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![Greg Kroah-Hartman](/assets/img/avatar_default.png)
Now that the SPDX tag is in all kobject files, that identifies the license in a specific and legally-defined manner. So the extra GPL text wording can be removed as it is no longer needed at all. This is done on a quest to remove the 700+ different ways that files in the kernel describe the GPL license text. And there's unneeded stuff like the address (sometimes incorrect) for the FSF which is never needed. No copyright headers or other non-license-description text was removed. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
287 lines
6.9 KiB
C
287 lines
6.9 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Sample kset and ktype implementation
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*
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* Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com>
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* Copyright (C) 2007 Novell Inc.
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*/
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#include <linux/kobject.h>
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#include <linux/string.h>
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#include <linux/sysfs.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/init.h>
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/*
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* This module shows how to create a kset in sysfs called
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* /sys/kernel/kset-example
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* Then tree kobjects are created and assigned to this kset, "foo", "baz",
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* and "bar". In those kobjects, attributes of the same name are also
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* created and if an integer is written to these files, it can be later
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* read out of it.
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*/
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/*
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* This is our "object" that we will create a few of and register them with
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* sysfs.
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*/
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struct foo_obj {
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struct kobject kobj;
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int foo;
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int baz;
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int bar;
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};
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#define to_foo_obj(x) container_of(x, struct foo_obj, kobj)
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/* a custom attribute that works just for a struct foo_obj. */
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struct foo_attribute {
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struct attribute attr;
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ssize_t (*show)(struct foo_obj *foo, struct foo_attribute *attr, char *buf);
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ssize_t (*store)(struct foo_obj *foo, struct foo_attribute *attr, const char *buf, size_t count);
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};
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#define to_foo_attr(x) container_of(x, struct foo_attribute, attr)
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/*
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* The default show function that must be passed to sysfs. This will be
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* called by sysfs for whenever a show function is called by the user on a
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* sysfs file associated with the kobjects we have registered. We need to
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* transpose back from a "default" kobject to our custom struct foo_obj and
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* then call the show function for that specific object.
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*/
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static ssize_t foo_attr_show(struct kobject *kobj,
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struct attribute *attr,
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char *buf)
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{
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struct foo_attribute *attribute;
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struct foo_obj *foo;
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attribute = to_foo_attr(attr);
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foo = to_foo_obj(kobj);
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if (!attribute->show)
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return -EIO;
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return attribute->show(foo, attribute, buf);
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}
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/*
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* Just like the default show function above, but this one is for when the
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* sysfs "store" is requested (when a value is written to a file.)
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*/
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static ssize_t foo_attr_store(struct kobject *kobj,
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struct attribute *attr,
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const char *buf, size_t len)
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{
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struct foo_attribute *attribute;
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struct foo_obj *foo;
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attribute = to_foo_attr(attr);
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foo = to_foo_obj(kobj);
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if (!attribute->store)
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return -EIO;
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return attribute->store(foo, attribute, buf, len);
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}
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/* Our custom sysfs_ops that we will associate with our ktype later on */
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static const struct sysfs_ops foo_sysfs_ops = {
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.show = foo_attr_show,
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.store = foo_attr_store,
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};
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/*
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* The release function for our object. This is REQUIRED by the kernel to
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* have. We free the memory held in our object here.
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*
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* NEVER try to get away with just a "blank" release function to try to be
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* smarter than the kernel. Turns out, no one ever is...
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*/
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static void foo_release(struct kobject *kobj)
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{
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struct foo_obj *foo;
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foo = to_foo_obj(kobj);
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kfree(foo);
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}
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/*
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* The "foo" file where the .foo variable is read from and written to.
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*/
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static ssize_t foo_show(struct foo_obj *foo_obj, struct foo_attribute *attr,
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char *buf)
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{
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return sprintf(buf, "%d\n", foo_obj->foo);
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}
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static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr,
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const char *buf, size_t count)
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{
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int ret;
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ret = kstrtoint(buf, 10, &foo_obj->foo);
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if (ret < 0)
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return ret;
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return count;
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}
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/* Sysfs attributes cannot be world-writable. */
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static struct foo_attribute foo_attribute =
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__ATTR(foo, 0664, foo_show, foo_store);
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/*
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* More complex function where we determine which variable is being accessed by
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* looking at the attribute for the "baz" and "bar" files.
