libusb/hotplug.c - manifest_repos/libusb - Git at Google

 /* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */
 /*
  * Hotplug functions for libusb
  * Copyright © 2012-2013 Nathan Hjelm <hjelmn@mac.com>
  * Copyright © 2012-2013 Peter Stuge <peter@stuge.se>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */

 #include <config.h>

 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>
 #endif
 #include <assert.h>

 #include "libusbi.h"
 #include "hotplug.h"

 /**
  * @defgroup libusb_hotplug Device hotplug event notification
  * This page details how to use the libusb hotplug interface, where available.
  *
  * Be mindful that not all platforms currently implement hotplug notification and
  * that you should first call on \ref libusb_has_capability() with parameter
  * \ref LIBUSB_CAP_HAS_HOTPLUG to confirm that hotplug support is available.
  *
  * \page libusb_hotplug Device hotplug event notification
  *
  * \section hotplug_intro Introduction
  *
  * Version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102, has added support
  * for hotplug events on <b>some</b> platforms (you should test if your platform
  * supports hotplug notification by calling \ref libusb_has_capability() with
  * parameter \ref LIBUSB_CAP_HAS_HOTPLUG).
  *
  * This interface allows you to request notification for the arrival and departure
  * of matching USB devices.
  *
  * To receive hotplug notification you register a callback by calling
  * \ref libusb_hotplug_register_callback(). This function will optionally return
  * a callback handle that can be passed to \ref libusb_hotplug_deregister_callback().
  *
  * A callback function must return an int (0 or 1) indicating whether the callback is
  * expecting additional events. Returning 0 will rearm the callback and 1 will cause
  * the callback to be deregistered. Note that when callbacks are called from
  * libusb_hotplug_register_callback() because of the \ref LIBUSB_HOTPLUG_ENUMERATE
  * flag, the callback return value is ignored, iow you cannot cause a callback
  * to be deregistered by returning 1 when it is called from
  * libusb_hotplug_register_callback().
  *
  * Callbacks for a particular context are automatically deregistered by libusb_exit().
  *
  * As of 1.0.16 there are two supported hotplug events:
  *  - LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED: A device has arrived and is ready to use
  *  - LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT: A device has left and is no longer available
  *
  * A hotplug event can listen for either or both of these events.
  *
  * Note: If you receive notification that a device has left and you have any
  * a libusb_device_handles for the device it is up to you to call libusb_close()
  * on each device handle to free up any remaining resources associated with the device.
  * Once a device has left any libusb_device_handle associated with the device
  * are invalid and will remain so even if the device comes back.
  *
  * When handling a LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED event it is considered
  * safe to call any libusb function that takes a libusb_device. It also safe to
  * open a device and submit asynchronous transfers. However, most other functions
  * that take a libusb_device_handle are <b>not</b> safe to call. Examples of such
  * functions are any of the \ref libusb_syncio "synchronous API" functions or the blocking
  * functions that retrieve various \ref libusb_desc "USB descriptors". These functions must
  * be used outside of the context of the hotplug callback.
  *
  * When handling a LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT event the only safe function
  * is libusb_get_device_descriptor().
  *
  * The following code provides an example of the usage of the hotplug interface:
 \code
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
 #include <libusb.h>

 static int count = 0;

 int hotplug_callback(struct libusb_context *ctx, struct libusb_device *dev,
                      libusb_hotplug_event event, void *user_data) {
   static libusb_device_handle *dev_handle = NULL;
   struct libusb_device_descriptor desc;
   int rc;

   (void)libusb_get_device_descriptor(dev, &desc);

   if (LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED == event) {
     rc = libusb_open(dev, &dev_handle);
     if (LIBUSB_SUCCESS != rc) {
       printf("Could not open USB device\n");
     }
   } else if (LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT == event) {
     if (dev_handle) {
       libusb_close(dev_handle);
       dev_handle = NULL;
     }
   } else {
     printf("Unhandled event %d\n", event);
   }
   count++;

   return 0;
 }

 int main (void) {
   libusb_hotplug_callback_handle callback_handle;
   int rc;

   libusb_init(NULL);

   rc = libusb_hotplug_register_callback(NULL, LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED |
                                         LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT, 0, 0x045a, 0x5005,
                                         LIBUSB_HOTPLUG_MATCH_ANY, hotplug_callback, NULL,
                                         &callback_handle);
   if (LIBUSB_SUCCESS != rc) {
     printf("Error creating a hotplug callback\n");
     libusb_exit(NULL);
     return EXIT_FAILURE;
   }

