projects/linux·blob master · refs

489 lines · 12.1 KiB

1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * configfs_example_macros.c - This file is a demonstration module
4 * containing a number of configfs subsystems. It uses the helper
5 * macros defined by configfs.h
6 *
7 * Based on sysfs:
8 * sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
9 *
10 * configfs Copyright (C) 2005 Oracle. All rights reserved.
11 */
12
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/slab.h>
17#include <linux/configfs.h>
18
19/*
20 * 01-childless
21 *
22 * This first example is a childless subsystem. It cannot create
23 * any config_items. It just has attributes.
24 *
25 * Note that we are enclosing the configfs_subsystem inside a container.
26 * This is not necessary if a subsystem has no attributes directly
27 * on the subsystem. See the next example, 02-simple-children, for
28 * such a subsystem.
29 */
30
31struct childless {
32 struct configfs_subsystem subsys;
33 int showme;
34 int storeme;
35};
36
37static inline struct childless *to_childless(struct config_item *item)
38{
39 return container_of(to_configfs_subsystem(to_config_group(item)),
40 struct childless, subsys);
41}
42
43static ssize_t childless_showme_show(struct config_item *item, char *page)
44{
45 struct childless *childless = to_childless(item);
46 ssize_t pos;
47
48 pos = sprintf(page, "%d\n", childless->showme);
49 childless->showme++;
50
51 return pos;
52}
53
54static ssize_t childless_storeme_show(struct config_item *item, char *page)
55{
56 return sprintf(page, "%d\n", to_childless(item)->storeme);
57}
58
59static ssize_t childless_storeme_store(struct config_item *item,
60 const char *page, size_t count)
61{
62 struct childless *childless = to_childless(item);
63 int ret;
64
65 ret = kstrtoint(page, 10, &childless->storeme);
66 if (ret)
67 return ret;
68
69 return count;
70}
71
72static ssize_t childless_description_show(struct config_item *item, char *page)
73{
74 return sprintf(page,
75"[01-childless]\n"
76"\n"
77"The childless subsystem is the simplest possible subsystem in\n"
78"configfs. It does not support the creation of child config_items.\n"
79"It only has a few attributes. In fact, it isn't much different\n"
80"than a directory in /proc.\n");
81}
82
83CONFIGFS_ATTR_RO(childless_, showme);
84CONFIGFS_ATTR(childless_, storeme);
85CONFIGFS_ATTR_RO(childless_, description);
86
87static const struct configfs_attribute *const childless_attrs[] = {
88 &childless_attr_showme,
89 &childless_attr_storeme,
90 &childless_attr_description,
91 NULL,
92};
93
94static const struct config_item_type childless_type = {
95 .ct_attrs_const = childless_attrs,
96 .ct_owner = THIS_MODULE,
97};
98
99static struct childless childless_subsys = {
100 .subsys = {
101 .su_group = {
102 .cg_item = {
103 .ci_namebuf = "01-childless",
104 .ci_type = &childless_type,
105 },
106 },
107 },
108};
109
110/* ----------------------------------------------------------------- */
111
112/*
113 * 02-simple-children
114 *
115 * This example merely has a simple one-attribute child. Note that
116 * there is no extra attribute structure, as the child's attribute is
117 * known from the get-go. Also, there is no container for the
118 * subsystem, as it has no attributes of its own.
