Commit | Line | Data |
---|---|---|
d9d16e16 | 1 | // SPDX-License-Identifier: GPL-2.0 |
44bfe16e GKH |
2 | /* |
3 | * Sample kset and ktype implementation | |
4 | * | |
5 | * Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com> | |
6 | * Copyright (C) 2007 Novell Inc. | |
44bfe16e GKH |
7 | */ |
8 | #include <linux/kobject.h> | |
9 | #include <linux/string.h> | |
10 | #include <linux/sysfs.h> | |
5a0e3ad6 | 11 | #include <linux/slab.h> |
44bfe16e GKH |
12 | #include <linux/module.h> |
13 | #include <linux/init.h> | |
14 | ||
15 | /* | |
16 | * This module shows how to create a kset in sysfs called | |
17 | * /sys/kernel/kset-example | |
18 | * Then tree kobjects are created and assigned to this kset, "foo", "baz", | |
19 | * and "bar". In those kobjects, attributes of the same name are also | |
20 | * created and if an integer is written to these files, it can be later | |
21 | * read out of it. | |
22 | */ | |
23 | ||
24 | ||
25 | /* | |
26 | * This is our "object" that we will create a few of and register them with | |
27 | * sysfs. | |
28 | */ | |
29 | struct foo_obj { | |
30 | struct kobject kobj; | |
31 | int foo; | |
32 | int baz; | |
33 | int bar; | |
34 | }; | |
35 | #define to_foo_obj(x) container_of(x, struct foo_obj, kobj) | |
36 | ||
37 | /* a custom attribute that works just for a struct foo_obj. */ | |
38 | struct foo_attribute { | |
39 | struct attribute attr; | |
40 | ssize_t (*show)(struct foo_obj *foo, struct foo_attribute *attr, char *buf); | |
41 | ssize_t (*store)(struct foo_obj *foo, struct foo_attribute *attr, const char *buf, size_t count); | |
42 | }; | |
43 | #define to_foo_attr(x) container_of(x, struct foo_attribute, attr) | |
44 | ||
45 | /* | |
46 | * The default show function that must be passed to sysfs. This will be | |
47 | * called by sysfs for whenever a show function is called by the user on a | |
48 | * sysfs file associated with the kobjects we have registered. We need to | |
49 | * transpose back from a "default" kobject to our custom struct foo_obj and | |
50 | * then call the show function for that specific object. | |
51 | */ | |
52 | static ssize_t foo_attr_show(struct kobject *kobj, | |
53 | struct attribute *attr, | |
54 | char *buf) | |
55 | { | |
56 | struct foo_attribute *attribute; | |
57 | struct foo_obj *foo; | |
58 | ||
59 | attribute = to_foo_attr(attr); | |
60 | foo = to_foo_obj(kobj); | |
61 | ||
62 | if (!attribute->show) | |
63 | return -EIO; | |
64 | ||
65 | return attribute->show(foo, attribute, buf); | |
66 | } | |
67 | ||
68 | /* | |
69 | * Just like the default show function above, but this one is for when the | |
70 | * sysfs "store" is requested (when a value is written to a file.) | |
71 | */ | |
72 | static ssize_t foo_attr_store(struct kobject *kobj, | |
73 | struct attribute *attr, | |
74 | const char *buf, size_t len) | |
75 | { | |
76 | struct foo_attribute *attribute; | |
77 | struct foo_obj *foo; | |
78 | ||
79 | attribute = to_foo_attr(attr); | |
80 | foo = to_foo_obj(kobj); | |
81 | ||
82 | if (!attribute->store) | |
83 | return -EIO; | |
84 | ||
85 | return attribute->store(foo, attribute, buf, len); | |
86 | } | |
87 | ||
88 | /* Our custom sysfs_ops that we will associate with our ktype later on */ | |
52cf25d0 | 89 | static const struct sysfs_ops foo_sysfs_ops = { |
44bfe16e GKH |