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*/
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static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr,
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char *buf)
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{
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int var;
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if (strcmp(attr->attr.name, "baz") == 0)
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var = foo_obj->baz;
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else
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var = foo_obj->bar;
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return sprintf(buf, "%d\n", var);
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}
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static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr,
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const char *buf, size_t count)
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{
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int var, ret;
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ret = kstrtoint(buf, 10, &var);
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if (ret < 0)
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return ret;
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if (strcmp(attr->attr.name, "baz") == 0)
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foo_obj->baz = var;
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else
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foo_obj->bar = var;
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return count;
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}
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static struct foo_attribute baz_attribute =
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__ATTR(baz, 0664, b_show, b_store);
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static struct foo_attribute bar_attribute =
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__ATTR(bar, 0664, b_show, b_store);
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/*
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* Create a group of attributes so that we can create and destroy them all
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* at once.
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*/
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static struct attribute *foo_default_attrs[] = {
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&foo_attribute.attr,
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&baz_attribute.attr,
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&bar_attribute.attr,
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NULL, /* need to NULL terminate the list of attributes */
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};
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/*
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* Our own ktype for our kobjects. Here we specify our sysfs ops, the
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* release function, and the set of default attributes we want created
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* whenever a kobject of this type is registered with the kernel.
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*/
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static struct kobj_type foo_ktype = {
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.sysfs_ops = &foo_sysfs_ops,
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.release = foo_release,
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.default_attrs = foo_default_attrs,
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};
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static struct kset *example_kset;
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static struct foo_obj *foo_obj;
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static struct foo_obj *bar_obj;
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static struct foo_obj *baz_obj;
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static struct foo_obj *create_foo_obj(const char *name)
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{
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struct foo_obj *foo;
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int retval;
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/* allocate the memory for the whole object */
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foo = kzalloc(sizeof(*foo), GFP_KERNEL);
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if (!foo)
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return NULL;
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/*
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* As we have a kset for this kobject, we need to set it before calling
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* the kobject core.
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*/
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foo->kobj.kset = example_kset;
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/*
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* Initialize and add the kobject to the kernel. All the default files
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* will be created here. As we have already specified a kset for this
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* kobject, we don't have to set a parent for the kobject, the kobject
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* will be placed beneath that kset automatically.
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*/
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retval = kobject_init_and_add(&foo->kobj, &foo_ktype, NULL, "%s", name);
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if (retval) {
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kobject_put(&foo->kobj);
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return NULL;
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}
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/*
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* We are always responsible for sending the uevent that the kobject
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* was added to the system.
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*/
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kobject_uevent(&foo->kobj, KOBJ_ADD);
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return foo;
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}
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static void destroy_foo_obj(struct foo_obj *foo)
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{
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kobject_put(&foo->kobj);
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}
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static int __init example_init(void)
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{
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/*
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* Create a kset with the name of "kset_example",
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* located under /sys/kernel/
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*/
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example_kset = kset_create_and_add("kset_example", NULL, kernel_kobj);
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if (!example_kset)
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return -ENOMEM;
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/*
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* Create three objects and register them with our kset
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*/
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foo_obj = create_foo_obj("foo");
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if (!foo_obj)
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goto foo_error;
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bar_obj = create_foo_obj("bar");
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if (!bar_obj)
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goto bar_error;
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baz_obj = create_foo_obj("baz");
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if (!baz_obj)
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goto baz_error;
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return 0;
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baz_error:
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destroy_foo_obj(bar_obj);
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bar_error:
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destroy_foo_obj(foo_obj);
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foo_error:
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kset_unregister(example_kset);
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return -EINVAL;
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}
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static void __exit example_exit(void)
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{
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destroy_foo_obj(baz_obj);
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destroy_foo_obj(bar_obj);
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destroy_foo_obj(foo_obj);
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kset_unregister(example_kset);
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}
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module_init(example_init);
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module_exit(example_exit);
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MODULE_LICENSE("GPL v2");
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MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");
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