Merge branch 'release' of master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6
[linux-2.6] / drivers / w1 / w1.c
1 /*
2  *      w1.c
3  *
4  * Copyright (c) 2004 Evgeniy Polyakov <johnpol@2ka.mipt.ru>
5  *
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/delay.h>
23 #include <linux/kernel.h>
24 #include <linux/module.h>
25 #include <linux/moduleparam.h>
26 #include <linux/list.h>
27 #include <linux/interrupt.h>
28 #include <linux/spinlock.h>
29 #include <linux/timer.h>
30 #include <linux/device.h>
31 #include <linux/slab.h>
32 #include <linux/sched.h>
33 #include <linux/kthread.h>
34 #include <linux/freezer.h>
35
36 #include <asm/atomic.h>
37
38 #include "w1.h"
39 #include "w1_log.h"
40 #include "w1_int.h"
41 #include "w1_family.h"
42 #include "w1_netlink.h"
43
44 MODULE_LICENSE("GPL");
45 MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
46 MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol.");
47
48 static int w1_timeout = 10;
49 static int w1_control_timeout = 1;
50 int w1_max_slave_count = 10;
51 int w1_max_slave_ttl = 10;
52
53 module_param_named(timeout, w1_timeout, int, 0);
54 module_param_named(control_timeout, w1_control_timeout, int, 0);
55 module_param_named(max_slave_count, w1_max_slave_count, int, 0);
56 module_param_named(slave_ttl, w1_max_slave_ttl, int, 0);
57
58 DEFINE_MUTEX(w1_mlock);
59 LIST_HEAD(w1_masters);
60
61 static struct task_struct *w1_control_thread;
62
63 static int w1_master_match(struct device *dev, struct device_driver *drv)
64 {
65         return 1;
66 }
67
68 static int w1_master_probe(struct device *dev)
69 {
70         return -ENODEV;
71 }
72
73 static void w1_master_release(struct device *dev)
74 {
75         struct w1_master *md = dev_to_w1_master(dev);
76
77         dev_dbg(dev, "%s: Releasing %s.\n", __func__, md->name);
78         memset(md, 0, sizeof(struct w1_master) + sizeof(struct w1_bus_master));
79         kfree(md);
80 }
81
82 static void w1_slave_release(struct device *dev)
83 {
84         struct w1_slave *sl = dev_to_w1_slave(dev);
85
86         printk("%s: Releasing %s.\n", __func__, sl->name);
87
88         while (atomic_read(&sl->refcnt)) {
89                 printk("Waiting for %s to become free: refcnt=%d.\n",
90                                 sl->name, atomic_read(&sl->refcnt));
91                 if (msleep_interruptible(1000))
92                         flush_signals(current);
93         }
94
95         w1_family_put(sl->family);
96         sl->master->slave_count--;
97
98         complete(&sl->released);
99 }
100
101 static ssize_t w1_slave_read_name(struct device *dev, struct device_attribute *attr, char *buf)
102 {
103         struct w1_slave *sl = dev_to_w1_slave(dev);
104
105         return sprintf(buf, "%s\n", sl->name);
106 }
107
108 static ssize_t w1_slave_read_id(struct kobject *kobj, char *buf, loff_t off, size_t count)
109 {
110         struct w1_slave *sl = kobj_to_w1_slave(kobj);
111
112         if (off > 8) {
113                 count = 0;
114         } else {
115                 if (off + count > 8)
116                         count = 8 - off;
117
118                 memcpy(buf, (u8 *)&sl->reg_num, count);
119         }
120
121         return count;
122 }
123
124 static struct device_attribute w1_slave_attr_name =
125         __ATTR(name, S_IRUGO, w1_slave_read_name, NULL);
126
127 static struct bin_attribute w1_slave_attr_bin_id = {
128       .attr = {
129               .name = "id",
130               .mode = S_IRUGO,
131               .owner = THIS_MODULE,
132       },
133       .size = 8,
134       .read = w1_slave_read_id,
135 };
136
137 /* Default family */
138
139 static ssize_t w1_default_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
140 {
141         struct w1_slave *sl = kobj_to_w1_slave(kobj);
142
143         mutex_lock(&sl->master->mutex);
144         if (w1_reset_select_slave(sl)) {
145                 count = 0;
146                 goto out_up;
147         }
148
149         w1_write_block(sl->master, buf, count);
