, <a class="Xr">open(2)</a>,
<a class="Xr">devfs(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="Fn">devfs_cdevpriv</code>() family of functions
first appeared in <span class="Ux">FreeBSD 7.1</span>.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">March 23, 2024</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
