1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * vim: noexpandtab ts=8 sts=0 sw=8:
4  *
5  * configfs_example_macros.c - This file is a demonstration module
6  *      containing a number of configfs subsystems.  It uses the helper
7  *      macros defined by configfs.h
8  *
9  * Based on sysfs:
10  *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
11  *
12  * configfs Copyright (C) 2005 Oracle.  All rights reserved.
13  */
14 
15 #include <linux/init.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/configfs.h>
20 
21 /*
22  * 01-childless
23  *
24  * This first example is a childless subsystem.  It cannot create
25  * any config_items.  It just has attributes.
26  *
27  * Note that we are enclosing the configfs_subsystem inside a container.
28  * This is not necessary if a subsystem has no attributes directly
29  * on the subsystem.  See the next example, 02-simple-children, for
30  * such a subsystem.
31  */
32 
33 struct childless {
34 	struct configfs_subsystem subsys;
35 	int showme;
36 	int storeme;
37 };
38 
39 static inline struct childless *to_childless(struct config_item *item)
40 {
41 	return container_of(to_configfs_subsystem(to_config_group(item)),
42 			    struct childless, subsys);
43 }
44 
45 static ssize_t childless_showme_show(struct config_item *item, char *page)
46 {
47 	struct childless *childless = to_childless(item);
48 	ssize_t pos;
49 
50 	pos = sprintf(page, "%d\n", childless->showme);
51 	childless->showme++;
52 
53 	return pos;
54 }
55 
56 static ssize_t childless_storeme_show(struct config_item *item, char *page)
57 {
58 	return sprintf(page, "%d\n", to_childless(item)->storeme);
59 }
60 
61 static ssize_t childless_storeme_store(struct config_item *item,
62 		const char *page, size_t count)
63 {
64 	struct childless *childless = to_childless(item);
65 	int ret;
66 
67 	ret = kstrtoint(page, 10, &childless->storeme);
68 	if (ret)
69 		return ret;
70 
71 	return count;
72 }
73 
74 static ssize_t childless_description_show(struct config_item *item, char *page)
75 {
76 	return sprintf(page,
77 "[01-childless]\n"
78 "\n"
79 "The childless subsystem is the simplest possible subsystem in\n"
80 "configfs.  It does not support the creation of child config_items.\n"
81 "It only has a few attributes.  In fact, it isn't much different\n"
82 "than a directory in /proc.\n");
83 }
84 
85 CONFIGFS_ATTR_RO(childless_, showme);
86 CONFIGFS_ATTR(childless_, storeme);
87 CONFIGFS_ATTR_RO(childless_, description);
88 
89 static struct configfs_attribute *childless_attrs[] = {
90 	&childless_attr_showme,
91 	&childless_attr_storeme,
92 	&childless_attr_description,
93 	NULL,
94 };
95 
96 static const struct config_item_type childless_type = {
97 	.ct_attrs	= childless_attrs,
98 	.ct_owner	= THIS_MODULE,
99 };
100 
101 static struct childless childless_subsys = {
102 	.subsys = {
103 		.su_group = {
104 			.cg_item = {
105 				.ci_namebuf = "01-childless",
106 				.ci_type = &childless_type,
107 			},
108 		},
109 	},
110 };
111 
112 /* ----------------------------------------------------------------- */
113 
114 /*
115  * 02-simple-children
116  *
117  * This example merely has a simple one-attribute child.  Note that
118  * there is no extra attribute structure, as the child's attribute is
119  * known from the get-go.  Also, there is no container for the
120  * subsystem, as it has no attributes of its own.
121  */
122 
123 struct simple_child {
124 	struct config_item item;
125 	int storeme;
126 };
127 
128 static inline struct simple_child *to_simple_child(struct config_item *item)
129 {
130 	return container_of(item, struct simple_child, item);
131 }
132 
133 static ssize_t simple_child_storeme_show(struct config_item *item, char *page)
134 {
135 	return sprintf(page, "%d\n", to_simple_child(item)->storeme);
136 }
137 
138 static ssize_t simple_child_storeme_store(struct config_item *item,
139 		const char *page, size_t count)
140 {
141 	struct simple_child *simple_child = to_simple_child(item);
142 	int ret;
143 
144 	ret = kstrtoint(page, 10, &simple_child->storeme);
145 	if (ret)
146 		return ret;
147 
148 	return count;
149 }
150 
151 CONFIGFS_ATTR(simple_child_, storeme);
152 
153 static struct configfs_attribute *simple_child_attrs[] = {
154 	&simple_child_attr_storeme,
155 	NULL,
156 };
157 
158 static void simple_child_release(struct config_item *item)
159 {
160 	kfree(to_simple_child(item));
161 }
162 
163 static struct configfs_item_operations simple_child_item_ops = {
164 	.release	= simple_child_release,
165 };
166 
167 static const struct config_item_type simple_child_type = {
168 	.ct_item_ops	= &simple_child_item_ops,
169 	.ct_attrs	= simple_child_attrs,
170 	.ct_owner	= THIS_MODULE,
171 };
172 
173 struct simple_children {
174 	struct config_group group;
175 };
176 
177 static inline struct simple_children *to_simple_children(struct config_item *item)
178 {
179 	return container_of(to_config_group(item),
180 			    struct simple_children, group);
181 }
182 
183 static struct config_item *simple_children_make_item(struct config_group *group,
184 		const char *name)
185 {
186 	struct simple_child *simple_child;
187 
188 	simple_child = kzalloc(sizeof(struct simple_child), GFP_KERNEL);
189 	if (!simple_child)
190 		return ERR_PTR(-ENOMEM);
191 
192 	config_item_init_type_name(&simple_child->item, name,
193 				   &simple_child_type);
194 
195 	return &simple_child->item;
196 }
197 
198 static ssize_t simple_children_description_show(struct config_item *item,
199 		char *page)
200 {
201 	return sprintf(page,
202 "[02-simple-children]\n"
203 "\n"
204 "This subsystem allows the creation of child config_items.  These\n"
205 "items have only one attribute that is readable and writeable.\n");
206 }
207 
208 CONFIGFS_ATTR_RO(simple_children_, description);
209 
210 static struct configfs_attribute *simple_children_attrs[] = {
211 	&simple_children_attr_description,
212 	NULL,
213 };
214 
215 static void simple_children_release(struct config_item *item)
216 {
217 	kfree(to_simple_children(item));
218 }
219 
220 static struct configfs_item_operations simple_children_item_ops = {
221 	.release	= simple_children_release,
222 };
223 
224 /*
225  * Note that, since no extra work is required on ->drop_item(),
226  * no ->drop_item() is provided.