150
151 out_up:
152         mutex_unlock(&sl->master->mutex);
153         return count;
154 }
155
156 static ssize_t w1_default_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
157 {
158         struct w1_slave *sl = kobj_to_w1_slave(kobj);
159
160         mutex_lock(&sl->master->mutex);
161         w1_read_block(sl->master, buf, count);
162         mutex_unlock(&sl->master->mutex);
163         return count;
164 }
165
166 static struct bin_attribute w1_default_attr = {
167       .attr = {
168               .name = "rw",
169               .mode = S_IRUGO | S_IWUSR,
170               .owner = THIS_MODULE,
171       },
172       .size = PAGE_SIZE,
173       .read = w1_default_read,
174       .write = w1_default_write,
175 };
176
177 static int w1_default_add_slave(struct w1_slave *sl)
178 {
179         return sysfs_create_bin_file(&sl->dev.kobj, &w1_default_attr);
180 }
181
182 static void w1_default_remove_slave(struct w1_slave *sl)
183 {
184         sysfs_remove_bin_file(&sl->dev.kobj, &w1_default_attr);
185 }
186
187 static struct w1_family_ops w1_default_fops = {
188         .add_slave      = w1_default_add_slave,
189         .remove_slave   = w1_default_remove_slave,
190 };
191
192 static struct w1_family w1_default_family = {
193         .fops = &w1_default_fops,
194 };
195
196 static int w1_uevent(struct device *dev, char **envp, int num_envp, char *buffer, int buffer_size);
197
198 static struct bus_type w1_bus_type = {
199         .name = "w1",
200         .match = w1_master_match,
201         .uevent = w1_uevent,
202 };
203
204 struct device_driver w1_master_driver = {
205         .name = "w1_master_driver",
206         .bus = &w1_bus_type,
207         .probe = w1_master_probe,
208 };
209
210 struct device w1_master_device = {
211         .parent = NULL,
212         .bus = &w1_bus_type,
213         .bus_id = "w1 bus master",
214         .driver = &w1_master_driver,
215         .release = &w1_master_release
216 };
217
218 static struct device_driver w1_slave_driver = {
219         .name = "w1_slave_driver",
220         .bus = &w1_bus_type,
221 };
222
223 #if 0
224 struct device w1_slave_device = {
225         .parent = NULL,
226         .bus = &w1_bus_type,
227         .bus_id = "w1 bus slave",
228         .driver = &w1_slave_driver,
229         .release = &w1_slave_release
230 };
231 #endif  /*  0  */
232
233 static ssize_t w1_master_attribute_show_name(struct device *dev, struct device_attribute *attr, char *buf)
234 {
235         struct w1_master *md = dev_to_w1_master(dev);
236         ssize_t count;
237
238         mutex_lock(&md->mutex);
239         count = sprintf(buf, "%s\n", md->name);
240         mutex_unlock(&md->mutex);
241
242         return count;
243 }
244
245 static ssize_t w1_master_attribute_store_search(struct device * dev,
246                                                 struct device_attribute *attr,
247                                                 const char * buf, size_t count)
248 {
249         struct w1_master *md = dev_to_w1_master(dev);
250
251         mutex_lock(&md->mutex);
252         md->search_count = simple_strtol(buf, NULL, 0);
253         mutex_unlock(&md->mutex);
254
255         return count;
256 }
257
258 static ssize_t w1_master_attribute_show_search(struct device *dev,
259                                                struct device_attribute *attr,
260                                                char *buf)
261 {
262         struct w1_master *md = dev_to_w1_master(dev);
263         ssize_t count;
264
265         mutex_lock(&md->mutex);
266         count = sprintf(buf, "%d\n", md->search_count);
267         mutex_unlock(&md->mutex);
268
269         return count;
270 }
271
272 static ssize_t w1_master_attribute_show_pointer(struct device *dev, struct device_attribute *attr, char *buf)
273 {
274         struct w1_master *md = dev_to_w1_master(dev);
275         ssize_t count;
276
277         mutex_lock(&md->mutex);
278         count = sprintf(buf, "0x%p\n", md->bus_master);
