connector: remove lazy workqueue creation
[linux-2.6.git] / drivers / connector / connector.c
1 /*
2  *      connector.c
3  *
4  * 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
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/slab.h>
30 #include <linux/mutex.h>
31 #include <linux/proc_fs.h>
32 #include <linux/spinlock.h>
33
34 #include <net/sock.h>
35
36 MODULE_LICENSE("GPL");
37 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
38 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
39
40 static struct cn_dev cdev;
41
42 static int cn_already_initialized;
43
44 /*
45  * msg->seq and msg->ack are used to determine message genealogy.
46  * When someone sends message it puts there locally unique sequence
47  * and random acknowledge numbers.  Sequence number may be copied into
48  * nlmsghdr->nlmsg_seq too.
49  *
50  * Sequence number is incremented with each message to be sent.
51  *
52  * If we expect reply to our message then the sequence number in
53  * received message MUST be the same as in original message, and
54  * acknowledge number MUST be the same + 1.
55  *
56  * If we receive a message and its sequence number is not equal to the
57  * one we are expecting then it is a new message.
58  *
59  * If we receive a message and its sequence number is the same as one
60  * we are expecting but it's acknowledgement number is not equal to
61  * the acknowledgement number in the original message + 1, then it is
62  * a new message.
63  *
64  */
65 int cn_netlink_send(struct cn_msg *msg, u32 __group, gfp_t gfp_mask)
66 {
67         struct cn_callback_entry *__cbq;
68         unsigned int size;
69         struct sk_buff *skb;
70         struct nlmsghdr *nlh;
71         struct cn_msg *data;
72         struct cn_dev *dev = &cdev;
73         u32 group = 0;
74         int found = 0;
75
76         if (!__group) {
77                 spin_lock_bh(&dev->cbdev->queue_lock);
78                 list_for_each_entry(__cbq, &dev->cbdev->queue_list,
79                                     callback_entry) {
80                         if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
81                                 found = 1;
82                                 group = __cbq->group;
83                                 break;
84                         }
85                 }
86                 spin_unlock_bh(&dev->cbdev->queue_lock);
87
88                 if (!found)
89                         return -ENODEV;
90         } else {
91                 group = __group;
92         }
93
94         if (!netlink_has_listeners(dev->nls, group))
95                 return -ESRCH;
96
97         size = NLMSG_SPACE(sizeof(*msg) + msg->len);
98
99         skb = alloc_skb(size, gfp_mask);
100         if (!skb)
101                 return -ENOMEM;
102
103         nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
104
105         data = NLMSG_DATA(nlh);
106
107         memcpy(data, msg, sizeof(*data) + msg->len);
108
109         NETLINK_CB(skb).dst_group = group;
110
111         return netlink_broadcast(dev->nls, skb, 0, group, gfp_mask);
112
113 nlmsg_failure:
114         kfree_skb(skb);
115         return -EINVAL;
116 }
117 EXPORT_SYMBOL_GPL(cn_netlink_send);
118
119 /*
120  * Callback helper - queues work and setup destructor for given data.
121  */
122 static int cn_call_callback(struct sk_buff *skb)
123 {
124         struct cn_callback_entry *__cbq, *__new_cbq;
125         struct cn_dev *dev = &cdev;
126         struct cn_msg *msg = NLMSG_DATA(nlmsg_hdr(skb));
127         int err = -ENODEV;
128
129         spin_lock_bh(&dev->cbdev->queue_lock);
130         list_for_each_entry(__cbq, &dev->cbdev->queue_list, callback_entry) {
131                 if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
132                         if (likely(!work_pending(&__cbq->work) &&
133                                         __cbq->data.skb == NULL)) {
134                                 __cbq->data.skb = skb;
135
136                                 if (queue_work(dev->cbdev->cn_queue,
137                                                &__cbq->work))
138                                         err = 0;
139                                 else
140                                         err = -EINVAL;
141                         } else {
142                                 struct cn_callback_data *d;
143
144                                 err = -ENOMEM;
145                                 __new_cbq = kzalloc(sizeof(struct cn_callback_entry), GFP_ATOMIC);
146                                 if (__new_cbq) {
147                                         d = &__new_cbq->data;
148                                         d->skb = skb;
149                                         d->callback = __cbq->data.callback;
150                                         d->free = __new_cbq;
151
152                                         INIT_WORK(&__new_cbq->work,
153                                                         &cn_queue_wrapper);
154
155                                         if (queue_work(dev->cbdev->cn_queue,
156                                                        &__new_cbq->work))
157                                                 err = 0;
158                                         else {
159                                                 kfree(__new_cbq);
160                                                 err = -EINVAL;
161                                         }
162                                 }
163                         }
164                         break;
165                 }
166         }
167         spin_unlock_bh(&dev->cbdev->queue_lock);
168
169         return err;
170 }
171
172 /*
173  * Main netlink receiving function.