227  */
228 static struct configfs_group_operations simple_children_group_ops = {
229 	.make_item	= simple_children_make_item,
230 };
231 
232 static const struct config_item_type simple_children_type = {
233 	.ct_item_ops	= &simple_children_item_ops,
234 	.ct_group_ops	= &simple_children_group_ops,
235 	.ct_attrs	= simple_children_attrs,
236 	.ct_owner	= THIS_MODULE,
237 };
238 
239 static struct configfs_subsystem simple_children_subsys = {
240 	.su_group = {
241 		.cg_item = {
242 			.ci_namebuf = "02-simple-children",
243 			.ci_type = &simple_children_type,
244 		},
245 	},
246 };
247 
248 /* ----------------------------------------------------------------- */
249 
250 /*
251  * 03-group-children
252  *
253  * This example reuses the simple_children group from above.  However,
254  * the simple_children group is not the subsystem itself, it is a
255  * child of the subsystem.  Creation of a group in the subsystem creates
256  * a new simple_children group.  That group can then have simple_child
257  * children of its own.
258  */
259 
260 static struct config_group *group_children_make_group(
261 		struct config_group *group, const char *name)
262 {
263 	struct simple_children *simple_children;
264 
265 	simple_children = kzalloc(sizeof(struct simple_children),
266 				  GFP_KERNEL);
267 	if (!simple_children)
268 		return ERR_PTR(-ENOMEM);
269 
270 	config_group_init_type_name(&simple_children->group, name,
271 				    &simple_children_type);
272 
273 	return &simple_children->group;
274 }
275 
276 static ssize_t group_children_description_show(struct config_item *item,
277 		char *page)
278 {
279 	return sprintf(page,
280 "[03-group-children]\n"
281 "\n"
282 "This subsystem allows the creation of child config_groups.  These\n"
283 "groups are like the subsystem simple-children.\n");
284 }
285 
286 CONFIGFS_ATTR_RO(group_children_, description);
287 
288 static struct configfs_attribute *group_children_attrs[] = {
289 	&group_children_attr_description,
290 	NULL,
291 };
292 
293 /*
294  * Note that, since no extra work is required on ->drop_item(),
295  * no ->drop_item() is provided.
296  */
297 static struct configfs_group_operations group_children_group_ops = {
298 	.make_group	= group_children_make_group,
299 };
300 
301 static const struct config_item_type group_children_type = {
302 	.ct_group_ops	= &group_children_group_ops,
303 	.ct_attrs	= group_children_attrs,
304 	.ct_owner	= THIS_MODULE,
305 };
306 
307 static struct configfs_subsystem group_children_subsys = {
308 	.su_group = {
309 		.cg_item = {
310 			.ci_namebuf = "03-group-children",
311 			.ci_type = &group_children_type,
312 		},
313 	},
314 };
315 
316 /* ----------------------------------------------------------------- */
317 
318 /*
319  * We're now done with our subsystem definitions.
320  * For convenience in this module, here's a list of them all.  It
321  * allows the init function to easily register them.  Most modules
322  * will only have one subsystem, and will only call register_subsystem
323  * on it directly.
324  */
325 static struct configfs_subsystem *example_subsys[] = {
326 	&childless_subsys.subsys,
327 	&simple_children_subsys,
328 	&group_children_subsys,
329 	NULL,
330 };
331 
332 static int __init configfs_example_init(void)
333 {
334 	struct configfs_subsystem *subsys;
335 	int ret, i;
336 
337 	for (i = 0; example_subsys[i]; i++) {
338 		subsys = example_subsys[i];
339 
340 		config_group_init(&subsys->su_group);
341 		mutex_init(&subsys->su_mutex);
342 		ret = configfs_register_subsystem(subsys);
343 		if (ret) {
344 			pr_err("Error %d while registering subsystem %s\n",
345 			       ret, subsys->su_group.cg_item.ci_namebuf);
346 			goto out_unregister;
347 		}
348 	}
349 
350 	return 0;
351 
352 out_unregister:
353 	for (i--; i >= 0; i--)
354 		configfs_unregister_subsystem(example_subsys[i]);
355 
356 	return ret;
357 }
358 
359 static void __exit configfs_example_exit(void)
360 {
361 	int i;
362 
363 	for (i = 0; example_subsys[i]; i++)
364 		configfs_unregister_subsystem(example_subsys[i]);
365 }
366 
367 module_init(configfs_example_init);
368 module_exit(configfs_example_exit);
369 MODULE_LICENSE("GPL");
370