drivers/connector/connector.c

   1 /*
   2  *      connector.c
   3  *
   4  * 2004-2005 Copyright (c) Evgeniy Polyakov <johnpol@2ka.mipt.ru>
   5  * All rights reserved.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program 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
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/module.h>
  24 #include <linux/list.h>
  25 #include <linux/skbuff.h>
  26 #include <linux/netlink.h>
  27 #include <linux/moduleparam.h>
  28 #include <linux/connector.h>
  29 #include <linux/mutex.h>
  30
  31 #include <net/sock.h>
  32
  33 MODULE_LICENSE("GPL");
  34 MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
  35 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
  36
  37 static u32 cn_idx = CN_IDX_CONNECTOR;
  38 static u32 cn_val = CN_VAL_CONNECTOR;
  39
  40 module_param(cn_idx, uint, 0);
  41 module_param(cn_val, uint, 0);
  42 MODULE_PARM_DESC(cn_idx, "Connector's main device idx.");
  43 MODULE_PARM_DESC(cn_val, "Connector's main device val.");
  44
  45 static DEFINE_MUTEX(notify_lock);
  46 static LIST_HEAD(notify_list);
  47
  48 static struct cn_dev cdev;
  49
  50 static int cn_already_initialized;
  51
  52 /*
  53  * msg->seq and msg->ack are used to determine message genealogy.
  54  * When someone sends message it puts there locally unique sequence
  55  * and random acknowledge numbers.  Sequence number may be copied into
  56  * nlmsghdr->nlmsg_seq too.
  57  *
  58  * Sequence number is incremented with each message to be sent.
  59  *
  60  * If we expect reply to our message then the sequence number in
  61  * received message MUST be the same as in original message, and
  62  * acknowledge number MUST be the same + 1.
  63  *
  64  * If we receive a message and its sequence number is not equal to the
  65  * one we are expecting then it is a new message.
  66  *
  67  * If we receive a message and its sequence number is the same as one
  68  * we are expecting but it's acknowledgement number is not equal to
  69  * the acknowledgement number in the original message + 1, then it is
  70  * a new message.
  71  *
  72  */
  73 int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
  74 {
  75         struct cn_callback_entry *__cbq;
  76         unsigned int size;
  77         struct sk_buff *skb;
  78         struct nlmsghdr *nlh;
  79         struct cn_msg *data;
  80         struct cn_dev *dev = &cdev;
  81         u32 group = 0;
  82         int found = 0;
  83
  84         if (!__group) {
  85                 spin_lock_bh(&dev->cbdev->queue_lock);
  86                 list_for_each_entry(__cbq, &dev->cbdev->queue_list,
  87                                     callback_entry) {
  88                         if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
  89                                 found = 1;
  90                                 group = __cbq->group;
  91                                 break;
  92                         }
  93                 }
  94                 spin_unlock_bh(&dev->cbdev->queue_lock);
  95
  96                 if (!found)
  97                         return -ENODEV;
  98         } else {
  99                 group = __group;
 100         }
 101
 102         if (!netlink_has_listeners(dev->nls, group))
 103                 return -ESRCH;
 104
 105         size = NLMSG_SPACE(sizeof(*msg) + msg->len);
 106
 107         skb = alloc_skb(size, gfp_mask);
 108         if (!skb)
 109                 return -ENOMEM;
 110
 111         nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
 112
 113         data = NLMSG_DATA(nlh);
 114
 115         memcpy(data, msg, sizeof(*data) + msg->len);
 116
 117         NETLINK_CB(skb).dst_group = group;
 118
 119         return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);
 120
 121 nlmsg_failure:
 122         kfree_skb(skb);
 123         return -EINVAL;
 124 }
 125 EXPORT_SYMBOL_GPL(cn_netlink_send);
 126
 127 /*
 128  * Callback helper - queues work and setup destructor for given data.
