libusb/hotplug.c

   1 /* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */
   2 /*
   3  * Hotplug functions for libusbx
   4  * Copyright © 2012-2013 Nathan Hjelm <hjelmn@mac.com>
   5  * Copyright © 2012-2013 Peter Stuge <peter@stuge.se>
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * This library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with this library; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include <config.h>
  23
  24 #include <errno.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #ifdef HAVE_SYS_TYPES_H
  29 #include <sys/types.h>
  30 #endif
  31 #include <assert.h>
  32
  33 #include "libusbi.h"
  34 #include "hotplug.h"
  35
  36 /**
  37  * @defgroup hotplug  Device hotplug event notification
  38  * This page details how to use the libusb hotplug interface, where available.
  39  *
  40  * Be mindful that not all platforms currently implement hotplug notification and
  41  * that you should first call on \ref libusb_has_capability() with parameter
  42  * \ref LIBUSB_CAP_HAS_HOTPLUG to confirm that hotplug support is available.
  43  *
  44  * \page hotplug Device hotplug event notification
  45  *
  46  * \section intro Introduction
  47  *
  48  * Version 1.0.16, \ref LIBUSBX_API_VERSION >= 0x01000102, has added support
  49  * for hotplug events on <b>some</b> platforms (you should test if your platform
  50  * supports hotplug notification by calling \ref libusb_has_capability() with
  51  * parameter \ref LIBUSB_CAP_HAS_HOTPLUG).
  52  *
  53  * This interface allows you to request notification for the arrival and departure
  54  * of matching USB devices.
  55  *
  56  * To receive hotplug notification you register a callback by calling
  57  * \ref libusb_hotplug_register_callback(). This function will optionally return
  58  * a handle that can be passed to \ref libusb_hotplug_deregister_callback().
  59  *
  60  * A callback function must return an int (0 or 1) indicating whether the callback is
  61  * expecting additional events. Returning 0 will rearm the callback and 1 will cause
  62  * the callback to be deregistered. Note that when callbacks are called from
  63  * libusb_hotplug_register_callback() because of the \ref LIBUSB_HOTPLUG_ENUMERATE
  64  * flag, the callback return value is ignored, iow you cannot cause a callback
  65  * to be deregistered by returning 1 when it is called from
  66  * libusb_hotplug_register_callback().
  67  *
  68  * Callbacks for a particular context are automatically deregistered by libusb_exit().
  69  *
  70  * As of 1.0.16 there are two supported hotplug events:
  71  *  - LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED: A device has arrived and is ready to use
  72  *  - LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT: A device has left and is no longer available
  73  *
  74  * A hotplug event can listen for either or both of these events.
  75  *
  76  * Note: If you receive notification that a device has left and you have any
  77  * a libusb_device_handles for the device it is up to you to call libusb_close()
  78  * on each handle to free up any remaining resources associated with the device.
  79  * Once a device has left any libusb_device_handle associated with the device
  80  * are invalid and will remain so even if the device comes back.
  81  *
  82  * When handling a LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED event it is considered
  83  * safe to call any libusbx function that takes a libusb_device. On the other hand,
  84  * when handling a LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT event the only safe function
  85  * is libusb_get_device_descriptor().