279         mutex_unlock(&md->mutex);
280         return count;
281 }
282
283 static ssize_t w1_master_attribute_show_timeout(struct device *dev, struct device_attribute *attr, char *buf)
284 {
285         ssize_t count;
286         count = sprintf(buf, "%d\n", w1_timeout);
287         return count;
288 }
289
290 static ssize_t w1_master_attribute_show_max_slave_count(struct device *dev, struct device_attribute *attr, char *buf)
291 {
292         struct w1_master *md = dev_to_w1_master(dev);
293         ssize_t count;
294
295         mutex_lock(&md->mutex);
296         count = sprintf(buf, "%d\n", md->max_slave_count);
297         mutex_unlock(&md->mutex);
298         return count;
299 }
300
301 static ssize_t w1_master_attribute_show_attempts(struct device *dev, struct device_attribute *attr, char *buf)
302 {
303         struct w1_master *md = dev_to_w1_master(dev);
304         ssize_t count;
305
306         mutex_lock(&md->mutex);
307         count = sprintf(buf, "%lu\n", md->attempts);
308         mutex_unlock(&md->mutex);
309         return count;
310 }
311
312 static ssize_t w1_master_attribute_show_slave_count(struct device *dev, struct device_attribute *attr, char *buf)
313 {
314         struct w1_master *md = dev_to_w1_master(dev);
315         ssize_t count;
316
317         mutex_lock(&md->mutex);
318         count = sprintf(buf, "%d\n", md->slave_count);
319         mutex_unlock(&md->mutex);
320         return count;
321 }
322
323 static ssize_t w1_master_attribute_show_slaves(struct device *dev, struct device_attribute *attr, char *buf)
324 {
325         struct w1_master *md = dev_to_w1_master(dev);
326         int c = PAGE_SIZE;
327
328         mutex_lock(&md->mutex);
329
330         if (md->slave_count == 0)
331                 c -= snprintf(buf + PAGE_SIZE - c, c, "not found.\n");
332         else {
333                 struct list_head *ent, *n;
334                 struct w1_slave *sl;
335
336                 list_for_each_safe(ent, n, &md->slist) {
337                         sl = list_entry(ent, struct w1_slave, w1_slave_entry);
338
339                         c -= snprintf(buf + PAGE_SIZE - c, c, "%s\n", sl->name);
340                 }
341         }
342
343         mutex_unlock(&md->mutex);
344
345         return PAGE_SIZE - c;
346 }
347
348 #define W1_MASTER_ATTR_RO(_name, _mode)                         \
349         struct device_attribute w1_master_attribute_##_name =   \
350                 __ATTR(w1_master_##_name, _mode,                \
351                        w1_master_attribute_show_##_name, NULL)
352
353 #define W1_MASTER_ATTR_RW(_name, _mode)                         \
354         struct device_attribute w1_master_attribute_##_name =   \
355                 __ATTR(w1_master_##_name, _mode,                \
356                        w1_master_attribute_show_##_name,        \
357                        w1_master_attribute_store_##_name)
358
359 static W1_MASTER_ATTR_RO(name, S_IRUGO);
360 static W1_MASTER_ATTR_RO(slaves, S_IRUGO);
361 static W1_MASTER_ATTR_RO(slave_count, S_IRUGO);
362 static W1_MASTER_ATTR_RO(max_slave_count, S_IRUGO);
363 static W1_MASTER_ATTR_RO(attempts, S_IRUGO);
364 static W1_MASTER_ATTR_RO(timeout, S_IRUGO);
365 static W1_MASTER_ATTR_RO(pointer, S_IRUGO);
366 static W1_MASTER_ATTR_RW(search, S_IRUGO | S_IWUGO);
367
368 static struct attribute *w1_master_default_attrs[] = {
369         &w1_master_attribute_name.attr,
370         &w1_master_attribute_slaves.attr,
371         &w1_master_attribute_slave_count.attr,
372         &w1_master_attribute_max_slave_count.attr,
373         &w1_master_attribute_attempts.attr,
374         &w1_master_attribute_timeout.attr,
375         &w1_master_attribute_pointer.attr,
376         &w1_master_attribute_search.attr,
377         NULL
378 };
379
380 static struct attribute_group w1_master_defattr_group = {
381         .attrs = w1_master_default_attrs,
382 };
383
384 int w1_create_master_attributes(struct w1_master *master)
385 {
