Documentation: make configfs example code simpler, clearer
[linux-3.10.git] / Documentation / filesystems / configfs / configfs_example_explicit.c
1 /*
2  * vim: noexpandtab ts=8 sts=0 sw=8:
3  *
4  * configfs_example_explicit.c - This file is a demonstration module
5  *      containing a number of configfs subsystems.  It explicitly defines
6  *      each structure without using the helper macros defined in
7  *      configfs.h.
8  *
9  * This program is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU General Public
11  * License as published by the Free Software Foundation; either
12  * version 2 of the License, or (at your option) any later version.
13  *
14  * This program is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17  * General Public License for more details.
18  *
19  * You should have received a copy of the GNU General Public
20  * License along with this program; if not, write to the
21  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
22  * Boston, MA 021110-1307, USA.
23  *
24  * Based on sysfs:
25  *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
26  *
27  * configfs Copyright (C) 2005 Oracle.  All rights reserved.
28  */
29
30 #include <linux/init.h>
31 #include <linux/module.h>
32 #include <linux/slab.h>
33
34 #include <linux/configfs.h>
35
36
37
38 /*
39  * 01-childless
40  *
41  * This first example is a childless subsystem.  It cannot create
42  * any config_items.  It just has attributes.
43  *
44  * Note that we are enclosing the configfs_subsystem inside a container.
45  * This is not necessary if a subsystem has no attributes directly
46  * on the subsystem.  See the next example, 02-simple-children, for
47  * such a subsystem.
48  */
49
50 struct childless {
51         struct configfs_subsystem subsys;
52         int showme;
53         int storeme;
54 };
55
56 struct childless_attribute {
57         struct configfs_attribute attr;
58         ssize_t (*show)(struct childless *, char *);
59         ssize_t (*store)(struct childless *, const char *, size_t);
60 };
61
62 static inline struct childless *to_childless(struct config_item *item)
63 {
64         return item ? container_of(to_configfs_subsystem(to_config_group(item)), struct childless, subsys) : NULL;
65 }
66
67 static ssize_t childless_showme_read(struct childless *childless,
68                                      char *page)
69 {
70         ssize_t pos;
71
72         pos = sprintf(page, "%d\n", childless->showme);
73         childless->showme++;
74
75         return pos;
76 }
77
78 static ssize_t childless_storeme_read(struct childless *childless,
79                                       char *page)
80 {
81         return sprintf(page, "%d\n", childless->storeme);
82 }
83
84 static ssize_t childless_storeme_write(struct childless *childless,
85                                        const char *page,
86                                        size_t count)
87 {
88         unsigned long tmp;
89         char *p = (char *) page;
90
91         tmp = simple_strtoul(p, &p, 10);
92         if ((*p != '\0') && (*p != '\n'))
93                 return -EINVAL;
94
95         if (tmp > INT_MAX)
96                 return -ERANGE;
97
98         childless->storeme = tmp;
99
100         return count;
101 }
102
103 static ssize_t childless_description_read(struct childless *childless,
104                                           char *page)
105 {
106         return sprintf(page,
107 "[01-childless]\n"
108 "\n"
109 "The childless subsystem is the simplest possible subsystem in\n"
110 "configfs.  It does not support the creation of child config_items.\n"
111 "It only has a few attributes.  In fact, it isn't much different\n"
112 "than a directory in /proc.\n");
113 }
114
115 static struct childless_attribute childless_attr_showme = {
116         .attr   = { .ca_owner = THIS_MODULE, .ca_name = "showme", .ca_mode = S_IRUGO },
117         .show   = childless_showme_read,
118 };
119 static struct childless_attribute childless_attr_storeme = {
120         .attr   = { .ca_owner = THIS_MODULE, .ca_name = "storeme", .ca_mode = S_IRUGO | S_IWUSR },
121         .show   = childless_storeme_read,
122         .store  = childless_storeme_write,
123 };
124 static struct childless_attribute childless_attr_description = {
125         .attr = { .ca_owner = THIS_MODULE, .ca_name = "description", .ca_mode = S_IRUGO },
126         .show = childless_description_read,
127 };
128
129 static struct configfs_attribute *childless_attrs[] = {
130         &childless_attr_showme.attr,
131         &childless_attr_storeme.attr,
132         &childless_attr_description.attr,
133         NULL,
134 };
135
136 static ssize_t childless_attr_show(struct config_item *item,
137                                    struct configfs_attribute *attr,
138                                    char *page)
139 {
140         struct childless *childless = to_childless(item);
141         struct childless_attribute *childless_attr =
142                 container_of(attr, struct childless_attribute, attr);
143         ssize_t ret = 0;
144
145         if (childless_attr->show)
146                 ret = childless_attr->show(childless, page);
147         return ret;
148 }
149
150 static ssize_t childless_attr_store(struct config_item *item,
151                                     struct configfs_attribute *attr,
152                                     const char *page, size_t count)
153 {
154         struct childless *childless = to_childless(item);
155         struct childless_attribute *childless_attr =
156                 container_of(attr, struct childless_attribute, attr);
157         ssize_t ret = -EINVAL;
158
159         if (childless_attr->store)
160                 ret = childless_attr->store(childless, page, count);
161         return ret;
162 }
163
164 static struct configfs_item_operations childless_item_ops = {
165         .show_attribute         = childless_attr_show,
166         .store_attribute        = childless_attr_store,
167 };
168
169 static struct config_item_type childless_type = {
170         .ct_item_ops    = &childless_item_ops,
171         .ct_attrs       = childless_attrs,
172         .ct_owner       = THIS_MODULE,
173 };
174
175 static struct childless childless_subsys = {
176         .subsys = {
177                 .su_group = {
178                         .cg_item = {
179                                 .ci_namebuf = "01-childless",
180                                 .ci_type = &childless_type,
181                         },
182                 },
183         },
184 };
185
186
187 /* ----------------------------------------------------------------- */
188
189 /*
190  * 02-simple-children
191  *
192  * This example merely has a simple one-attribute child.  Note that
193  * there is no extra attribute structure, as the child's attribute is
194  * known from the get-go.  Also, there is no container for the
195  * subsystem, as it has no attributes of its own.