   while (count < 2) {
     libusb_handle_events_completed(NULL, NULL);
     nanosleep(&(struct timespec){0, 10000000UL}, NULL);
   }

   libusb_hotplug_deregister_callback(NULL, callback_handle);
   libusb_exit(NULL);

   return 0;
 }
 \endcode
  */

 static int usbi_hotplug_match_cb (struct libusb_context *ctx,
 	struct libusb_device *dev, libusb_hotplug_event event,
 	struct libusb_hotplug_callback *hotplug_cb)
 {
 	/* Handle lazy deregistration of callback */
 	if (hotplug_cb->needs_free) {
 		/* Free callback */
 		return 1;
 	}

 	if (!(hotplug_cb->events & event)) {
 		return 0;
 	}

 	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->vendor_id &&
 	    hotplug_cb->vendor_id != dev->device_descriptor.idVendor) {
 		return 0;
 	}

 	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->product_id &&
 	    hotplug_cb->product_id != dev->device_descriptor.idProduct) {
 		return 0;
 	}

 	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->dev_class &&
 	    hotplug_cb->dev_class != dev->device_descriptor.bDeviceClass) {
 		return 0;
 	}

 	return hotplug_cb->cb (ctx, dev, event, hotplug_cb->user_data);
 }

 void usbi_hotplug_match(struct libusb_context *ctx, struct libusb_device *dev,
 	libusb_hotplug_event event)
 {
 	struct libusb_hotplug_callback *hotplug_cb, *next;
 	int ret;

 	usbi_mutex_lock(&ctx->hotplug_cbs_lock);

 	list_for_each_entry_safe(hotplug_cb, next, &ctx->hotplug_cbs, list, struct libusb_hotplug_callback) {
 		usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
 		ret = usbi_hotplug_match_cb (ctx, dev, event, hotplug_cb);
 		usbi_mutex_lock(&ctx->hotplug_cbs_lock);

 		if (ret) {
 			list_del(&hotplug_cb->list);
 			free(hotplug_cb);
 		}
 	}

 	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);

 	/* the backend is expected to call the callback for each active transfer */
 }

 void usbi_hotplug_notification(struct libusb_context *ctx, struct libusb_device *dev,
 	libusb_hotplug_event event)
 {
 	int pending_events;
 	libusb_hotplug_message *message = calloc(1, sizeof(*message));

 	if (!message) {
 		usbi_err(ctx, "error allocating hotplug message");
 		return;
 	}

 	message->event = event;
 	message->device = dev;

 	/* Take the event data lock and add this message to the list.
 	 * Only signal an event if there are no prior pending events. */
 	usbi_mutex_lock(&ctx->event_data_lock);
 	pending_events = usbi_pending_events(ctx);
 	list_add_tail(&message->list, &ctx->hotplug_msgs);
 	if (!pending_events)
 		usbi_signal_event(ctx);
 	usbi_mutex_unlock(&ctx->event_data_lock);
 }

 int API_EXPORTED libusb_hotplug_register_callback(libusb_context *ctx,
 	libusb_hotplug_event events, libusb_hotplug_flag flags,
 	int vendor_id, int product_id, int dev_class,
 	libusb_hotplug_callback_fn cb_fn, void *user_data,
 	libusb_hotplug_callback_handle *callback_handle)
 {
 	libusb_hotplug_callback *new_callback;
 	static int handle_id = 1;

 	/* check for hotplug support */
 	if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
 		return LIBUSB_ERROR_NOT_SUPPORTED;
 	}

 	/* check for sane values */
 	if ((LIBUSB_HOTPLUG_MATCH_ANY != vendor_id && (~0xffff & vendor_id)) ||
 	    (LIBUSB_HOTPLUG_MATCH_ANY != product_id && (~0xffff & product_id)) ||
 	    (LIBUSB_HOTPLUG_MATCH_ANY != dev_class && (~0xff & dev_class)) ||
 	    !cb_fn) {
 		return LIBUSB_ERROR_INVALID_PARAM;
 	}

 	USBI_GET_CONTEXT(ctx);

 	new_callback = (libusb_hotplug_callback *)calloc(1, sizeof (*new_callback));
 	if (!new_callback) {
 		return LIBUSB_ERROR_NO_MEM;
 	}

 	new_callback->ctx = ctx;
 	new_callback->vendor_id = vendor_id;
 	new_callback->product_id = product_id;
 	new_callback->dev_class = dev_class;
 	new_callback->flags = flags;
 	new_callback->events = events;
 	new_callback->cb = cb_fn;
 	new_callback->user_data = user_data;
 	new_callback->needs_free = 0;

 	usbi_mutex_lock(&ctx->hotplug_cbs_lock);