386         return sysfs_create_group(&master->dev.kobj, &w1_master_defattr_group);
387 }
388
389 static void w1_destroy_master_attributes(struct w1_master *master)
390 {
391         sysfs_remove_group(&master->dev.kobj, &w1_master_defattr_group);
392 }
393
394 #ifdef CONFIG_HOTPLUG
395 static int w1_uevent(struct device *dev, char **envp, int num_envp,
396                         char *buffer, int buffer_size)
397 {
398         struct w1_master *md = NULL;
399         struct w1_slave *sl = NULL;
400         char *event_owner, *name;
401         int err, cur_index=0, cur_len=0;
402
403         if (dev->driver == &w1_master_driver) {
404                 md = container_of(dev, struct w1_master, dev);
405                 event_owner = "master";
406                 name = md->name;
407         } else if (dev->driver == &w1_slave_driver) {
408                 sl = container_of(dev, struct w1_slave, dev);
409                 event_owner = "slave";
410                 name = sl->name;
411         } else {
412                 dev_dbg(dev, "Unknown event.\n");
413                 return -EINVAL;
414         }
415
416         dev_dbg(dev, "Hotplug event for %s %s, bus_id=%s.\n",
417                         event_owner, name, dev->bus_id);
418
419         if (dev->driver != &w1_slave_driver || !sl)
420                 return 0;
421
422         err = add_uevent_var(envp, num_envp, &cur_index, buffer, buffer_size,
423                         &cur_len, "W1_FID=%02X", sl->reg_num.family);
424         if (err)
425                 return err;
426
427         err = add_uevent_var(envp, num_envp, &cur_index, buffer, buffer_size,
428                         &cur_len, "W1_SLAVE_ID=%024LX",
429                         (unsigned long long)sl->reg_num.id);
430         if (err)
431                 return err;
432
433         return 0;
434 };
435 #else
436 static int w1_uevent(struct device *dev, char **envp, int num_envp,
437                         char *buffer, int buffer_size)
438 {
439         return 0;
440 }
441 #endif
442
443 static int __w1_attach_slave_device(struct w1_slave *sl)
444 {
445         int err;
446
447         sl->dev.parent = &sl->master->dev;
448         sl->dev.driver = &w1_slave_driver;
449         sl->dev.bus = &w1_bus_type;
450         sl->dev.release = &w1_slave_release;
451
452         snprintf(&sl->dev.bus_id[0], sizeof(sl->dev.bus_id),
453                  "%02x-%012llx",
454                  (unsigned int) sl->reg_num.family,
455                  (unsigned long long) sl->reg_num.id);
456         snprintf(&sl->name[0], sizeof(sl->name),
457                  "%02x-%012llx",
458                  (unsigned int) sl->reg_num.family,
459                  (unsigned long long) sl->reg_num.id);
460
461         dev_dbg(&sl->dev, "%s: registering %s as %p.\n", __func__,
462                 &sl->dev.bus_id[0]);
463
464         err = device_register(&sl->dev);
465         if (err < 0) {
466                 dev_err(&sl->dev,
467                         "Device registration [%s] failed. err=%d\n",
468                         sl->dev.bus_id, err);
469                 return err;
470         }
471
472         /* Create "name" entry */
473         err = device_create_file(&sl->dev, &w1_slave_attr_name);
474         if (err < 0) {
475                 dev_err(&sl->dev,
476                         "sysfs file creation for [%s] failed. err=%d\n",
477                         sl->dev.bus_id, err);
478                 goto out_unreg;
479         }
480
481         /* Create "id" entry */
482         err = sysfs_create_bin_file(&sl->dev.kobj, &w1_slave_attr_bin_id);
483         if (err < 0) {
484                 dev_err(&sl->dev,
485                         "sysfs file creation for [%s] failed. err=%d\n",
486                         sl->dev.bus_id, err);
487                 goto out_rem1;
488         }
489
490         /* if the family driver needs to initialize something... */
491         if (sl->family->fops && sl->family->fops->add_slave &&