119 */
120
121struct simple_child {
122 struct config_item item;
123 int storeme;
124};
125
126static inline struct simple_child *to_simple_child(struct config_item *item)
127{
128 return container_of(item, struct simple_child, item);
129}
130
131static ssize_t simple_child_storeme_show(struct config_item *item, char *page)
132{
133 return sprintf(page, "%d\n", to_simple_child(item)->storeme);
134}
135
136static ssize_t simple_child_storeme_store(struct config_item *item,
137 const char *page, size_t count)
138{
139 struct simple_child *simple_child = to_simple_child(item);
140 int ret;
141
142 ret = kstrtoint(page, 10, &simple_child->storeme);
143 if (ret)
144 return ret;
145
146 return count;
147}
148
149CONFIGFS_ATTR(simple_child_, storeme);
150
151static const struct configfs_attribute *const simple_child_attrs[] = {
152 &simple_child_attr_storeme,
153 NULL,
154};
155
156static void simple_child_release(struct config_item *item)
157{
158 kfree(to_simple_child(item));
159}
160
161static const struct configfs_item_operations simple_child_item_ops = {
162 .release = simple_child_release,
163};
164
165static const struct config_item_type simple_child_type = {
166 .ct_item_ops = &simple_child_item_ops,
167 .ct_attrs_const = simple_child_attrs,
168 .ct_owner = THIS_MODULE,
169};
170
171struct simple_children {
172 struct config_group group;
173};
174
175static inline struct simple_children *to_simple_children(struct config_item *item)
176{
177 return container_of(to_config_group(item),
178 struct simple_children, group);
179}
180
181static struct config_item *simple_children_make_item(struct config_group *group,
182 const char *name)
183{
184 struct simple_child *simple_child;
185
186 simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL);
187 if (!simple_child)
188 return ERR_PTR(-ENOMEM);
189
190 config_item_init_type_name(&simple_child->item, name,
191 &simple_child_type);
192
193 return &simple_child->item;
194}
195
196static ssize_t simple_children_description_show(struct config_item *item,
197 char *page)
198{
199 return sprintf(page,
200"[02-simple-children]\n"
201"\n"
202"This subsystem allows the creation of child config_items. These\n"
203"items have only one attribute that is readable and writeable.\n");
204}
205
206CONFIGFS_ATTR_RO(simple_children_, description);
207
208static const struct configfs_attribute *const simple_children_attrs[] = {
209 &simple_children_attr_description,
210 NULL,
211};
212
213static void simple_children_release(struct config_item *item)
214{
215 kfree(to_simple_children(item));
216}
217
218static const struct configfs_item_operations simple_children_item_ops = {
219 .release = simple_children_release,
220};
221
222/*
223 * Note that, since no extra work is required on ->drop_item(),
224 * no ->drop_item() is provided.
225 */
226static const struct configfs_group_operations simple_children_group_ops = {
227 .make_item = simple_children_make_item,
228};
229
230static const struct config_item_type simple_children_type = {
231 .ct_item_ops = &simple_children_item_ops,
232 .ct_group_ops = &simple_children_group_ops,
233 .ct_attrs_const = simple_children_attrs,
234 .ct_owner = THIS_MODULE,
235};
236
237static struct configfs_subsystem simple_children_subsys = {
238 .su_group = {
239 .cg_item = {
240 .ci_namebuf = "02-simple-children",
241 .ci_type = &simple_children_type,
242 },
243 },
244};
245
246/* ----------------------------------------------------------------- */
247
248/*
249 * 03-group-children
250 *
251 * This example reuses the simple_children group from above. However,
252 * the simple_children group is not the subsystem itself, it is a
253 * child of the subsystem. Creation of a group in the subsystem creates
254 * a new simple_children group. That group can then have simple_child
255 * children of its own.
256 */
257
258static struct config_group *group_children_make_group(
259 struct config_group *group, const char *name)
260{
261 struct simple_children *simple_children;
262
263 simple_children = kzalloc(sizeof(struct simple_children),
264 GFP_KERNEL);
265 if (!simple_children)
266 return ERR_PTR(-ENOMEM);
267
268 config_group_init_type_name(&simple_children->group, name,
269 &simple_children_type);
270
271 return &simple_children->group;
272}
273
274static ssize_t group_children_description_show(struct config_item *item,
275 char *page)
276{
277 return sprintf(page,
278"[03-group-children]\n"
279"\n"
280"This subsystem allows the creation of child config_groups. These\n"
281"groups are like the subsystem simple-children.\n");
282}
283
284CONFIGFS_ATTR_RO(group_children_, description);
285
286static const struct configfs_attribute *const group_children_attrs[] = {
287 &group_children_attr_description,
288 NULL,
289};
290
291/*
292 * Note that, since no extra work is required on ->drop_item(),
293 * no ->drop_item() is provided.
294 */
295static const struct configfs_group_operations group_children_group_ops = {
296 .make_group = group_children_make_group,
297};
298
299static const struct config_item_type group_children_type = {
300 .ct_group_ops = &group_children_group_ops,
301 .ct_attrs_const = group_children_attrs,
302 .ct_owner = THIS_MODULE,
303};
304
305static struct configfs_subsystem group_children_subsys = {
306 .su_group = {
307 .cg_item = {
308 .ci_namebuf = "03-group-children",
309 .ci_type = &group_children_type,
310 },
311 },
312};
313
314/* ----------------------------------------------------------------- */
315
316/*
317 * 04-symlink-children
318 *
319 * This example has children that are valid sources for symlink(2). A
320 * child accepts a link to any other config_item and reports how many
321 * links it currently holds, so ->allow_link() and ->drop_link() are
322 * observable from userspace.