 129  */
 130 static int cn_call_callback(struct cn_msg *msg, void (*destruct_data)(void *), void *data)
 131 {
 132         struct cn_callback_entry *__cbq, *__new_cbq;
 133         struct cn_dev *dev = &cdev;
 134         int err = -ENODEV;
 135
 136         spin_lock_bh(&dev->cbdev->queue_lock);
 137         list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
 138                 if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
 139                         if (likely(!work_pending(&__cbq->work) &&
 140                                         __cbq->data.ddata == NULL)) {
 141                                 __cbq->data.callback_priv = msg;
 142
 143                                 __cbq->data.ddata = data;
 144                                 __cbq->data.destruct_data = destruct_data;
 145
 146                                 if (queue_work(dev->cbdev->cn_queue,
 147                                                         &__cbq->work))
 148                                         err = 0;
 149                                 else
 150                                         err = -EINVAL;
 151                         } else {
 152                                 struct cn_callback_data *d;
 153
 154                                 err = -ENOMEM;
 155                                 __new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
 156                                 if (__new_cbq) {
 157                                         d = &__new_cbq->data;
 158                                         d->callback_priv = msg;
 159                                         d->callback = __cbq->data.callback;
 160                                         d->ddata = data;
 161                                         d->destruct_data = destruct_data;
 162                                         d->free = __new_cbq;
 163
 164                                         INIT_WORK(&__new_cbq->work,
 165                                                         &cn_queue_wrapper);
 166
 167                                         if (queue_work(dev->cbdev->cn_queue,
 168                                                     &__new_cbq->work))
 169                                                 err = 0;
 170                                         else {
 171                                                 kfree(__new_cbq);
 172                                                 err = -EINVAL;
 173                                         }
 174                                 }
 175                         }
 176                         break;
 177                 }
 178         }
 179         spin_unlock_bh(&dev->cbdev->queue_lock);
 180
 181         return err;
 182 }
 183
 184 /*
 185  * Main netlink receiving function.
 186  *
 187  * It checks skb, netlink header and msg sizes, and calls callback helper.
 188  */
 189 static void cn_rx_skb(struct sk_buff *__skb)
 190 {
 191         struct cn_msg *msg;
 192         struct nlmsghdr *nlh;
 193         int err;
 194         struct sk_buff *skb;
 195
 196         skb = skb_get(__skb);
 197
 198         if (skb->len >= NLMSG_SPACE(0)) {
 199                 nlh = nlmsg_hdr(skb);
 200
 201                 if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
 202                     skb->len < nlh->nlmsg_len ||
 203                     nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
 204                         kfree_skb(skb);
 205                         return;
 206                 }
 207
 208                 msg = NLMSG_DATA(nlh);
 209                 err = cn_call_callback(msg, (void (*)(void *))kfree_skb, skb);
 210                 if (err < 0)
 211                         kfree_skb(skb);
 212         }
 213 }
 214
 215 /*
 216  * Notification routing.
 217  *
 218  * Gets id and checks if there are notification request for it's idx
 219  * and val.  If there are such requests notify the listeners with the
 220  * given notify event.
 221  *
 222  */
 223 static void cn_notify(struct cb_id *id, u32 notify_event)
 224 {
 225         struct cn_ctl_entry *ent;
 226
 227         mutex_lock(&notify_lock);
 228         list_for_each_entry(ent, &notify_list, notify_entry) {
 229                 int i;
 230                 struct cn_notify_req *req;
 231                 struct cn_ctl_msg *ctl = ent->msg;
 232                 int idx_found, val_found;
 233
 234                 idx_found = val_found = 0;
 235
 236                 req = (struct cn_notify_req *)ctl->data;
 237                 for (i = 0; i < ctl->idx_notify_num; ++i, ++req) {
 238                         if (id->idx >= req->first &&
 239                                         id->idx < req->first + req->range) {
 240                                 idx_found = 1;
 241                                 break;
 242                         }
 243                 }
 244
 245                 for (i = 0; i < ctl->val_notify_num; ++i, ++req) {
 246                         if (id->val >= req->first &&
 247                                         id->val < req->first + req->range) {
 248                                 val_found = 1;
 249                                 break;
 250                         }
 251                 }
 252
 253                 if (idx_found && val_found) {
 254                         struct cn_msg m = { .ack = notify_event, };
 255
 256                         memcpy(&m.id, id, sizeof(m.id));
 257                         cn_netlink_send(&m, ctl->group, GFP_KERNEL);
 258                 }
 259         }
 260         mutex_unlock(&notify_lock);
 261 }
 262
 263 /*
 264  * Callback add routing - adds callback with given ID and name.
 265  * If there is registered callback with the same ID it will not be added.
 266  *
 267  * May sleep.
 268  */
 269 int cn_add_callback(struct cb_id *id, char *name, void (*callback)(void *))
 270 {
 271         int err;
 272         struct cn_dev *dev = &cdev;
 273
 274         if (!cn_already_initialized)
 275                 return -EAGAIN;
 276
 277         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
 278         if (err)
 279                 return err;
 280
 281         cn_notify(id, 0);
 282
 283         return 0;
 284 }
 285 EXPORT_SYMBOL_GPL(cn_add_callback);
 286
 287 /*
 288  * Callback remove routing - removes callback
 289  * with given ID.
 290  * If there is no registered callback with given
 291  * ID nothing happens.
 292  *
 293  * May sleep while waiting for reference counter to become zero.
 294  */
 295 void cn_del_callback(struct cb_id *id)
 296 {
 297         struct cn_dev *dev = &cdev;
 298
 299         cn_queue_del_callback(dev->cbdev, id);
 300         cn_notify(id, 1);
 301 }
 302 EXPORT_SYMBOL_GPL(cn_del_callback);
 303
 304 /*
 305  * Checks two connector's control messages to be the same.