492             ((err = sl->family->fops->add_slave(sl)) < 0)) {
493                 dev_err(&sl->dev,
494                         "sysfs file creation for [%s] failed. err=%d\n",
495                         sl->dev.bus_id, err);
496                 goto out_rem2;
497         }
498
499         list_add_tail(&sl->w1_slave_entry, &sl->master->slist);
500
501         return 0;
502
503 out_rem2:
504         sysfs_remove_bin_file(&sl->dev.kobj, &w1_slave_attr_bin_id);
505 out_rem1:
506         device_remove_file(&sl->dev, &w1_slave_attr_name);
507 out_unreg:
508         device_unregister(&sl->dev);
509         return err;
510 }
511
512 static int w1_attach_slave_device(struct w1_master *dev, struct w1_reg_num *rn)
513 {
514         struct w1_slave *sl;
515         struct w1_family *f;
516         int err;
517         struct w1_netlink_msg msg;
518
519         sl = kmalloc(sizeof(struct w1_slave), GFP_KERNEL);
520         if (!sl) {
521                 dev_err(&dev->dev,
522                          "%s: failed to allocate new slave device.\n",
523                          __func__);
524                 return -ENOMEM;
525         }
526
527         memset(sl, 0, sizeof(*sl));
528
529         sl->owner = THIS_MODULE;
530         sl->master = dev;
531         set_bit(W1_SLAVE_ACTIVE, (long *)&sl->flags);
532
533         memset(&msg, 0, sizeof(msg));
534         memcpy(&sl->reg_num, rn, sizeof(sl->reg_num));
535         atomic_set(&sl->refcnt, 0);
536         init_completion(&sl->released);
537
538         spin_lock(&w1_flock);
539         f = w1_family_registered(rn->family);
540         if (!f) {
541                 f= &w1_default_family;
542                 dev_info(&dev->dev, "Family %x for %02x.%012llx.%02x is not registered.\n",
543                           rn->family, rn->family,
544                           (unsigned long long)rn->id, rn->crc);
545         }
546         __w1_family_get(f);
547         spin_unlock(&w1_flock);
548
549         sl->family = f;
550
551
552         err = __w1_attach_slave_device(sl);
553         if (err < 0) {
554                 dev_err(&dev->dev, "%s: Attaching %s failed.\n", __func__,
555                          sl->name);
556                 w1_family_put(sl->family);
557                 kfree(sl);
558                 return err;
559         }
560
561         sl->ttl = dev->slave_ttl;
562         dev->slave_count++;
563
564         memcpy(msg.id.id, rn, sizeof(msg.id));
565         msg.type = W1_SLAVE_ADD;
566         w1_netlink_send(dev, &msg);
567
568         return 0;
569 }
570
571 static void w1_slave_detach(struct w1_slave *sl)
572 {
573         struct w1_netlink_msg msg;
574
575         dev_dbg(&sl->dev, "%s: detaching %s [%p].\n", __func__, sl->name, sl);
576
577         list_del(&sl->w1_slave_entry);
578
579         if (sl->family->fops && sl->family->fops->remove_slave)
580                 sl->family->fops->remove_slave(sl);
581
582         memset(&msg, 0, sizeof(msg));
583         memcpy(msg.id.id, &sl->reg_num, sizeof(msg.id));
584         msg.type = W1_SLAVE_REMOVE;
585         w1_netlink_send(sl->master, &msg);
586
587         sysfs_remove_bin_file(&sl->dev.kobj, &w1_slave_attr_bin_id);
588         device_remove_file(&sl->dev, &w1_slave_attr_name);
589         device_unregister(&sl->dev);
590
591         wait_for_completion(&sl->released);
592         kfree(sl);
593 }
594
595 static struct w1_master *w1_search_master(void *data)
596 {
597         struct w1_master *dev;
598         int found = 0;
599
600         mutex_lock(&w1_mlock);
601         list_for_each_entry(dev, &w1_masters, w1_master_entry) {
602                 if (dev->bus_master->data == data) {
603                         found = 1;
604                         atomic_inc(&dev->refcnt);
605                         break;
606                 }
607         }
608         mutex_unlock(&w1_mlock);
609
610         return (found)?dev:NULL;
611 }
612
613 struct w1_master *w1_search_master_id(u32 id)
614 {
615         struct w1_master *dev;