323 */
324
325struct symlink_child {
326 struct config_item item;
327 int nlinks;
328};
329
330static inline struct symlink_child *to_symlink_child(struct config_item *item)
331{
332 return container_of(item, struct symlink_child, item);
333}
334
335static ssize_t symlink_child_nlinks_show(struct config_item *item, char *page)
336{
337 return sprintf(page, "%d\n", to_symlink_child(item)->nlinks);
338}
339
340CONFIGFS_ATTR_RO(symlink_child_, nlinks);
341
342static struct configfs_attribute *symlink_child_attrs[] = {
343 &symlink_child_attr_nlinks,
344 NULL,
345};
346
347/*
348 * The VFS holds the source item's directory locked across symlink(2) and
349 * unlink(2), so ->nlinks needs no lock of its own.
350 */
351static int symlink_child_allow_link(struct config_item *src,
352 struct config_item *target)
353{
354 to_symlink_child(src)->nlinks++;
355
356 return 0;
357}
358
359static void symlink_child_drop_link(struct config_item *src,
360 struct config_item *target)
361{
362 to_symlink_child(src)->nlinks--;
363}
364
365static void symlink_child_release(struct config_item *item)
366{
367 kfree(to_symlink_child(item));
368}
369
370static const struct configfs_item_operations symlink_child_item_ops = {
371 .release = symlink_child_release,
372 .allow_link = symlink_child_allow_link,
373 .drop_link = symlink_child_drop_link,
374};
375
376static const struct config_item_type symlink_child_type = {
377 .ct_item_ops = &symlink_child_item_ops,
378 .ct_attrs = symlink_child_attrs,
379 .ct_owner = THIS_MODULE,
380};
381
382static struct config_item *symlink_children_make_item(
383 struct config_group *group, const char *name)
384{
385 struct symlink_child *symlink_child;
386
387 symlink_child = kzalloc_obj(*symlink_child, GFP_KERNEL);
388 if (!symlink_child)
389 return ERR_PTR(-ENOMEM);
390
391 config_item_init_type_name(&symlink_child->item, name,
392 &symlink_child_type);
393
394 return &symlink_child->item;
395}
396
397static ssize_t symlink_children_description_show(struct config_item *item,
398 char *page)
399{
400 return sprintf(page,
401"[04-symlink-children]\n"
402"\n"
403"This subsystem allows the creation of child config_items that\n"
404"symlink(2) can point at other config_items from. Each child\n"
405"reports the number of links it holds.\n");
406}
407
408CONFIGFS_ATTR_RO(symlink_children_, description);
409
410static struct configfs_attribute *symlink_children_attrs[] = {
411 &symlink_children_attr_description,
412 NULL,
413};
414
415static const struct configfs_group_operations symlink_children_group_ops = {
416 .make_item = symlink_children_make_item,
417};
418
419static const struct config_item_type symlink_children_type = {
420 .ct_group_ops = &symlink_children_group_ops,
421 .ct_attrs = symlink_children_attrs,
422 .ct_owner = THIS_MODULE,
423};
424
425static struct configfs_subsystem symlink_children_subsys = {
426 .su_group = {
427 .cg_item = {
428 .ci_namebuf = "04-symlink-children",
429 .ci_type = &symlink_children_type,
430 },
431 },
432};
433
434/* ----------------------------------------------------------------- */
435
436/*
437 * We're now done with our subsystem definitions.
438 * For convenience in this module, here's a list of them all. It
439 * allows the init function to easily register them. Most modules
440 * will only have one subsystem, and will only call register_subsystem
441 * on it directly.
442 */
443static struct configfs_subsystem *example_subsys[] = {
444 &childless_subsys.subsys,
445 &simple_children_subsys,
446 &group_children_subsys,
447 &symlink_children_subsys,
448 NULL,
449};
450
451static int __init configfs_example_init(void)
452{
453 struct configfs_subsystem *subsys;
454 int ret, i;
455
456 for (i = 0; example_subsys[i]; i++) {
457 subsys = example_subsys[i];
458
459 config_group_init(&subsys->su_group);
460 mutex_init(&subsys->su_mutex);
461 ret = configfs_register_subsystem(subsys);
462 if (ret) {
463 pr_err("Error %d while registering subsystem %s\n",
464 ret, subsys->su_group.cg_item.ci_namebuf);
465 goto out_unregister;
466 }
467 }
468
469 return 0;
470
471out_unregister:
472 for (i--; i >= 0; i--)
473 configfs_unregister_subsystem(example_subsys[i]);
474
475 return ret;
476}
477
478static void __exit configfs_example_exit(void)
479{
480 int i;
481
482 for (i = 0; example_subsys[i]; i++)
483 configfs_unregister_subsystem(example_subsys[i]);
484}
485
486module_init(configfs_example_init);
487module_exit(configfs_example_exit);
488MODULE_DESCRIPTION("Sample configfs module");
489MODULE_LICENSE("GPL");