  86  *
  87  * The following code provides an example of the usage of the hotplug interface:
  88 \code
  89 static int count = 0;
  90
  91 int hotplug_callback(struct libusb_context *ctx, struct libusb_device *dev,
  92                      libusb_hotplug_event event, void *user_data) {
  93   static libusb_device_handle *handle = NULL;
  94   struct libusb_device_descriptor desc;
  95   int rc;
  96
  97   (void)libusb_get_device_descriptor(dev, &desc);
  98
  99   if (LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED == event) {
 100     rc = libusb_open(dev, &handle);
 101     if (LIBUSB_SUCCESS != rc) {
 102       printf("Could not open USB device\n");
 103     }
 104   } else if (LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT == event) {
 105     if (handle) {
 106       libusb_close(handle);
 107       handle = NULL;
 108     }
 109   } else {
 110     printf("Unhandled event %d\n", event);
 111   }
 112   count++;
 113
 114   return 0;
 115 }
 116
 117 int main (void) {
 118   libusb_hotplug_callback_handle handle;
 119   int rc;
 120
 121   libusb_init(NULL);
 122
 123   rc = libusb_hotplug_register_callback(NULL, LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED |
 124                                         LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT, 0, 0x045a, 0x5005,
 125                                         LIBUSB_HOTPLUG_MATCH_ANY, hotplug_callback, NULL,
 126                                         &handle);
 127   if (LIBUSB_SUCCESS != rc) {
 128     printf("Error creating a hotplug callback\n");
 129     libusb_exit(NULL);
 130     return EXIT_FAILURE;
 131   }
 132
 133   while (count < 2) {
 134     usleep(10000);
 135   }
 136
 137   libusb_hotplug_deregister_callback(handle);
 138   libusb_exit(NULL);
 139
 140   return 0;
 141 }
 142 \endcode
 143  */
 144
 145 static int usbi_hotplug_match_cb (struct libusb_context *ctx,
 146         struct libusb_device *dev, libusb_hotplug_event event,
 147         struct libusb_hotplug_callback *hotplug_cb)
 148 {
 149         /* Handle lazy deregistration of callback */
 150         if (hotplug_cb->needs_free) {
 151                 /* Free callback */
 152                 return 1;
 153         }
 154
 155         if (!(hotplug_cb->events & event)) {
 156                 return 0;
 157         }
 158
 159         if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->vendor_id &&
 160             hotplug_cb->vendor_id != dev->device_descriptor.idVendor) {
 161                 return 0;
 162         }
 163
 164         if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->product_id &&
 165             hotplug_cb->product_id != dev->device_descriptor.idProduct) {
 166                 return 0;
 167         }
 168
 169         if (LIBUSB_HOTPLUG_MATCH_ANY != hotplug_cb->dev_class &&
 170             hotplug_cb->dev_class != dev->device_descriptor.bDeviceClass) {
 171                 return 0;
 172         }
 173
 174         return hotplug_cb->cb (ctx, dev, event, hotplug_cb->user_data);
 175 }
 176
 177 void usbi_hotplug_match(struct libusb_context *ctx, struct libusb_device *dev,
 178         libusb_hotplug_event event)
 179 {
 180         struct libusb_hotplug_callback *hotplug_cb, *next;
 181         int ret;
 182
 183         usbi_mutex_lock(&ctx->hotplug_cbs_lock);
 184
 185         list_for_each_entry_safe(hotplug_cb, next, &ctx->hotplug_cbs, list, struct libusb_hotplug_callback) {
 186                 usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
 187                 ret = usbi_hotplug_match_cb (ctx, dev, event, hotplug_cb);
 188                 usbi_mutex_lock(&ctx->hotplug_cbs_lock);
 189
 190                 if (ret) {
 191                         list_del(&hotplug_cb->list);
 192                         free(hotplug_cb);
 193                 }
 194         }
 195
 196         usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
 197
 198         /* the backend is expected to call the callback for each active transfer */
 199 }
 200
 201 int API_EXPORTED libusb_hotplug_register_callback(libusb_context *ctx,
 202         libusb_hotplug_event events, libusb_hotplug_flag flags,
 203         int vendor_id, int product_id, int dev_class,
 204         libusb_hotplug_callback_fn cb_fn, void *user_data,
 205         libusb_hotplug_callback_handle *handle)
 206 {
 207         libusb_hotplug_callback *new_callback;
 208         static int handle_id = 1;
 209
