? 此文件是在/sys/kernel/目錄里面建立三個文件foo、baz、bar，每個文件都是靜態(tài)的int型的緩存空間。

可以在這三個文件中讀寫一些整形的數(shù)據(jù)。

/*
?* ?* 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)
{
sscanf(buf, "%du", &foo);
return count;
}




static struct kobj_attribute foo_attribute = __ATTR(foo, 0666, 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;
sscanf(buf, "%du", &var);
if (strcmp(attr->attr.name, "baz") == 0)
baz = var;
else
bar = var;
return count;
}




static struct kobj_attribute baz_attribute = __ATTR(baz, 0666, b_show, b_store);
static struct kobj_attribute bar_attribute = __ATTR(bar, 0666, 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");
MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");

Makefile:

obj-m = systest.o


K_DIR = $(shell uname -r)
PWD = $(shell pwd)


all:
make -C /lib/modules/$(K_DIR)/build M=$(PWD) modules
clean:
make -C /lib/modules/$(K_DIR)/build M=$(PWD) clean

測試：

root@qinrenzhi-G31M-ES2C:/home/qinrenzhi/private/driver/sys# insmod systest.ko

root@qinrenzhi-G31M-ES2C:/home/qinrenzhi/private/driver/sys# cd /sys/kernel/kobject_example/

root@qinrenzhi-G31M-ES2C:/sys/kernel/kobject_example# ls
bar ?baz ?foo
root@qinrenzhi-G31M-ES2C:/sys/kernel/kobject_example# cat bar
1234
root@qinrenzhi-G31M-ES2C:/sys/kernel/kobject_example# echo 8888 > bar
root@qinrenzhi-G31M-ES2C:/sys/kernel/kobject_example# cat bar
8888

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