616         int found = 0;
617
618         mutex_lock(&w1_mlock);
619         list_for_each_entry(dev, &w1_masters, w1_master_entry) {
620                 if (dev->id == id) {
621                         found = 1;
622                         atomic_inc(&dev->refcnt);
623                         break;
624                 }
625         }
626         mutex_unlock(&w1_mlock);
627
628         return (found)?dev:NULL;
629 }
630
631 struct w1_slave *w1_search_slave(struct w1_reg_num *id)
632 {
633         struct w1_master *dev;
634         struct w1_slave *sl = NULL;
635         int found = 0;
636
637         mutex_lock(&w1_mlock);
638         list_for_each_entry(dev, &w1_masters, w1_master_entry) {
639                 mutex_lock(&dev->mutex);
640                 list_for_each_entry(sl, &dev->slist, w1_slave_entry) {
641                         if (sl->reg_num.family == id->family &&
642                                         sl->reg_num.id == id->id &&
643                                         sl->reg_num.crc == id->crc) {
644                                 found = 1;
645                                 atomic_inc(&dev->refcnt);
646                                 atomic_inc(&sl->refcnt);
647                                 break;
648                         }
649                 }
650                 mutex_unlock(&dev->mutex);
651
652                 if (found)
653                         break;
654         }
655         mutex_unlock(&w1_mlock);
656
657         return (found)?sl:NULL;
658 }
659
660 void w1_reconnect_slaves(struct w1_family *f)
661 {
662         struct w1_master *dev;
663
664         mutex_lock(&w1_mlock);
665         list_for_each_entry(dev, &w1_masters, w1_master_entry) {
666                 dev_dbg(&dev->dev, "Reconnecting slaves in %s into new family %02x.\n",
667                                 dev->name, f->fid);
668                 set_bit(W1_MASTER_NEED_RECONNECT, &dev->flags);
669         }
670         mutex_unlock(&w1_mlock);
671 }
672
673 static void w1_slave_found(void *data, u64 rn)
674 {
675         int slave_count;
676         struct w1_slave *sl;
677         struct list_head *ent;
678         struct w1_reg_num *tmp;
679         int family_found = 0;
680         struct w1_master *dev;
681         u64 rn_le = cpu_to_le64(rn);
682
683         dev = w1_search_master(data);
684         if (!dev) {
685                 printk(KERN_ERR "Failed to find w1 master device for data %p, "
686                        "it is impossible.\n", data);
687                 return;
688         }
689
690         tmp = (struct w1_reg_num *) &rn;
691
692         slave_count = 0;
693         list_for_each(ent, &dev->slist) {
694
695                 sl = list_entry(ent, struct w1_slave, w1_slave_entry);
696
697                 if (sl->reg_num.family == tmp->family &&
698                     sl->reg_num.id == tmp->id &&
699                     sl->reg_num.crc == tmp->crc) {
700                         set_bit(W1_SLAVE_ACTIVE, (long *)&sl->flags);
701                         break;
702                 } else if (sl->reg_num.family == tmp->family) {
703                         family_found = 1;
704                         break;
705                 }
706
707                 slave_count++;
708         }
709
710         if (slave_count == dev->slave_count &&
711                 rn && ((rn >> 56) & 0xff) == w1_calc_crc8((u8 *)&rn_le, 7)) {
712                 w1_attach_slave_device(dev, tmp);
713         }
714
715         atomic_dec(&dev->refcnt);
716 }
717
718 /**
719  * Performs a ROM Search & registers any devices found.
720  * The 1-wire search is a simple binary tree search.
721  * For each bit of the address, we read two bits and write one bit.
722  * The bit written will put to sleep all devies that don't match that bit.
723  * When the two reads differ, the direction choice is obvious.
724  * When both bits are 0, we must choose a path to take.
725  * When we can scan all 64 bits without having to choose a path, we are done.
