xref: /openbmc/linux/drivers/connector/connector.c (revision f42b3800) 
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);
453