 306  * Returns 1 if they are the same or if the first one is corrupted.
 307  */
 308 static int cn_ctl_msg_equals(struct cn_ctl_msg *m1, struct cn_ctl_msg *m2)
 309 {
 310         int i;
 311         struct cn_notify_req *req1, *req2;
 312
 313         if (m1->idx_notify_num != m2->idx_notify_num)
 314                 return 0;
 315
 316         if (m1->val_notify_num != m2->val_notify_num)
 317                 return 0;
 318
 319         if (m1->len != m2->len)
 320                 return 0;
 321
 322         if ((m1->idx_notify_num + m1->val_notify_num) * sizeof(*req1) !=
 323             m1->len)
 324                 return 1;
 325
 326         req1 = (struct cn_notify_req *)m1->data;
 327         req2 = (struct cn_notify_req *)m2->data;
 328
 329         for (i = 0; i < m1->idx_notify_num; ++i) {
 330                 if (req1->first != req2->first || req1->range != req2->range)
 331                         return 0;
 332                 req1++;
 333                 req2++;
 334         }
 335
 336         for (i = 0; i < m1->val_notify_num; ++i) {
 337                 if (req1->first != req2->first || req1->range != req2->range)
 338                         return 0;
 339                 req1++;
 340                 req2++;
 341         }
 342
 343         return 1;
 344 }
 345
 346 /*
 347  * Main connector device's callback.
 348  *
 349  * Used for notification of a request's processing.
 350  */
 351 static void cn_callback(void *data)
 352 {
 353         struct cn_msg *msg = data;
 354         struct cn_ctl_msg *ctl;
 355         struct cn_ctl_entry *ent;
 356         u32 size;
 357
 358         if (msg->len < sizeof(*ctl))
 359                 return;
 360
 361         ctl = (struct cn_ctl_msg *)msg->data;
 362
 363         size = (sizeof(*ctl) + ((ctl->idx_notify_num +
 364                                  ctl->val_notify_num) *
 365                                 sizeof(struct cn_notify_req)));
 366
 367         if (msg->len != size)
 368                 return;
 369
 370         if (ctl->len + sizeof(*ctl) != msg->len)
 371                 return;
 372
 373         /*
 374          * Remove notification.
 375          */
 376         if (ctl->group == 0) {
 377                 struct cn_ctl_entry *n;
 378
 379                 mutex_lock(&notify_lock);
 380                 list_for_each_entry_safe(ent, n, &notify_list, notify_entry) {
 381                         if (cn_ctl_msg_equals(ent->msg, ctl)) {
 382                                 list_del(&ent->notify_entry);
 383                                 kfree(ent);
 384                         }
 385                 }
 386                 mutex_unlock(&notify_lock);
 387
 388                 return;
 389         }
 390
 391         size += sizeof(*ent);
 392
 393         ent = kzalloc(size, GFP_KERNEL);
 394         if (!ent)
 395                 return;
 396
 397         ent->msg = (struct cn_ctl_msg *)(ent + 1);
 398
 399         memcpy(ent->msg, ctl, size - sizeof(*ent));
 400
 401         mutex_lock(&notify_lock);
 402         list_add(&ent->notify_entry, &notify_list);
 403         mutex_unlock(&notify_lock);
 404 }
 405
 406 static int __devinit cn_init(void)
 407 {
 408         struct cn_dev *dev = &cdev;
 409         int err;
 410
 411         dev->input = cn_rx_skb;
 412         dev->id.idx = cn_idx;
 413         dev->id.val = cn_val;
 414
 415         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,
 416                                          CN_NETLINK_USERS + 0xf,
 417                                          dev->input, NULL, THIS_MODULE);
 418         if (!dev->nls)
 419                 return -EIO;
 420
 421         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
 422         if (!dev->cbdev) {
 423                 netlink_kernel_release(dev->nls);
 424                 return -EINVAL;
 425         }
 426
 427         cn_already_initialized = 1;
 428
 429         err = cn_add_callback(&dev->id, "connector", &cn_callback);
 430         if (err) {
 431                 cn_already_initialized = 0;
 432                 cn_queue_free_dev(dev->cbdev);
 433                 netlink_kernel_release(dev->nls);
 434                 return -EINVAL;
 435         }
 436
 437         return 0;
 438 }
 439
 440 static void __devexit cn_fini(void)
 441 {
 442         struct cn_dev *dev = &cdev;
 443
 444         cn_already_initialized = 0;
 445
 446         cn_del_callback(&dev->id);
 447         cn_queue_free_dev(dev->cbdev);
 448         netlink_kernel_release(dev->nls);
 449 }
 450
 451 subsys_initcall(cn_init);
 452 module_exit(cn_fini);