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