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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> | |
13 | #include <linux/module.h> | |
14 | #include <linux/init.h> | |
15 | ||
16 | /* | |
17 | * This module shows how to create a kset in sysfs called | |
18 | * /sys/kernel/kset-example | |
19 | * Then tree kobjects are created and assigned to this kset, "foo", "baz", | |
20 | * and "bar". In those kobjects, attributes of the same name are also | |
21 | * created and if an integer is written to these files, it can be later | |
22 | * read out of it. | |
23 | */ | |
24 | ||
25 | ||
26 | /* | |
27 | * This is our "object" that we will create a few of and register them with | |
28 | * sysfs. | |
29 | */ | |
30 | struct foo_obj { | |
31 | struct kobject kobj; | |
32 | int foo; | |
33 | int baz; | |
34 | int bar; | |
35 | }; | |
36 | #define to_foo_obj(x) container_of(x, struct foo_obj, kobj) | |
37 | ||
38 | /* a custom attribute that works just for a struct foo_obj. */ | |
39 | struct foo_attribute { | |
40 | struct attribute attr; | |
41 | ssize_t (*show)(struct foo_obj *foo, struct foo_attribute *attr, char *buf); | |
42 | ssize_t (*store)(struct foo_obj *foo, struct foo_attribute *attr, const char *buf, size_t count); | |
43 | }; | |
44 | #define to_foo_attr(x) container_of(x, struct foo_attribute, attr) | |
45 | ||
46 | /* | |
47 | * The default show function that must be passed to sysfs. This will be | |
48 | * called by sysfs for whenever a show function is called by the user on a | |
49 | * sysfs file associated with the kobjects we have registered. We need to | |
50 | * transpose back from a "default" kobject to our custom struct foo_obj and | |
51 | * then call the show function for that specific object. | |
52 | */ | |
53 | static ssize_t foo_attr_show(struct kobject *kobj, | |
54 | struct attribute *attr, | |
55 | char *buf) | |
56 | { | |
57 | struct foo_attribute *attribute; | |
58 | struct foo_obj *foo; | |
59 | ||
60 | attribute = to_foo_attr(attr); | |
61 | foo = to_foo_obj(kobj); | |
62 | ||
63 | if (!attribute->show) | |
64 | return -EIO; | |
65 | ||
66 | return attribute->show(foo, attribute, buf); | |
67 | } | |
68 | ||
69 | /* | |
70 | * Just like the default show function above, but this one is for when the | |
71 | * sysfs "store" is requested (when a value is written to a file.) | |
72 | */ | |
73 | static ssize_t foo_attr_store(struct kobject *kobj, | |
74 | struct attribute *attr, | |
75 | const char *buf, size_t len) | |
76 | { | |
77 | struct foo_attribute *attribute; | |
78 | struct foo_obj *foo; | |
79 | ||
80 | attribute = to_foo_attr(attr); | |
81 | foo = to_foo_obj(kobj); | |
82 | ||
83 | if (!attribute->store) | |
84 | return -EIO; | |
85 | ||
86 | return attribute->store(foo, attribute, buf, len); | |
87 | } | |
88 | ||
89 | /* Our custom sysfs_ops that we will associate with our ktype later on */ | |
90 | static struct sysfs_ops foo_sysfs_ops = { | |
91 | .show = foo_attr_show, | |
92 | .store = foo_attr_store, | |
93 | }; | |
94 | ||
95 | /* | |
96 | * The release function for our object. This is REQUIRED by the kernel to | |
97 | * have. We free the memory held in our object here. | |
98 | * | |
99 | * NEVER try to get away with just a "blank" release function to try to be | |
100 | * smarter than the kernel. Turns out, no one ever is... | |
101 | */ | |
102 | static void foo_release(struct kobject *kobj) | |
103 | { | |
104 | struct foo_obj *foo; | |
105 | ||
106 | foo = to_foo_obj(kobj); | |
107 | kfree(foo); | |
108 | } | |
109 | ||
110 | /* | |
111 | * The "foo" file where the .foo variable is read from and written to. | |
112 | */ | |
113 | static ssize_t foo_show(struct foo_obj *foo_obj, struct foo_attribute *attr, | |
114 | char *buf) | |
115 | { | |
116 | return sprintf(buf, "%d\n", foo_obj->foo); | |
117 | } | |
118 | ||
119 | static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr, | |
120 | const char *buf, size_t count) | |
121 | { | |
122 | sscanf(buf, "%du", &foo_obj->foo); | |
123 | return count; | |
124 | } | |
125 | ||
126 | static struct foo_attribute foo_attribute = | |
127 | __ATTR(foo, 0666, foo_show, foo_store); | |
128 | ||
129 | /* | |
130 | * More complex function where we determine which varible is being accessed by | |
131 | * looking at the attribute for the "baz" and "bar" files. | |
132 | */ | |
133 | static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr, | |
134 | char *buf) | |
135 | { | |