726  *
727  * See "Application note 187 1-wire search algorithm" at www.maxim-ic.com
728  *
729  * @dev        The master device to search
730  * @cb         Function to call when a device is found
731  */
732 void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb)
733 {
734         u64 last_rn, rn, tmp64;
735         int i, slave_count = 0;
736         int last_zero, last_device;
737         int search_bit, desc_bit;
738         u8  triplet_ret = 0;
739
740         search_bit = 0;
741         rn = last_rn = 0;
742         last_device = 0;
743         last_zero = -1;
744
745         desc_bit = 64;
746
747         while ( !last_device && (slave_count++ < dev->max_slave_count) ) {
748                 last_rn = rn;
749                 rn = 0;
750
751                 /*
752                  * Reset bus and all 1-wire device state machines
753                  * so they can respond to our requests.
754                  *
755                  * Return 0 - device(s) present, 1 - no devices present.
756                  */
757                 if (w1_reset_bus(dev)) {
758                         dev_dbg(&dev->dev, "No devices present on the wire.\n");
759                         break;
760                 }
761
762                 /* Start the search */
763                 w1_write_8(dev, search_type);
764                 for (i = 0; i < 64; ++i) {
765                         /* Determine the direction/search bit */
766                         if (i == desc_bit)
767                                 search_bit = 1;   /* took the 0 path last time, so take the 1 path */
768                         else if (i > desc_bit)
769                                 search_bit = 0;   /* take the 0 path on the next branch */
770                         else
771                                 search_bit = ((last_rn >> i) & 0x1);
772
773                         /** Read two bits and write one bit */
774                         triplet_ret = w1_triplet(dev, search_bit);
775
776                         /* quit if no device responded */
777                         if ( (triplet_ret & 0x03) == 0x03 )
778                                 break;
779
780                         /* If both directions were valid, and we took the 0 path... */
781                         if (triplet_ret == 0)
782                                 last_zero = i;
783
784                         /* extract the direction taken & update the device number */
785                         tmp64 = (triplet_ret >> 2);
786                         rn |= (tmp64 << i);
787                 }
788
789                 if ( (triplet_ret & 0x03) != 0x03 ) {
790                         if ( (desc_bit == last_zero) || (last_zero < 0))
791                                 last_device = 1;
792                         desc_bit = last_zero;
793                         cb(dev->bus_master->data, rn);
794                 }
795         }
796 }
797
798 static int w1_control(void *data)
799 {
800         struct w1_slave *sl, *sln;
801         struct w1_master *dev, *n;
802         int have_to_wait = 0;
803
804         while (!kthread_should_stop() || have_to_wait) {
805                 have_to_wait = 0;
806
807                 try_to_freeze();
808                 msleep_interruptible(w1_control_timeout * 1000);
809
810                 list_for_each_entry_safe(dev, n, &w1_masters, w1_master_entry) {
811                         if (!kthread_should_stop() && !dev->flags)
812                                 continue;
813                         /*
814                          * Little race: we can create thread but not set the flag.
815                          * Get a chance for external process to set flag up.
816                          */
817                         if (!dev->initialized) {
818                                 have_to_wait = 1;
819                                 continue;
820                         }
821
822                         if (kthread_should_stop() || test_bit(W1_MASTER_NEED_EXIT, &dev->flags)) {
823                                 set_bit(W1_MASTER_NEED_EXIT, &dev->flags);
824
825                                 mutex_lock(&w1_mlock);
826                                 list_del(&dev->w1_master_entry);
827                                 mutex_unlock(&w1_mlock);
828
829                                 mutex_lock(&dev->mutex);
830                                 list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
831                                         w1_slave_detach(sl);
832                                 }
833                                 w1_destroy_master_attributes(dev);
834                                 mutex_unlock(&dev->mutex);
835                                 atomic_dec(&dev->refcnt);
836                                 continue;
837                         }
838
839                         if (test_bit(W1_MASTER_NEED_RECONNECT, &dev->flags)) {
