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<div class="title">Device hotplug event notification</div> </div>
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<p>This page details how to use the libusb hotplug interface, where available.
<a href="#details">More...</a></p>
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="define-members"></a>
Macros</h2></td></tr>
<tr class="memitem:ga6d4f5e524a3b7ab4a25b751073335d4c"><td class="memItemLeft" align="right" valign="top"><a class="anchor" id="ga6d4f5e524a3b7ab4a25b751073335d4c"></a>
#define </td><td class="memItemRight" valign="bottom"><a class="el" href="group__hotplug.html#ga6d4f5e524a3b7ab4a25b751073335d4c">LIBUSB_HOTPLUG_MATCH_ANY</a>   -1</td></tr>
<tr class="memdesc:ga6d4f5e524a3b7ab4a25b751073335d4c"><td class="mdescLeft"> </td><td class="mdescRight">Wildcard matching for hotplug events. <br/></td></tr>
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Typedefs</h2></td></tr>
<tr class="memitem:ga4868157346bbf2c70b6af0cb0a6c0094"><td class="memItemLeft" align="right" valign="top">typedef int </td><td class="memItemRight" valign="bottom"><a class="el" href="group__hotplug.html#ga4868157346bbf2c70b6af0cb0a6c0094">libusb_hotplug_callback_handle</a></td></tr>
<tr class="memdesc:ga4868157346bbf2c70b6af0cb0a6c0094"><td class="mdescLeft"> </td><td class="mdescRight">Callback handle. <a href="#ga4868157346bbf2c70b6af0cb0a6c0094">More...</a><br/></td></tr>
<tr class="separator:ga4868157346bbf2c70b6af0cb0a6c0094"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga75a45f8de2d2ac55c6d52294af12e774"><td class="memItemLeft" align="right" valign="top">typedef int(* </td><td class="memItemRight" valign="bottom"><a class="el" href="group__hotplug.html#ga75a45f8de2d2ac55c6d52294af12e774">libusb_hotplug_callback_fn</a> )(<a class="el" href="group__lib.html#ga4ec088aa7b79c4a9599e39bf36a72833">libusb_context</a> *ctx, <a class="el" href="group__dev.html#ga77eedd00d01eb7569b880e861a971c2b">libusb_device</a> *device, <a class="el" href="group__hotplug.html#ga556d598ca379618a41bbec3597f55dcf">libusb_hotplug_event</a> event, void *user_data)</td></tr>
<tr class="memdesc:ga75a45f8de2d2ac55c6d52294af12e774"><td class="mdescLeft"> </td><td class="mdescRight">Hotplug callback function type. <a href="#ga75a45f8de2d2ac55c6d52294af12e774">More...</a><br/></td></tr>
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="enum-members"></a>
Enumerations</h2></td></tr>
<tr class="memitem:ga95ce2ec85dec177854c423cea2853c52"><td class="memItemLeft" align="right" valign="top">enum  </td><td class="memItemRight" valign="bottom"><a class="el" href="group__hotplug.html#ga95ce2ec85dec177854c423cea2853c52">libusb_hotplug_flag</a> { <a class="el" href="group__hotplug.html#gga95ce2ec85dec177854c423cea2853c52a01a1c0c9f4e6852cb6df713f2e8a7f6b">LIBUSB_HOTPLUG_ENUMERATE</a> = 1
}</td></tr>
<tr class="memdesc:ga95ce2ec85dec177854c423cea2853c52"><td class="mdescLeft"> </td><td class="mdescRight">Since version 1.0.16, <a class="el" href="group__misc.html#gaa83ecded256e0767220bcc21cc92365d">LIBUSBX_API_VERSION</a> >= 0x01000102. <a href="group__hotplug.html#ga95ce2ec85dec177854c423cea2853c52">More...</a><br/></td></tr>
<tr class="separator:ga95ce2ec85dec177854c423cea2853c52"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga556d598ca379618a41bbec3597f55dcf"><td class="memItemLeft" align="right" valign="top">enum  </td><td class="memItemRight" valign="bottom"><a class="el" href="group__hotplug.html#ga556d598ca379618a41bbec3597f55dcf">libusb_hotplug_event</a> { <a class="el" href="group__hotplug.html#gga556d598ca379618a41bbec3597f55dcfac012270cba6e08dafe7e3bec204dffd6">LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED</a> = 0x01,
<a class="el" href="group__hotplug.html#gga556d598ca379618a41bbec3597f55dcfac8234e02b673893ed549329ef3180a27">LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT</a> = 0x02
}</td></tr>
<tr class="memdesc:ga556d598ca379618a41bbec3597f55dcf"><td class="mdescLeft"> </td><td class="mdescRight">Since version 1.0.16, <a class="el" href="group__misc.html#gaa83ecded256e0767220bcc21cc92365d">LIBUSBX_API_VERSION</a> >= 0x01000102. <a href="group__hotplug.html#ga556d598ca379618a41bbec3597f55dcf">More...</a><br/></td></tr>
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:gae6c5f1add6cc754005549c7259dc35ea"><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="group__hotplug.html#gae6c5f1add6cc754005549c7259dc35ea">libusb_hotplug_register_callback</a> (<a class="el" href="group__lib.html#ga4ec088aa7b79c4a9599e39bf36a72833">libusb_context</a> *ctx, <a class="el" href="group__hotplug.html#ga556d598ca379618a41bbec3597f55dcf">libusb_hotplug_event</a> events, <a class="el" href="group__hotplug.html#ga95ce2ec85dec177854c423cea2853c52">libusb_hotplug_flag</a> flags, int vendor_id, int product_id, int dev_class, <a class="el" href="group__hotplug.html#ga75a45f8de2d2ac55c6d52294af12e774">libusb_hotplug_callback_fn</a> cb_fn, void *user_data, <a class="el" href="group__hotplug.html#ga4868157346bbf2c70b6af0cb0a6c0094">libusb_hotplug_callback_handle</a> *handle)</td></tr>