 210         /* check for hotplug support */
 211         if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
 212                 return LIBUSB_ERROR_NOT_SUPPORTED;
 213         }
 214
 215         /* check for sane values */
 216         if ((LIBUSB_HOTPLUG_MATCH_ANY != vendor_id && (~0xffff & vendor_id)) ||
 217             (LIBUSB_HOTPLUG_MATCH_ANY != product_id && (~0xffff & product_id)) ||
 218             (LIBUSB_HOTPLUG_MATCH_ANY != dev_class && (~0xff & dev_class)) ||
 219             !cb_fn) {
 220                 return LIBUSB_ERROR_INVALID_PARAM;
 221         }
 222
 223         USBI_GET_CONTEXT(ctx);
 224
 225         new_callback = (libusb_hotplug_callback *)calloc(1, sizeof (*new_callback));
 226         if (!new_callback) {
 227                 return LIBUSB_ERROR_NO_MEM;
 228         }
 229
 230         new_callback->ctx = ctx;
 231         new_callback->vendor_id = vendor_id;
 232         new_callback->product_id = product_id;
 233         new_callback->dev_class = dev_class;
 234         new_callback->flags = flags;
 235         new_callback->events = events;
 236         new_callback->cb = cb_fn;
 237         new_callback->user_data = user_data;
 238         new_callback->needs_free = 0;
 239
 240         usbi_mutex_lock(&ctx->hotplug_cbs_lock);
 241
 242         /* protect the handle by the context hotplug lock. it doesn't matter if the same handle
 243          * is used for different contexts only that the handle is unique for this context */
 244         new_callback->handle = handle_id++;
 245
 246         list_add(&new_callback->list, &ctx->hotplug_cbs);
 247
 248         usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
 249
 250
 251         if (flags & LIBUSB_HOTPLUG_ENUMERATE) {
 252                 int i, len;
 253                 struct libusb_device **devs;
 254
 255                 len = libusb_get_device_list(ctx, &devs);
 256                 if (len < 0) {
 257                         libusb_hotplug_deregister_callback(ctx,
 258                                                         new_callback->handle);
 259                         return len;
 260                 }
 261
 262                 for (i = 0; i < len; i++) {
 263                         usbi_hotplug_match_cb(ctx, devs[i],
 264                                         LIBUSB_HOTPLUG_EVENT_DEVICE_ARRIVED,
 265                                         new_callback);
 266                 }
 267
 268                 libusb_free_device_list(devs, 1);
 269         }
 270
 271
 272         if (handle) {
 273                 *handle = new_callback->handle;
 274         }
 275
 276         return LIBUSB_SUCCESS;
 277 }
 278
 279 void API_EXPORTED libusb_hotplug_deregister_callback (struct libusb_context *ctx,
 280         libusb_hotplug_callback_handle handle)
 281 {
 282         struct libusb_hotplug_callback *hotplug_cb;
 283         libusb_hotplug_message message;
 284         ssize_t ret;
 285
 286         /* check for hotplug support */
 287         if (!libusb_has_capability(LIBUSB_CAP_HAS_HOTPLUG)) {
 288                 return;
 289         }
 290
 291         USBI_GET_CONTEXT(ctx);
 292
 293         usbi_mutex_lock(&ctx->hotplug_cbs_lock);
 294         list_for_each_entry(hotplug_cb, &ctx->hotplug_cbs, list,
 295                             struct libusb_hotplug_callback) {
 296                 if (handle == hotplug_cb->handle) {
 297                         /* Mark this callback for deregistration */
 298                         hotplug_cb->needs_free = 1;
 299                 }
 300         }
 301         usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
 302
 303         /* wakeup handle_events to do the actual free */
 304         memset(&message, 0, sizeof(message));
 305         ret = usbi_write(ctx->hotplug_pipe[1], &message, sizeof(message));
 306         if (sizeof(message) != ret) {
 307                 usbi_err(ctx, "error writing hotplug message");
 308         }
 309 }
 310
 311 void usbi_hotplug_deregister_all(struct libusb_context *ctx) {
 312         struct libusb_hotplug_callback *hotplug_cb, *next;
 313
 314         usbi_mutex_lock(&ctx->hotplug_cbs_lock);
 315         list_for_each_entry_safe(hotplug_cb, next, &ctx->hotplug_cbs, list,
 316                                  struct libusb_hotplug_callback) {
 317                 list_del(&hotplug_cb->list);
 318                 free(hotplug_cb);
 319         }
 320
 321         usbi_mutex_unlock(&ctx->hotplug_cbs_lock);
 322 }