174  *
175  * It checks skb, netlink header and msg sizes, and calls callback helper.
176  */
177 static void cn_rx_skb(struct sk_buff *__skb)
178 {
179         struct nlmsghdr *nlh;
180         int err;
181         struct sk_buff *skb;
182
183         skb = skb_get(__skb);
184
185         if (skb->len >= NLMSG_SPACE(0)) {
186                 nlh = nlmsg_hdr(skb);
187
188                 if (nlh->nlmsg_len < sizeof(struct cn_msg) ||
189                     skb->len < nlh->nlmsg_len ||
190                     nlh->nlmsg_len > CONNECTOR_MAX_MSG_SIZE) {
191                         kfree_skb(skb);
192                         return;
193                 }
194
195                 err = cn_call_callback(skb);
196                 if (err < 0)
197                         kfree_skb(skb);
198         }
199 }
200
201 /*
202  * Callback add routing - adds callback with given ID and name.
203  * If there is registered callback with the same ID it will not be added.
204  *
205  * May sleep.
206  */
207 int cn_add_callback(struct cb_id *id, char *name,
208                     void (*callback)(struct cn_msg *, struct netlink_skb_parms *))
209 {
210         int err;
211         struct cn_dev *dev = &cdev;
212
213         if (!cn_already_initialized)
214                 return -EAGAIN;
215
216         err = cn_queue_add_callback(dev->cbdev, name, id, callback);
217         if (err)
218                 return err;
219
220         return 0;
221 }
222 EXPORT_SYMBOL_GPL(cn_add_callback);
223
224 /*
225  * Callback remove routing - removes callback
226  * with given ID.
227  * If there is no registered callback with given
228  * ID nothing happens.
229  *
230  * May sleep while waiting for reference counter to become zero.
231  */
232 void cn_del_callback(struct cb_id *id)
233 {
234         struct cn_dev *dev = &cdev;
235
236         cn_queue_del_callback(dev->cbdev, id);
237 }
238 EXPORT_SYMBOL_GPL(cn_del_callback);
239
240 static int cn_proc_show(struct seq_file *m, void *v)
241 {
242         struct cn_queue_dev *dev = cdev.cbdev;
243         struct cn_callback_entry *cbq;
244
245         seq_printf(m, "Name            ID\n");
246
247         spin_lock_bh(&dev->queue_lock);
248
249         list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
250                 seq_printf(m, "%-15s %u:%u\n",
251                            cbq->id.name,
252                            cbq->id.id.idx,
253                            cbq->id.id.val);
254         }
255
256         spin_unlock_bh(&dev->queue_lock);
257
258         return 0;
259 }
260
261 static int cn_proc_open(struct inode *inode, struct file *file)
262 {
263         return single_open(file, cn_proc_show, NULL);
264 }
265
266 static const struct file_operations cn_file_ops = {
267         .owner   = THIS_MODULE,
268         .open    = cn_proc_open,
269         .read    = seq_read,
270         .llseek  = seq_lseek,
271         .release = single_release
272 };
273
274 static int __devinit cn_init(void)
275 {
276         struct cn_dev *dev = &cdev;
277
278         dev->input = cn_rx_skb;
279
280         dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR,
281                                          CN_NETLINK_USERS + 0xf,
282                                          dev->input, NULL, THIS_MODULE);
283         if (!dev->nls)
284                 return -EIO;
285
286         dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
287         if (!dev->cbdev) {
288                 netlink_kernel_release(dev->nls);
289                 return -EINVAL;
290         }
291
292         cn_already_initialized = 1;
293
294         proc_net_fops_create(&init_net, "connector", S_IRUGO, &cn_file_ops);
295
296         return 0;
297 }
298
299 static void __devexit cn_fini(void)
300 {
301         struct cn_dev *dev = &cdev;
302
303         cn_already_initialized = 0;
304
305         proc_net_remove(&init_net, "connector");
306
307         cn_queue_free_dev(dev->cbdev);
308         netlink_kernel_release(dev->nls);
309 }
310
311 subsys_initcall(cn_init);
312 module_exit(cn_fini);