136 | int var; | |
137 | ||
138 | if (strcmp(attr->attr.name, "baz") == 0) | |
139 | var = foo_obj->baz; | |
140 | else | |
141 | var = foo_obj->bar; | |
142 | return sprintf(buf, "%d\n", var); | |
143 | } | |
144 | ||
145 | static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr, | |
146 | const char *buf, size_t count) | |
147 | { | |
148 | int var; | |
149 | ||
150 | sscanf(buf, "%du", &var); | |
151 | if (strcmp(attr->attr.name, "baz") == 0) | |
152 | foo_obj->baz = var; | |
153 | else | |
154 | foo_obj->bar = var; | |
155 | return count; | |
156 | } | |
157 | ||
158 | static struct foo_attribute baz_attribute = | |
159 | __ATTR(baz, 0666, b_show, b_store); | |
160 | static struct foo_attribute bar_attribute = | |
161 | __ATTR(bar, 0666, b_show, b_store); | |
162 | ||
163 | /* | |
164 | * Create a group of attributes so that we can create and destory them all | |
165 | * at once. | |
166 | */ | |
167 | static struct attribute *foo_default_attrs[] = { | |
168 | &foo_attribute.attr, | |
169 | &baz_attribute.attr, | |
170 | &bar_attribute.attr, | |
171 | NULL, /* need to NULL terminate the list of attributes */ | |
172 | }; | |
173 | ||
174 | /* | |
175 | * Our own ktype for our kobjects. Here we specify our sysfs ops, the | |
176 | * release function, and the set of default attributes we want created | |
177 | * whenever a kobject of this type is registered with the kernel. | |
178 | */ | |
179 | static struct kobj_type foo_ktype = { | |
180 | .sysfs_ops = &foo_sysfs_ops, | |
181 | .release = foo_release, | |
182 | .default_attrs = foo_default_attrs, | |
183 | }; | |
184 | ||
185 | static struct kset *example_kset; | |
186 | static struct foo_obj *foo_obj; | |
187 | static struct foo_obj *bar_obj; | |
188 | static struct foo_obj *baz_obj; | |
189 | ||
190 | static struct foo_obj *create_foo_obj(const char *name) | |
191 | { | |
192 | struct foo_obj *foo; | |
193 | int retval; | |
194 | ||
195 | /* allocate the memory for the whole object */ | |
196 | foo = kzalloc(sizeof(*foo), GFP_KERNEL); | |
197 | if (!foo) | |
198 | return NULL; | |
199 | ||
200 | /* | |
201 | * As we have a kset for this kobject, we need to set it before calling | |
202 | * the kobject core. | |
203 | */ | |
204 | foo->kobj.kset = example_kset; | |
205 | ||
206 | /* | |
207 | * Initialize and add the kobject to the kernel. All the default files | |
208 | * will be created here. As we have already specified a kset for this | |
209 | * kobject, we don't have to set a parent for the kobject, the kobject | |
210 | * will be placed beneath that kset automatically. | |
211 | */ | |
212 | retval = kobject_init_and_add(&foo->kobj, &foo_ktype, NULL, "%s", name); | |
213 | if (retval) { | |
214 | kfree(foo); | |
215 | return NULL; | |
216 | } | |
217 | ||
218 | /* | |
219 | * We are always responsible for sending the uevent that the kobject | |
220 | * was added to the system. | |
221 | */ | |
222 | kobject_uevent(&foo->kobj, KOBJ_ADD); | |
223 | ||
224 | return foo; | |
225 | } | |
226 | ||
227 | static void destroy_foo_obj(struct foo_obj *foo) | |
228 | { | |
229 | kobject_put(&foo->kobj); | |
230 | } | |
231 | ||
232 | static int example_init(void) | |
233 | { | |
234 | /* | |
235 | * Create a kset with the name of "kset_example", | |
236 | * located under /sys/kernel/ | |
237 | */ | |
238 | example_kset = kset_create_and_add("kset_example", NULL, kernel_kobj); | |
239 | if (!example_kset) | |
240 | return -ENOMEM; | |
241 | ||
242 | /* | |
243 | * Create three objects and register them with our kset | |
244 | */ | |
245 | foo_obj = create_foo_obj("foo"); | |
246 | if (!foo_obj) | |
247 | goto foo_error; | |
248 | ||
249 | bar_obj = create_foo_obj("bar"); | |
250 | if (!bar_obj) | |
251 | goto bar_error; | |
252 | ||
253 | baz_obj = create_foo_obj("baz"); | |
254 | if (!baz_obj) | |
255 | goto baz_error; | |
256 | ||
257 | return 0; | |
258 | ||
259 | baz_error: | |
260 | destroy_foo_obj(bar_obj); | |
261 | bar_error: | |
262 | destroy_foo_obj(foo_obj); | |
263 | foo_error: | |
264 | return -EINVAL; | |
265 | } | |
266 | ||
267 | static void example_exit(void) | |
268 | { | |
269 | destroy_foo_obj(baz_obj); | |
270 | destroy_foo_obj(bar_obj); | |
271 | destroy_foo_obj(foo_obj); | |
272 | kset_unregister(example_kset); | |
273 | } | |
274 | ||
275 | module_init(example_init); | |
276 | module_exit(example_exit); | |
277 | MODULE_LICENSE("GPL"); | |
278 | MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>"); |