<tr class="memdesc:gae6c5f1add6cc754005549c7259dc35ea"><td class="mdescLeft"> </td><td class="mdescRight">Register a hotplug callback function. <a href="#gae6c5f1add6cc754005549c7259dc35ea">More...</a><br/></td></tr>
<tr class="separator:gae6c5f1add6cc754005549c7259dc35ea"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ga3d038cee3d9d96c4c4daf811f05f6ad3"><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="group__hotplug.html#ga3d038cee3d9d96c4c4daf811f05f6ad3">libusb_hotplug_deregister_callback</a> (<a class="el" href="group__lib.html#ga4ec088aa7b79c4a9599e39bf36a72833">libusb_context</a> *ctx, <a class="el" href="group__hotplug.html#ga4868157346bbf2c70b6af0cb0a6c0094">libusb_hotplug_callback_handle</a> handle)</td></tr>
<tr class="memdesc:ga3d038cee3d9d96c4c4daf811f05f6ad3"><td class="mdescLeft"> </td><td class="mdescRight">Deregisters a hotplug callback. <a href="#ga3d038cee3d9d96c4c4daf811f05f6ad3">More...</a><br/></td></tr>
<tr class="separator:ga3d038cee3d9d96c4c4daf811f05f6ad3"><td class="memSeparator" colspan="2"> </td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<p>This page details how to use the libusb hotplug interface, where available. </p>
<p>Be mindful that not all platforms currently implement hotplug notification and that you should first call on <a class="el" href="group__misc.html#ga9b8e324d28c624cd0b8e7ba21607b8db">libusb_has_capability()</a> with parameter <a class="el" href="group__misc.html#ggaab1b3fa0728c06fafbee897795889bd5a8b1bbccc648a6677cb9030a6ba827438">LIBUSB_CAP_HAS_HOTPLUG</a> to confirm that hotplug support is available. </p>
<h2 class="groupheader">Typedef Documentation</h2>
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<td class="memname">typedef int <a class="el" href="group__hotplug.html#ga4868157346bbf2c70b6af0cb0a6c0094">libusb_hotplug_callback_handle</a></td>
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<p>Callback handle. </p>
<p>Callbacks handles are generated by <a class="el" href="group__hotplug.html#gae6c5f1add6cc754005549c7259dc35ea" title="Register a hotplug callback function. ">libusb_hotplug_register_callback()</a> and can be used to deregister callbacks. Callback handles are unique per libusb_context and it is safe to call <a class="el" href="group__hotplug.html#ga3d038cee3d9d96c4c4daf811f05f6ad3" title="Deregisters a hotplug callback. ">libusb_hotplug_deregister_callback()</a> on an already deregisted callback.</p>
<p>Since version 1.0.16, <a class="el" href="group__misc.html#gaa83ecded256e0767220bcc21cc92365d">LIBUSBX_API_VERSION</a> >= 0x01000102</p>
<p>For more information, see <a class="el" href="hotplug.html">Device hotplug event notification</a>. </p>
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<td class="memname">typedef int( * libusb_hotplug_callback_fn)(<a class="el" href="group__lib.html#ga4ec088aa7b79c4a9599e39bf36a72833">libusb_context</a> *ctx, <a class="el" href="group__dev.html#ga77eedd00d01eb7569b880e861a971c2b">libusb_device</a> *device, <a class="el" href="group__hotplug.html#ga556d598ca379618a41bbec3597f55dcf">libusb_hotplug_event</a> event, void *user_data)</td>
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<p>Hotplug callback function type. </p>
<p>When requesting hotplug event notifications, you pass a pointer to a callback function of this type.</p>
<p>This callback may be called by an internal event thread and as such it is recommended the callback do minimal processing before returning.</p>
<p>libusbx will call this function later, when a matching event had happened on a matching device. See <a class="el" href="hotplug.html">Device hotplug event notification</a> for more information.</p>
<p>It is safe to call either <a class="el" href="group__hotplug.html#gae6c5f1add6cc754005549c7259dc35ea" title="Register a hotplug callback function. ">libusb_hotplug_register_callback()</a> or <a class="el" href="group__hotplug.html#ga3d038cee3d9d96c4c4daf811f05f6ad3" title="Deregisters a hotplug callback. ">libusb_hotplug_deregister_callback()</a> from within a callback function.</p>
<p>Since version 1.0.16, <a class="el" href="group__misc.html#gaa83ecded256e0767220bcc21cc92365d">LIBUSBX_API_VERSION</a> >= 0x01000102</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">ctx</td><td>context of this notification </td></tr>