 	/* protect the handle by the context hotplug lock. it doesn't matter if the same handle
 	 * is used for different contexts only that the handle is unique for this context */
 	new_callback->handle = handle_id++;

 	list_add(&new_callback->list, &ctx->hotplug_cbs);

 	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);


 	if (flags & LIBUSB_HOTPLUG_ENUMERATE) {
 		int i, len;
 		struct libusb_device **devs;

 		len = (int) libusb_get_device_list(ctx, &devs);
 		if (len < 0) {
 			libusb_hotplug_deregister_callback(ctx,
 							new_callback->handle);
 			return len;
 		}

 		for (i = 0; i < len; i++) {
 			usbi_hotplug_match_cb(ctx, devs[i],
 					LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED,
 					new_callback);
 		}

 		libusb_free_device_list(devs, 1);
 	}


 	if (callback_handle)
 		*callback_handle = new_callback->handle;

 	return LIBUSB_SUCCESS;
 }

 void API_EXPORTED libusb_hotplug_deregister_callback (struct libusb_context *ctx,
 	libusb_hotplug_callback_handle callback_handle)
 {
 	struct libusb_hotplug_callback *hotplug_cb;

 	/* check for hotplug support */
 	if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
 		return;
 	}

 	USBI_GET_CONTEXT(ctx);

 	usbi_mutex_lock(&ctx->hotplug_cbs_lock);
 	list_for_each_entry(hotplug_cb, &ctx->hotplug_cbs, list,
 			    struct libusb_hotplug_callback) {
 		if (callback_handle == hotplug_cb->handle) {
 			/* Mark this callback for deregistration */
 			hotplug_cb->needs_free = 1;
 		}
 	}
 	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);

 	usbi_hotplug_notification(ctx, NULL, 0);
 }

 void usbi_hotplug_deregister_all(struct libusb_context *ctx) {
 	struct libusb_hotplug_callback *hotplug_cb, *next;

 	usbi_mutex_lock(&ctx->hotplug_cbs_lock);
 	list_for_each_entry_safe(hotplug_cb, next, &ctx->hotplug_cbs, list,
 				 struct libusb_hotplug_callback) {
 		list_del(&hotplug_cb->list);
 		free(hotplug_cb);
 	}

 	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
 }
	/* -- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -- */
	/*
	* Hotplug functions for libusb
	* Copyright © 2012-2013 Nathan Hjelm <hjelmn@mac.com>
	* Copyright © 2012-2013 Peter Stuge <peter@stuge.se>
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with this library; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	#include <config.h>

	#include <errno.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#ifdef HAVE_SYS_TYPES_H
	#include <sys/types.h>
	#endif
	#include <assert.h>

	#include "libusbi.h"
	#include "hotplug.h"

	/**
	* @defgroup libusb_hotplug Device hotplug event notification
	* This page details how to use the libusb hotplug interface, where available.
	*
	* Be mindful that not all platforms currently implement hotplug notification and
	* that you should first call on \ref libusb_has_capability() with parameter
	* \ref LIBUSB_CAP_HAS_HOTPLUG to confirm that hotplug support is available.
	*
	* \page libusb_hotplug Device hotplug event notification
	*
	* \section hotplug_intro Introduction
	*
	* Version 1.0.16, \ref LIBUSB_API_VERSION >= 0x01000102, has added support
	* for hotplug events on <b>some</b> platforms (you should test if your platform
	* supports hotplug notification by calling \ref libusb_has_capability() with
	* parameter \ref LIBUSB_CAP_HAS_HOTPLUG).
	*
	* This interface allows you to request notification for the arrival and departure
	* of matching USB devices.
	*
	* To receive hotplug notification you register a callback by calling
	* \ref libusb_hotplug_register_callback(). This function will optionally return
	* a callback handle that can be passed to \ref libusb_hotplug_deregister_callback().
	*
	* A callback function must return an int (0 or 1) indicating whether the callback is
	* expecting additional events. Returning 0 will rearm the callback and 1 will cause
	* the callback to be deregistered. Note that when callbacks are called from
	* libusb_hotplug_register_callback() because of the \ref LIBUSB_HOTPLUG_ENUMERATE
	* flag, the callback return value is ignored, iow you cannot cause a callback
	* to be deregistered by returning 1 when it is called from
	* libusb_hotplug_register_callback().
	*
	* Callbacks for a particular context are automatically deregistered by libusb_exit().
	*
	* As of 1.0.16 there are two supported hotplug events:
	* - LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED: A device has arrived and is ready to use
	* - LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT: A device has left and is no longer available
	*
	* A hotplug event can listen for either or both of these events.
	*
	* Note: If you receive notification that a device has left and you have any
	* a libusb_device_handles for the device it is up to you to call libusb_close()
	* on each device handle to free up any remaining resources associated with the device.
	* Once a device has left any libusb_device_handle associated with the device
	* are invalid and will remain so even if the device comes back.
	*
	* When handling a LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED event it is considered
	* safe to call any libusb function that takes a libusb_device. It also safe to
	* open a device and submit asynchronous transfers. However, most other functions
	* that take a libusb_device_handle are <b>not</b> safe to call. Examples of such
	* functions are any of the \ref libusb_syncio "synchronous API" functions or the blocking
	* functions that retrieve various \ref libusb_desc "USB descriptors". These functions must
	* be used outside of the context of the hotplug callback.
	*
	* When handling a LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT event the only safe function
	* is libusb_get_device_descriptor().
	*
	* The following code provides an example of the usage of the hotplug interface:
	\code
	#include <stdio.h>
	#include <stdlib.h>
	#include <time.h>
	#include <libusb.h>