840                                 dev_dbg(&dev->dev, "Reconnecting slaves in device %s.\n", dev->name);
841                                 mutex_lock(&dev->mutex);
842                                 list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
843                                         if (sl->family->fid == W1_FAMILY_DEFAULT) {
844                                                 struct w1_reg_num rn;
845
846                                                 memcpy(&rn, &sl->reg_num, sizeof(rn));
847                                                 w1_slave_detach(sl);
848
849                                                 w1_attach_slave_device(dev, &rn);
850                                         }
851                                 }
852                                 dev_dbg(&dev->dev, "Reconnecting slaves in device %s has been finished.\n", dev->name);
853                                 clear_bit(W1_MASTER_NEED_RECONNECT, &dev->flags);
854                                 mutex_unlock(&dev->mutex);
855                         }
856                 }
857         }
858
859         return 0;
860 }
861
862 void w1_search_process(struct w1_master *dev, u8 search_type)
863 {
864         struct w1_slave *sl, *sln;
865
866         list_for_each_entry(sl, &dev->slist, w1_slave_entry)
867                 clear_bit(W1_SLAVE_ACTIVE, (long *)&sl->flags);
868
869         w1_search_devices(dev, search_type, w1_slave_found);
870
871         list_for_each_entry_safe(sl, sln, &dev->slist, w1_slave_entry) {
872                 if (!test_bit(W1_SLAVE_ACTIVE, (unsigned long *)&sl->flags) && !--sl->ttl) {
873                         w1_slave_detach(sl);
874
875                         dev->slave_count--;
876                 } else if (test_bit(W1_SLAVE_ACTIVE, (unsigned long *)&sl->flags))
877                         sl->ttl = dev->slave_ttl;
878         }
879
880         if (dev->search_count > 0)
881                 dev->search_count--;
882 }
883
884 int w1_process(void *data)
885 {
886         struct w1_master *dev = (struct w1_master *) data;
887
888         while (!kthread_should_stop() && !test_bit(W1_MASTER_NEED_EXIT, &dev->flags)) {
889                 try_to_freeze();
890                 msleep_interruptible(w1_timeout * 1000);
891
892                 if (kthread_should_stop() || test_bit(W1_MASTER_NEED_EXIT, &dev->flags))
893                         break;
894
895                 if (!dev->initialized)
896                         continue;
897
898                 if (dev->search_count == 0)
899                         continue;
900
901                 mutex_lock(&dev->mutex);
902                 w1_search_process(dev, W1_SEARCH);
903                 mutex_unlock(&dev->mutex);
904         }
905
906         atomic_dec(&dev->refcnt);
907
908         return 0;
909 }
910
911 static int w1_init(void)
912 {
913         int retval;
914
915         printk(KERN_INFO "Driver for 1-wire Dallas network protocol.\n");
916
917         w1_init_netlink();
918
919         retval = bus_register(&w1_bus_type);
920         if (retval) {
921                 printk(KERN_ERR "Failed to register bus. err=%d.\n", retval);
922                 goto err_out_exit_init;
923         }
924
925         retval = driver_register(&w1_master_driver);
926         if (retval) {
927                 printk(KERN_ERR
928                         "Failed to register master driver. err=%d.\n",
929                         retval);
930                 goto err_out_bus_unregister;
931         }
932
933         retval = driver_register(&w1_slave_driver);
934         if (retval) {
935                 printk(KERN_ERR
936                         "Failed to register master driver. err=%d.\n",
937                         retval);
938                 goto err_out_master_unregister;
939         }
940
941         w1_control_thread = kthread_run(w1_control, NULL, "w1_control");
942         if (IS_ERR(w1_control_thread)) {
943                 retval = PTR_ERR(w1_control_thread);
944                 printk(KERN_ERR "Failed to create control thread. err=%d\n",
945                         retval);
946                 goto err_out_slave_unregister;
947         }
948
949         return 0;
950
951 err_out_slave_unregister:
952         driver_unregister(&w1_slave_driver);
953
954 err_out_master_unregister:
955         driver_unregister(&w1_master_driver);
956
957 err_out_bus_unregister:
958         bus_unregister(&w1_bus_type);
959
960 err_out_exit_init:
961         return retval;
962 }
963
964 static void w1_fini(void)
965 {
966         struct w1_master *dev;
967
968         list_for_each_entry(dev, &w1_masters, w1_master_entry)
969                 __w1_remove_master_device(dev);
970
971         w1_fini_netlink();
972
973         kthread_stop(w1_control_thread);
974
975         driver_unregister(&w1_slave_driver);
976         driver_unregister(&w1_master_driver);
977         bus_unregister(&w1_bus_type);
978 }
979
980 module_init(w1_init);
981 module_exit(w1_fini);