196  */
197
198 struct simple_child {
199         struct config_item item;
200         int storeme;
201 };
202
203 static inline struct simple_child *to_simple_child(struct config_item *item)
204 {
205         return item ? container_of(item, struct simple_child, item) : NULL;
206 }
207
208 static struct configfs_attribute simple_child_attr_storeme = {
209         .ca_owner = THIS_MODULE,
210         .ca_name = "storeme",
211         .ca_mode = S_IRUGO | S_IWUSR,
212 };
213
214 static struct configfs_attribute *simple_child_attrs[] = {
215         &simple_child_attr_storeme,
216         NULL,
217 };
218
219 static ssize_t simple_child_attr_show(struct config_item *item,
220                                       struct configfs_attribute *attr,
221                                       char *page)
222 {
223         ssize_t count;
224         struct simple_child *simple_child = to_simple_child(item);
225
226         count = sprintf(page, "%d\n", simple_child->storeme);
227
228         return count;
229 }
230
231 static ssize_t simple_child_attr_store(struct config_item *item,
232                                        struct configfs_attribute *attr,
233                                        const char *page, size_t count)
234 {
235         struct simple_child *simple_child = to_simple_child(item);
236         unsigned long tmp;
237         char *p = (char *) page;
238
239         tmp = simple_strtoul(p, &p, 10);
240         if (!p || (*p && (*p != '\n')))
241                 return -EINVAL;
242
243         if (tmp > INT_MAX)
244                 return -ERANGE;
245
246         simple_child->storeme = tmp;
247
248         return count;
249 }
250
251 static void simple_child_release(struct config_item *item)
252 {
253         kfree(to_simple_child(item));
254 }
255
256 static struct configfs_item_operations simple_child_item_ops = {
257         .release                = simple_child_release,
258         .show_attribute         = simple_child_attr_show,
259         .store_attribute        = simple_child_attr_store,
260 };
261
262 static struct config_item_type simple_child_type = {
263         .ct_item_ops    = &simple_child_item_ops,
264         .ct_attrs       = simple_child_attrs,
265         .ct_owner       = THIS_MODULE,
266 };
267
268
269 struct simple_children {
270         struct config_group group;
271 };
272
273 static inline struct simple_children *to_simple_children(struct config_item *item)
274 {
275         return item ? container_of(to_config_group(item), struct simple_children, group) : NULL;
276 }
277
278 static struct config_item *simple_children_make_item(struct config_group *group, const char *name)
279 {
280         struct simple_child *simple_child;
281
282         simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL);
283         if (!simple_child)
284                 return ERR_PTR(-ENOMEM);
285
286         config_item_init_type_name(&simple_child->item, name,
287                                    &simple_child_type);
288
289         simple_child->storeme = 0;
290
291         return &simple_child->item;
292 }
293
294 static struct configfs_attribute simple_children_attr_description = {
295         .ca_owner = THIS_MODULE,
296         .ca_name = "description",
297         .ca_mode = S_IRUGO,
298 };
299
300 static struct configfs_attribute *simple_children_attrs[] = {
301         &simple_children_attr_description,
302         NULL,
303 };
304
305 static ssize_t simple_children_attr_show(struct config_item *item,
306                                          struct configfs_attribute *attr,
307                                          char *page)
308 {
309         return sprintf(page,
310 "[02-simple-children]\n"
311 "\n"
312 "This subsystem allows the creation of child config_items.  These\n"
313 "items have only one attribute that is readable and writeable.\n");
314 }
315
316 static void simple_children_release(struct config_item *item)
317 {
318         kfree(to_simple_children(item));
319 }
320
321 static struct configfs_item_operations simple_children_item_ops = {
322         .release        = simple_children_release,
323         .show_attribute = simple_children_attr_show,
324 };
325
326 /*
327  * Note that, since no extra work is required on ->drop_item(),
328  * no ->drop_item() is provided.