	static int count = 0;

	int hotplug_callback(struct libusb_context ctx, struct libusb_device dev,
	libusb_hotplug_event event, void *user_data) {
	static libusb_device_handle *dev_handle = NULL;
	struct libusb_device_descriptor desc;
	int rc;

	(void)libusb_get_device_descriptor(dev, &desc);

	if (LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED == event) {
	rc = libusb_open(dev, &dev_handle);
	if (LIBUSB_SUCCESS != rc) {
	printf("Could not open USB device\n");
	}
	} else if (LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT == event) {
	if (dev_handle) {
	libusb_close(dev_handle);
	dev_handle = NULL;
	}
	} else {
	printf("Unhandled event %d\n", event);
	}
	count++;

	return 0;
	}

	int main (void) {
	libusb_hotplug_callback_handle callback_handle;
	int rc;

	libusb_init(NULL);

	rc = libusb_hotplug_register_callback(NULL, LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED \|
	LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT, 0, 0x045a, 0x5005,
	LIBUSB_HOTPLUG_MATCH_ANY, hotplug_callback, NULL,
	&callback_handle);
	if (LIBUSB_SUCCESS != rc) {
	printf("Error creating a hotplug callback\n");
	libusb_exit(NULL);
	return EXIT_FAILURE;
	}

	while (count < 2) {
	libusb_handle_events_completed(NULL, NULL);
	nanosleep(&(struct timespec){0, 10000000UL}, NULL);
	}

	libusb_hotplug_deregister_callback(NULL, callback_handle);
	libusb_exit(NULL);

	return 0;
	}
	\endcode
	*/

	static int usbi_hotplug_match_cb (struct libusb_context *ctx,
	struct libusb_device *dev, libusb_hotplug_event event,
	struct libusb_hotplug_callback *hotplug_cb)
	{
	/* Handle lazy deregistration of callback */
	if (hotplug_cb->needs_free) {
	/* Free callback */
	return 1;
	}

	if (!(hotplug_cb->events & event)) {
	return 0;
	}

	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->vendor_id &&
	hotplug_cb->vendor_id != dev->device_descriptor.idVendor) {
	return 0;
	}

	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->product_id &&
	hotplug_cb->product_id != dev->device_descriptor.idProduct) {
	return 0;
	}

	if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->dev_class &&
	hotplug_cb->dev_class != dev->device_descriptor.bDeviceClass) {
	return 0;
	}

	return hotplug_cb->cb (ctx, dev, event, hotplug_cb->user_data);
	}

	void usbi_hotplug_match(struct libusb_context ctx, struct libusb_device dev,
	libusb_hotplug_event event)
	{
	struct libusb_hotplug_callback hotplug_cb, next;
	int ret;

	usbi_mutex_lock(&ctx->hotplug_cbs_lock);

	list_for_each_entry_safe(hotplug_cb, next, &ctx->hotplug_cbs, list, struct libusb_hotplug_callback) {
	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
	ret = usbi_hotplug_match_cb (ctx, dev, event, hotplug_cb);
	usbi_mutex_lock(&ctx->hotplug_cbs_lock);

	if (ret) {
	list_del(&hotplug_cb->list);
	free(hotplug_cb);
	}
	}

	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);

