mirror of https://gitee.com/openkylin/linux.git
147 lines
3.4 KiB
C
147 lines
3.4 KiB
C
/*
|
|
* Sample kobject implementation
|
|
*
|
|
* Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com>
|
|
* Copyright (C) 2007 Novell Inc.
|
|
*
|
|
* Released under the GPL version 2 only.
|
|
*
|
|
*/
|
|
#include <linux/kobject.h>
|
|
#include <linux/string.h>
|
|
#include <linux/sysfs.h>
|
|
#include <linux/module.h>
|
|
#include <linux/init.h>
|
|
|
|
/*
|
|
* This module shows how to create a simple subdirectory in sysfs called
|
|
* /sys/kernel/kobject-example In that directory, 3 files are created:
|
|
* "foo", "baz", and "bar". If an integer is written to these files, it can be
|
|
* later read out of it.
|
|
*/
|
|
|
|
static int foo;
|
|
static int baz;
|
|
static int bar;
|
|
|
|
/*
|
|
* The "foo" file where a static variable is read from and written to.
|
|
*/
|
|
static ssize_t foo_show(struct kobject *kobj, struct kobj_attribute *attr,
|
|
char *buf)
|
|
{
|
|
return sprintf(buf, "%d\n", foo);
|
|
}
|
|
|
|
static ssize_t foo_store(struct kobject *kobj, struct kobj_attribute *attr,
|
|
const char *buf, size_t count)
|
|
{
|
|
int ret;
|
|
|
|
ret = kstrtoint(buf, 10, &foo);
|
|
if (ret < 0)
|
|
return ret;
|
|
|
|
return count;
|
|
}
|
|
|
|
/* Sysfs attributes cannot be world-writable. */
|
|
static struct kobj_attribute foo_attribute =
|
|
__ATTR(foo, 0664, foo_show, foo_store);
|
|
|
|
/*
|
|
* More complex function where we determine which variable is being accessed by
|
|
* looking at the attribute for the "baz" and "bar" files.
|
|
*/
|
|
static ssize_t b_show(struct kobject *kobj, struct kobj_attribute *attr,
|
|
char *buf)
|
|
{
|
|
int var;
|
|
|
|
if (strcmp(attr->attr.name, "baz") == 0)
|
|
var = baz;
|
|
else
|
|
var = bar;
|
|
return sprintf(buf, "%d\n", var);
|
|
}
|
|
|
|
static ssize_t b_store(struct kobject *kobj, struct kobj_attribute *attr,
|
|
const char *buf, size_t count)
|
|
{
|
|
int var, ret;
|
|
|
|
ret = kstrtoint(buf, 10, &var);
|
|
if (ret < 0)
|
|
return ret;
|
|
|
|
if (strcmp(attr->attr.name, "baz") == 0)
|
|
baz = var;
|
|
else
|
|
bar = var;
|
|
return count;
|
|
}
|
|
|
|
static struct kobj_attribute baz_attribute =
|
|
__ATTR(baz, 0664, b_show, b_store);
|
|
static struct kobj_attribute bar_attribute =
|
|
__ATTR(bar, 0664, b_show, b_store);
|
|
|
|
|
|
/*
|
|
* Create a group of attributes so that we can create and destroy them all
|
|
* at once.
|
|
*/
|
|
static struct attribute *attrs[] = {
|
|
&foo_attribute.attr,
|
|
&baz_attribute.attr,
|
|
&bar_attribute.attr,
|
|
NULL, /* need to NULL terminate the list of attributes */
|
|
};
|
|
|
|
/*
|
|
* An unnamed attribute group will put all of the attributes directly in
|
|
* the kobject directory. If we specify a name, a subdirectory will be
|
|
* created for the attributes with the directory being the name of the
|
|
* attribute group.
|
|
*/
|
|
static struct attribute_group attr_group = {
|
|
.attrs = attrs,
|
|
};
|
|
|
|
static struct kobject *example_kobj;
|
|
|
|
static int __init example_init(void)
|
|
{
|
|
int retval;
|
|
|
|
/*
|
|
* Create a simple kobject with the name of "kobject_example",
|
|
* located under /sys/kernel/
|
|
*
|
|
* As this is a simple directory, no uevent will be sent to
|
|
* userspace. That is why this function should not be used for
|
|
* any type of dynamic kobjects, where the name and number are
|
|
* not known ahead of time.
|
|
*/
|
|
example_kobj = kobject_create_and_add("kobject_example", kernel_kobj);
|
|
if (!example_kobj)
|
|
return -ENOMEM;
|
|
|
|
/* Create the files associated with this kobject */
|
|
retval = sysfs_create_group(example_kobj, &attr_group);
|
|
if (retval)
|
|
kobject_put(example_kobj);
|
|
|
|
return retval;
|
|
}
|
|
|
|
static void __exit example_exit(void)
|
|
{
|
|
kobject_put(example_kobj);
|
|
}
|
|
|
|
module_init(example_init);
|
|
module_exit(example_exit);
|
|
MODULE_LICENSE("GPL v2");
|
|
MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");
|