329  */
330 static struct configfs_group_operations simple_children_group_ops = {
331         .make_item      = simple_children_make_item,
332 };
333
334 static struct config_item_type simple_children_type = {
335         .ct_item_ops    = &simple_children_item_ops,
336         .ct_group_ops   = &simple_children_group_ops,
337         .ct_attrs       = simple_children_attrs,
338         .ct_owner       = THIS_MODULE,
339 };
340
341 static struct configfs_subsystem simple_children_subsys = {
342         .su_group = {
343                 .cg_item = {
344                         .ci_namebuf = "02-simple-children",
345                         .ci_type = &simple_children_type,
346                 },
347         },
348 };
349
350
351 /* ----------------------------------------------------------------- */
352
353 /*
354  * 03-group-children
355  *
356  * This example reuses the simple_children group from above.  However,
357  * the simple_children group is not the subsystem itself, it is a
358  * child of the subsystem.  Creation of a group in the subsystem creates
359  * a new simple_children group.  That group can then have simple_child
360  * children of its own.
361  */
362
363 static struct config_group *group_children_make_group(struct config_group *group, const char *name)
364 {
365         struct simple_children *simple_children;
366
367         simple_children = kzalloc(sizeof(struct simple_children),
368                                   GFP_KERNEL);
369         if (!simple_children)
370                 return ERR_PTR(-ENOMEM);
371
372         config_group_init_type_name(&simple_children->group, name,
373                                     &simple_children_type);
374
375         return &simple_children->group;
376 }
377
378 static struct configfs_attribute group_children_attr_description = {
379         .ca_owner = THIS_MODULE,
380         .ca_name = "description",
381         .ca_mode = S_IRUGO,
382 };
383
384 static struct configfs_attribute *group_children_attrs[] = {
385         &group_children_attr_description,
386         NULL,
387 };
388
389 static ssize_t group_children_attr_show(struct config_item *item,
390                                         struct configfs_attribute *attr,
391                                         char *page)
392 {
393         return sprintf(page,
394 "[03-group-children]\n"
395 "\n"
396 "This subsystem allows the creation of child config_groups.  These\n"
397 "groups are like the subsystem simple-children.\n");
398 }
399
400 static struct configfs_item_operations group_children_item_ops = {
401         .show_attribute = group_children_attr_show,
402 };
403
404 /*
405  * Note that, since no extra work is required on ->drop_item(),
406  * no ->drop_item() is provided.
407  */
408 static struct configfs_group_operations group_children_group_ops = {
409         .make_group     = group_children_make_group,
410 };
411
412 static struct config_item_type group_children_type = {
413         .ct_item_ops    = &group_children_item_ops,
414         .ct_group_ops   = &group_children_group_ops,
415         .ct_attrs       = group_children_attrs,
416         .ct_owner       = THIS_MODULE,
417 };
418
419 static struct configfs_subsystem group_children_subsys = {
420         .su_group = {
421                 .cg_item = {
422                         .ci_namebuf = "03-group-children",
423                         .ci_type = &group_children_type,
424                 },
425         },
426 };
427
428 /* ----------------------------------------------------------------- */
429
430 /*
431  * We're now done with our subsystem definitions.
432  * For convenience in this module, here's a list of them all.  It
433  * allows the init function to easily register them.  Most modules
434  * will only have one subsystem, and will only call register_subsystem
435  * on it directly.
436  */
437 static struct configfs_subsystem *example_subsys[] = {
438         &childless_subsys.subsys,
439         &simple_children_subsys,
440         &group_children_subsys,
441         NULL,
442 };
443
444 static int __init configfs_example_init(void)
445 {
446         int ret;
447         int i;
448         struct configfs_subsystem *subsys;
449
450         for (i = 0; example_subsys[i]; i++) {
451                 subsys = example_subsys[i];
452
453                 config_group_init(&subsys->su_group);
454                 mutex_init(&subsys->su_mutex);
455                 ret = configfs_register_subsystem(subsys);
456                 if (ret) {
457                         printk(KERN_ERR "Error %d while registering subsystem %s\n",
458                                ret,
459                                subsys->su_group.cg_item.ci_namebuf);
460                         goto out_unregister;
461                 }
462         }
463
464         return 0;
465
466 out_unregister:
467         for (; i >= 0; i--) {
468                 configfs_unregister_subsystem(example_subsys[i]);
469         }
470
471         return ret;
472 }
473
474 static void __exit configfs_example_exit(void)
475 {
476         int i;
477
478         for (i = 0; example_subsys[i]; i++) {
479                 configfs_unregister_subsystem(example_subsys[i]);
480         }
481 }
482
483 module_init(configfs_example_init);
484 module_exit(configfs_example_exit);
485 MODULE_LICENSE("GPL");