	/* the backend is expected to call the callback for each active transfer */
	}

	void usbi_hotplug_notification(struct libusb_context ctx, struct libusb_device dev,
	libusb_hotplug_event event)
	{
	int pending_events;
	libusb_hotplug_message message = calloc(1, sizeof(message));

	if (!message) {
	usbi_err(ctx, "error allocating hotplug message");
	return;
	}

	message->event = event;
	message->device = dev;

	/* Take the event data lock and add this message to the list.
	* Only signal an event if there are no prior pending events. */
	usbi_mutex_lock(&ctx->event_data_lock);
	pending_events = usbi_pending_events(ctx);
	list_add_tail(&message->list, &ctx->hotplug_msgs);
	if (!pending_events)
	usbi_signal_event(ctx);
	usbi_mutex_unlock(&ctx->event_data_lock);
	}

	int API_EXPORTED libusb_hotplug_register_callback(libusb_context *ctx,
	libusb_hotplug_event events, libusb_hotplug_flag flags,
	int vendor_id, int product_id, int dev_class,
	libusb_hotplug_callback_fn cb_fn, void *user_data,
	libusb_hotplug_callback_handle *callback_handle)
	{
	libusb_hotplug_callback *new_callback;
	static int handle_id = 1;

	/* check for hotplug support */
	if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
	return LIBUSB_ERROR_NOT_SUPPORTED;
	}

	/* check for sane values */
	if ((LIBUSB_HOTPLUG_MATCH_ANY != vendor_id && (~0xffff & vendor_id)) \|\|
	(LIBUSB_HOTPLUG_MATCH_ANY != product_id && (~0xffff & product_id)) \|\|
	(LIBUSB_HOTPLUG_MATCH_ANY != dev_class && (~0xff & dev_class)) \|\|
	!cb_fn) {
	return LIBUSB_ERROR_INVALID_PARAM;
	}

	USBI_GET_CONTEXT(ctx);

	new_callback = (libusb_hotplug_callback )calloc(1, sizeof (new_callback));
	if (!new_callback) {
	return LIBUSB_ERROR_NO_MEM;
	}

	new_callback->ctx = ctx;
	new_callback->vendor_id = vendor_id;
	new_callback->product_id = product_id;
	new_callback->dev_class = dev_class;
	new_callback->flags = flags;
	new_callback->events = events;
	new_callback->cb = cb_fn;
	new_callback->user_data = user_data;
	new_callback->needs_free = 0;

	usbi_mutex_lock(&ctx->hotplug_cbs_lock);

	/* protect the handle by the context hotplug lock. it doesn't matter if the same handle
	* is used for different contexts only that the handle is unique for this context */
	new_callback->handle = handle_id++;

	list_add(&new_callback->list, &ctx->hotplug_cbs);

	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);


	if (flags & LIBUSB_HOTPLUG_ENUMERATE) {
	int i, len;
	struct libusb_device **devs;

	len = (int) libusb_get_device_list(ctx, &devs);
	if (len < 0) {
	libusb_hotplug_deregister_callback(ctx,
	new_callback->handle);
	return len;
	}

	for (i = 0; i < len; i++) {
	usbi_hotplug_match_cb(ctx, devs[i],
	LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED,
	new_callback);
	}

	libusb_free_device_list(devs, 1);
	}


	if (callback_handle)
	*callback_handle = new_callback->handle;

	return LIBUSB_SUCCESS;
	}

	void API_EXPORTED libusb_hotplug_deregister_callback (struct libusb_context *ctx,
	libusb_hotplug_callback_handle callback_handle)
	{
	struct libusb_hotplug_callback *hotplug_cb;

	/* check for hotplug support */
	if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
	return;
	}

	USBI_GET_CONTEXT(ctx);

	usbi_mutex_lock(&ctx->hotplug_cbs_lock);
	list_for_each_entry(hotplug_cb, &ctx->hotplug_cbs, list,
	struct libusb_hotplug_callback) {
	if (callback_handle == hotplug_cb->handle) {
	/* Mark this callback for deregistration */
	hotplug_cb->needs_free = 1;
	}
	}
	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);

	usbi_hotplug_notification(ctx, NULL, 0);
	}

	void usbi_hotplug_deregister_all(struct libusb_context *ctx) {
	struct libusb_hotplug_callback hotplug_cb, next;

	usbi_mutex_lock(&ctx->hotplug_cbs_lock);
	list_for_each_entry_safe(hotplug_cb, next, &ctx->hotplug_cbs, list,
	struct libusb_hotplug_callback) {
	list_del(&hotplug_cb->list);
	free(hotplug_cb);
	}

	usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
	}