90 | .show = foo_attr_show, |
91 | .store = foo_attr_store, | |
92 | }; | |
93 | ||
94 | /* | |
95 | * The release function for our object. This is REQUIRED by the kernel to | |
96 | * have. We free the memory held in our object here. | |
97 | * | |
98 | * NEVER try to get away with just a "blank" release function to try to be | |
99 | * smarter than the kernel. Turns out, no one ever is... | |
100 | */ | |
101 | static void foo_release(struct kobject *kobj) | |
102 | { | |
103 | struct foo_obj *foo; | |
104 | ||
105 | foo = to_foo_obj(kobj); | |
106 | kfree(foo); | |
107 | } | |
108 | ||
109 | /* | |
110 | * The "foo" file where the .foo variable is read from and written to. | |
111 | */ | |
112 | static ssize_t foo_show(struct foo_obj *foo_obj, struct foo_attribute *attr, | |
113 | char *buf) | |
114 | { | |
115 | return sprintf(buf, "%d\n", foo_obj->foo); | |
116 | } | |
117 | ||
118 | static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr, | |
119 | const char *buf, size_t count) | |
120 | { | |
5fd637e7 RB |
121 | int ret; |
122 | ||
123 | ret = kstrtoint(buf, 10, &foo_obj->foo); | |
124 | if (ret < 0) | |
125 | return ret; | |
126 | ||
44bfe16e GKH |
127 | return count; |
128 | } | |
129 | ||
de510989 | 130 | /* Sysfs attributes cannot be world-writable. */ |
44bfe16e | 131 | static struct foo_attribute foo_attribute = |
de510989 | 132 | __ATTR(foo, 0664, foo_show, foo_store); |
44bfe16e GKH |
133 | |
134 | /* | |
20ef9f46 | 135 | * More complex function where we determine which variable is being accessed by |
44bfe16e GKH |
136 | * looking at the attribute for the "baz" and "bar" files. |
137 | */ | |
138 | static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr, | |
139 | char *buf) | |
140 | { | |
141 | int var; | |
142 | ||
143 | if (strcmp(attr->attr.name, "baz") == 0) | |
144 | var = foo_obj->baz; | |
145 | else | |
146 | var = foo_obj->bar; | |
147 | return sprintf(buf, "%d\n", var); | |
148 | } | |
149 | ||
150 | static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr, | |
151 | const char *buf, size_t count) | |
152 | { | |
5fd637e7 RB |
153 | int var, ret; |
154 | ||
155 | ret = kstrtoint(buf, 10, &var); | |
156 | if (ret < 0) | |
157 | return ret; | |
44bfe16e | 158 | |
44bfe16e GKH |
159 | if (strcmp(attr->attr.name, "baz") == 0) |
160 | foo_obj->baz = var; | |
161 | else | |
162 | foo_obj->bar = var; | |
163 | return count; | |
164 | } | |
165 | ||
166 | static struct foo_attribute baz_attribute = | |
de510989 | 167 | __ATTR(baz, 0664, b_show, b_store); |
44bfe16e | 168 | static struct foo_attribute bar_attribute = |
de510989 | 169 | __ATTR(bar, 0664, b_show, b_store); |
44bfe16e GKH |
170 | |
171 | /* | |
20ef9f46 | 172 | * Create a group of attributes so that we can create and destroy them all |
44bfe16e GKH |
173 | * at once. |
174 | */ | |
175 | static struct attribute *foo_default_attrs[] = { | |
176 | &foo_attribute.attr, | |
177 | &baz_attribute.attr, | |
178 | &bar_attribute.attr, | |
179 | NULL, /* need to NULL terminate the list of attributes */ | |
180 | }; | |
c484a678 | 181 | ATTRIBUTE_GROUPS(foo_default); |
44bfe16e GKH |
182 | |
183 | /* | |
184 | * Our own ktype for our kobjects. Here we specify our sysfs ops, the | |
185 | * release function, and the set of default attributes we want created | |