<tr><td class="paramname">device</td><td>libusb_device this event occurred on </td></tr>
<tr><td class="paramname">event</td><td>event that occurred </td></tr>
<tr><td class="paramname">user_data</td><td>user data provided when this callback was registered </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>bool whether this callback is finished processing events. returning 1 will cause this callback to be deregistered </dd></dl>
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<h2 class="groupheader">Enumeration Type Documentation</h2>
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<td class="memname">enum <a class="el" href="group__hotplug.html#ga95ce2ec85dec177854c423cea2853c52">libusb_hotplug_flag</a></td>
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<p>Since version 1.0.16, <a class="el" href="group__misc.html#gaa83ecded256e0767220bcc21cc92365d">LIBUSBX_API_VERSION</a> >= 0x01000102. </p>
<p>Flags for hotplug events </p>
<table class="fieldtable">
<tr><th colspan="2">Enumerator</th></tr><tr><td class="fieldname"><em><a class="anchor" id="gga95ce2ec85dec177854c423cea2853c52a01a1c0c9f4e6852cb6df713f2e8a7f6b"></a>LIBUSB_HOTPLUG_ENUMERATE</em> </td><td class="fielddoc">
<p>Arm the callback and fire it for all matching currently attached devices. </p>
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<td class="memname">enum <a class="el" href="group__hotplug.html#ga556d598ca379618a41bbec3597f55dcf">libusb_hotplug_event</a></td>
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<p>Since version 1.0.16, <a class="el" href="group__misc.html#gaa83ecded256e0767220bcc21cc92365d">LIBUSBX_API_VERSION</a> >= 0x01000102. </p>
<p>Hotplug events </p>
<table class="fieldtable">
<tr><th colspan="2">Enumerator</th></tr><tr><td class="fieldname"><em><a class="anchor" id="gga556d598ca379618a41bbec3597f55dcfac012270cba6e08dafe7e3bec204dffd6"></a>LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED</em> </td><td class="fielddoc">
<p>A device has been plugged in and is ready to use. </p>
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<tr><td class="fieldname"><em><a class="anchor" id="gga556d598ca379618a41bbec3597f55dcfac8234e02b673893ed549329ef3180a27"></a>LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT</em> </td><td class="fielddoc">
<p>A device has left and is no longer available. </p>
<p>It is the user's responsibility to call libusb_close on any handle associated with a disconnected device. It is safe to call libusb_get_device_descriptor on a device that has left </p>
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<h2 class="groupheader">Function Documentation</h2>
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<td class="memname">int libusb_hotplug_register_callback </td>
<td>(</td>
<td class="paramtype"><a class="el" href="group__lib.html#ga4ec088aa7b79c4a9599e39bf36a72833">libusb_context</a> * </td>
<td class="paramname"><em>ctx</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="group__hotplug.html#ga556d598ca379618a41bbec3597f55dcf">libusb_hotplug_event</a> </td>
<td class="paramname"><em>events</em>, </td>
</tr>
<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="group__hotplug.html#ga95ce2ec85dec177854c423cea2853c52">libusb_hotplug_flag</a> </td>
<td class="paramname"><em>flags</em>, </td>
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<tr>
<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>vendor_id</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>product_id</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype">int </td>
<td class="paramname"><em>dev_class</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="group__hotplug.html#ga75a45f8de2d2ac55c6d52294af12e774">libusb_hotplug_callback_fn</a> </td>
<td class="paramname"><em>cb_fn</em>, </td>
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<td class="paramkey"></td>
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<td class="paramtype">void * </td>
<td class="paramname"><em>user_data</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="group__hotplug.html#ga4868157346bbf2c70b6af0cb0a6c0094">libusb_hotplug_callback_handle</a> * </td>
<td class="paramname"><em>handle</em> </td>
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<td>)</td>
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<p>Register a hotplug callback function. </p>
<p>Register a callback with the libusb_context. The callback will fire when a matching event occurs on a matching device. The callback is armed until either it is deregistered with <a class="el" href="group__hotplug.html#ga3d038cee3d9d96c4c4daf811f05f6ad3" title="Deregisters a hotplug callback. ">libusb_hotplug_deregister_callback()</a> or the supplied callback returns 1 to indicate it is finished processing events.</p>