186 | * whenever a kobject of this type is registered with the kernel. | |
187 | */ | |
188 | static struct kobj_type foo_ktype = { | |
189 | .sysfs_ops = &foo_sysfs_ops, | |
190 | .release = foo_release, | |
c484a678 | 191 | .default_groups = foo_default_groups, |
44bfe16e GKH |
192 | }; |
193 | ||
194 | static struct kset *example_kset; | |
195 | static struct foo_obj *foo_obj; | |
196 | static struct foo_obj *bar_obj; | |
197 | static struct foo_obj *baz_obj; | |
198 | ||
199 | static struct foo_obj *create_foo_obj(const char *name) | |
200 | { | |
201 | struct foo_obj *foo; | |
202 | int retval; | |
203 | ||
204 | /* allocate the memory for the whole object */ | |
205 | foo = kzalloc(sizeof(*foo), GFP_KERNEL); | |
206 | if (!foo) | |
207 | return NULL; | |
208 | ||
209 | /* | |
210 | * As we have a kset for this kobject, we need to set it before calling | |
211 | * the kobject core. | |
212 | */ | |
213 | foo->kobj.kset = example_kset; | |
214 | ||
215 | /* | |
216 | * Initialize and add the kobject to the kernel. All the default files | |
217 | * will be created here. As we have already specified a kset for this | |
218 | * kobject, we don't have to set a parent for the kobject, the kobject | |
219 | * will be placed beneath that kset automatically. | |
220 | */ | |
221 | retval = kobject_init_and_add(&foo->kobj, &foo_ktype, NULL, "%s", name); | |
222 | if (retval) { | |
185000fc | 223 | kobject_put(&foo->kobj); |
44bfe16e GKH |
224 | return NULL; |
225 | } | |
226 | ||
227 | /* | |
228 | * We are always responsible for sending the uevent that the kobject | |
229 | * was added to the system. | |
230 | */ | |
231 | kobject_uevent(&foo->kobj, KOBJ_ADD); | |
232 | ||
233 | return foo; | |
234 | } | |
235 | ||
236 | static void destroy_foo_obj(struct foo_obj *foo) | |
237 | { | |
238 | kobject_put(&foo->kobj); | |
239 | } | |
240 | ||
7ec7fb39 | 241 | static int __init example_init(void) |
44bfe16e GKH |
242 | { |
243 | /* | |
244 | * Create a kset with the name of "kset_example", | |
245 | * located under /sys/kernel/ | |
246 | */ | |
247 | example_kset = kset_create_and_add("kset_example", NULL, kernel_kobj); | |
248 | if (!example_kset) | |
249 | return -ENOMEM; | |
250 | ||
251 | /* | |
252 | * Create three objects and register them with our kset | |
253 | */ | |
254 | foo_obj = create_foo_obj("foo"); | |
255 | if (!foo_obj) | |
256 | goto foo_error; | |
257 | ||
258 | bar_obj = create_foo_obj("bar"); | |
259 | if (!bar_obj) | |
260 | goto bar_error; | |
261 | ||
262 | baz_obj = create_foo_obj("baz"); | |
263 | if (!baz_obj) | |
264 | goto baz_error; | |
265 | ||
266 | return 0; | |
267 | ||
268 | baz_error: | |
269 | destroy_foo_obj(bar_obj); | |
270 | bar_error: | |
271 | destroy_foo_obj(foo_obj); | |
272 | foo_error: | |
e756bc56 | 273 | kset_unregister(example_kset); |
44bfe16e GKH |
274 | return -EINVAL; |
275 | } | |
276 | ||
7ec7fb39 | 277 | static void __exit example_exit(void) |
44bfe16e GKH |
278 | { |
279 | destroy_foo_obj(baz_obj); | |
280 | destroy_foo_obj(bar_obj); | |
281 | destroy_foo_obj(foo_obj); | |
282 | kset_unregister(example_kset); | |
283 | } | |
284 | ||
285 | module_init(example_init); | |
286 | module_exit(example_exit); | |
07afb6ac | 287 | MODULE_LICENSE("GPL v2"); |
44bfe16e | 288 | MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>"); |