<p>If the <a class="el" href="group__hotplug.html#gga95ce2ec85dec177854c423cea2853c52a01a1c0c9f4e6852cb6df713f2e8a7f6b">LIBUSB_HOTPLUG_ENUMERATE</a> is passed the callback will be called with a <a class="el" href="group__hotplug.html#gga556d598ca379618a41bbec3597f55dcfac012270cba6e08dafe7e3bec204dffd6">LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED</a> for all devices already plugged into the machine. Note that libusbx modifies its internal device list from a separate thread, while calling hotplug callbacks from <a class="el" href="group__poll.html#ga4989086e3f0327f3886a4c474ec7c327" title="Handle any pending events in blocking mode. ">libusb_handle_events()</a>, so it is possible for a device to already be present on, or removed from, its internal device list, while the hotplug callbacks still need to be dispatched. This means that when using <a class="el" href="group__hotplug.html#gga95ce2ec85dec177854c423cea2853c52a01a1c0c9f4e6852cb6df713f2e8a7f6b">LIBUSB_HOTPLUG_ENUMERATE</a>, your callback may be called twice for the arrival of the same device, once from <a class="el" href="group__hotplug.html#gae6c5f1add6cc754005549c7259dc35ea" title="Register a hotplug callback function. ">libusb_hotplug_register_callback()</a> and once from <a class="el" href="group__poll.html#ga4989086e3f0327f3886a4c474ec7c327" title="Handle any pending events in blocking mode. ">libusb_handle_events()</a>; and/or your callback may be called for the removal of a device for which an arrived call was never made.</p>
<p>Since version 1.0.16, <a class="el" href="group__misc.html#gaa83ecded256e0767220bcc21cc92365d">LIBUSBX_API_VERSION</a> >= 0x01000102</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramdir">[in]</td><td class="paramname">ctx</td><td>context to register this callback with </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">events</td><td>bitwise or of events that will trigger this callback. See <a class="el" href="group__hotplug.html#ga556d598ca379618a41bbec3597f55dcf">libusb_hotplug_event</a> </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">flags</td><td>hotplug callback flags. See <a class="el" href="group__hotplug.html#ga95ce2ec85dec177854c423cea2853c52">libusb_hotplug_flag</a> </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">vendor_id</td><td>the vendor id to match or <a class="el" href="group__hotplug.html#ga6d4f5e524a3b7ab4a25b751073335d4c">LIBUSB_HOTPLUG_MATCH_ANY</a> </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">product_id</td><td>the product id to match or <a class="el" href="group__hotplug.html#ga6d4f5e524a3b7ab4a25b751073335d4c">LIBUSB_HOTPLUG_MATCH_ANY</a> </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">dev_class</td><td>the device class to match or <a class="el" href="group__hotplug.html#ga6d4f5e524a3b7ab4a25b751073335d4c">LIBUSB_HOTPLUG_MATCH_ANY</a> </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">cb_fn</td><td>the function to be invoked on a matching event/device </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">user_data</td><td>user data to pass to the callback function </td></tr>
<tr><td class="paramdir">[out]</td><td class="paramname">handle</td><td>pointer to store the handle of the allocated callback (can be NULL) </td></tr>
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<dl class="section return"><dt>Returns</dt><dd>LIBUSB_SUCCESS on success LIBUSB_ERROR code on failure </dd></dl>
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<td class="memname">void libusb_hotplug_deregister_callback </td>
<td>(</td>
<td class="paramtype"><a class="el" href="group__lib.html#ga4ec088aa7b79c4a9599e39bf36a72833">libusb_context</a> * </td>
<td class="paramname"><em>ctx</em>, </td>
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<td class="paramtype"><a class="el" href="group__hotplug.html#ga4868157346bbf2c70b6af0cb0a6c0094">libusb_hotplug_callback_handle</a> </td>
<td class="paramname"><em>handle</em> </td>
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<p>Deregisters a hotplug callback. </p>
<p>Deregister a callback from a libusb_context. This function is safe to call from within a hotplug callback.</p>
<p>Since version 1.0.16, <a class="el" href="group__misc.html#gaa83ecded256e0767220bcc21cc92365d">LIBUSBX_API_VERSION</a> >= 0x01000102</p>
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<tr><td class="paramdir">[in]</td><td class="paramname">ctx</td><td>context this callback is registered with </td></tr>
<tr><td class="paramdir">[in]</td><td class="paramname">handle</td><td>the handle of the callback to deregister </td></tr>
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