cregit-Linux how code gets into the kernel

Release 4.7 samples/kobject/kset-example.c

Directory: samples/kobject
 * Sample kset and ktype implementation
 * Copyright (C) 2004-2007 Greg Kroah-Hartman <>
 * 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/slab.h>
#include <linux/module.h>
#include <linux/init.h>

 * This module shows how to create a kset in sysfs called
 * /sys/kernel/kset-example
 * Then tree kobjects are created and assigned to this kset, "foo", "baz",
 * and "bar".  In those kobjects, attributes of the same name are also
 * created and if an integer is written to these files, it can be later
 * read out of it.

 * This is our "object" that we will create a few of and register them with
 * sysfs.

struct foo_obj {
struct kobject kobj;
int foo;
int baz;
int bar;

#define to_foo_obj(x) container_of(x, struct foo_obj, kobj)

/* a custom attribute that works just for a struct foo_obj. */

struct foo_attribute {
struct attribute attr;
ssize_t (*show)(struct foo_obj *foo, struct foo_attribute *attr, char *buf);
ssize_t (*store)(struct foo_obj *foo, struct foo_attribute *attr, const char *buf, size_t count);

#define to_foo_attr(x) container_of(x, struct foo_attribute, attr)

 * The default show function that must be passed to sysfs.  This will be
 * called by sysfs for whenever a show function is called by the user on a
 * sysfs file associated with the kobjects we have registered.  We need to
 * transpose back from a "default" kobject to our custom struct foo_obj and
 * then call the show function for that specific object.

static ssize_t foo_attr_show(struct kobject *kobj, struct attribute *attr, char *buf) { struct foo_attribute *attribute; struct foo_obj *foo; attribute = to_foo_attr(attr); foo = to_foo_obj(kobj); if (!attribute->show) return -EIO; return attribute->show(foo, attribute, buf); }


greg kroah-hartmangreg kroah-hartman67100.00%1100.00%

/* * Just like the default show function above, but this one is for when the * sysfs "store" is requested (when a value is written to a file.) */
static ssize_t foo_attr_store(struct kobject *kobj, struct attribute *attr, const char *buf, size_t len) { struct foo_attribute *attribute; struct foo_obj *foo; attribute = to_foo_attr(attr); foo = to_foo_obj(kobj); if (!attribute->store) return -EIO; return attribute->store(foo, attribute, buf, len); }


greg kroah-hartmangreg kroah-hartman73100.00%1100.00%

/* Our custom sysfs_ops that we will associate with our ktype later on */ static const struct sysfs_ops foo_sysfs_ops = { .show = foo_attr_show, .store = foo_attr_store, }; /* * The release function for our object. This is REQUIRED by the kernel to * have. We free the memory held in our object here. * * NEVER try to get away with just a "blank" release function to try to be * smarter than the kernel. Turns out, no one ever is... */
static void foo_release(struct kobject *kobj) { struct foo_obj *foo; foo = to_foo_obj(kobj); kfree(foo); }


greg kroah-hartmangreg kroah-hartman28100.00%1100.00%

/* * The "foo" file where the .foo variable is read from and written to. */
static ssize_t foo_show(struct foo_obj *foo_obj, struct foo_attribute *attr, char *buf) { return sprintf(buf, "%d\n", foo_obj->foo); }


greg kroah-hartmangreg kroah-hartman32100.00%1100.00%

static ssize_t foo_store(struct foo_obj *foo_obj, struct foo_attribute *attr, const char *buf, size_t count) { int ret; ret = kstrtoint(buf, 10, &foo_obj->foo); if (ret < 0) return ret; return count; }


greg kroah-hartmangreg kroah-hartman3769.81%150.00%
rastislav barlikrastislav barlik1630.19%150.00%

/* Sysfs attributes cannot be world-writable. */ static struct foo_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 foo_obj *foo_obj, struct foo_attribute *attr, char *buf) { int var; if (strcmp(attr->, "baz") == 0) var = foo_obj->baz; else var = foo_obj->bar; return sprintf(buf, "%d\n", var); }


greg kroah-hartmangreg kroah-hartman61100.00%1100.00%

static ssize_t b_store(struct foo_obj *foo_obj, struct foo_attribute *attr, const char *buf, size_t count) { int var, ret; ret = kstrtoint(buf, 10, &var); if (ret < 0) return ret; if (strcmp(attr->, "baz") == 0) foo_obj->baz = var; else foo_obj->bar = var; return count; }


greg kroah-hartmangreg kroah-hartman6681.48%150.00%
rastislav barlikrastislav barlik1518.52%150.00%

static struct foo_attribute baz_attribute = __ATTR(baz, 0664, b_show, b_store); static struct foo_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 *foo_default_attrs[] = { &foo_attribute.attr, &baz_attribute.attr, &bar_attribute.attr, NULL, /* need to NULL terminate the list of attributes */ }; /* * Our own ktype for our kobjects. Here we specify our sysfs ops, the * release function, and the set of default attributes we want created * whenever a kobject of this type is registered with the kernel. */ static struct kobj_type foo_ktype = { .sysfs_ops = &foo_sysfs_ops, .release = foo_release, .default_attrs = foo_default_attrs, }; static struct kset *example_kset; static struct foo_obj *foo_obj; static struct foo_obj *bar_obj; static struct foo_obj *baz_obj;
static struct foo_obj *create_foo_obj(const char *name) { struct foo_obj *foo; int retval; /* allocate the memory for the whole object */ foo = kzalloc(sizeof(*foo), GFP_KERNEL); if (!foo) return NULL; /* * As we have a kset for this kobject, we need to set it before calling * the kobject core. */ foo->kobj.kset = example_kset; /* * Initialize and add the kobject to the kernel. All the default files * will be created here. As we have already specified a kset for this * kobject, we don't have to set a parent for the kobject, the kobject * will be placed beneath that kset automatically. */ retval = kobject_init_and_add(&foo->kobj, &foo_ktype, NULL, "%s", name); if (retval) { kobject_put(&foo->kobj); return NULL; } /* * We are always responsible for sending the uevent that the kobject * was added to the system. */ kobject_uevent(&foo->kobj, KOBJ_ADD); return foo; }


greg kroah-hartmangreg kroah-hartman9996.12%150.00%
li zefanli zefan43.88%150.00%

static void destroy_foo_obj(struct foo_obj *foo) { kobject_put(&foo->kobj); }


greg kroah-hartmangreg kroah-hartman19100.00%1100.00%

static int __init example_init(void) { /* * Create a kset with the name of "kset_example", * located under /sys/kernel/ */ example_kset = kset_create_and_add("kset_example", NULL, kernel_kobj); if (!example_kset) return -ENOMEM; /* * Create three objects and register them with our kset */ foo_obj = create_foo_obj("foo"); if (!foo_obj) goto foo_error; bar_obj = create_foo_obj("bar"); if (!bar_obj) goto bar_error; baz_obj = create_foo_obj("baz"); if (!baz_obj) goto baz_error; return 0; baz_error: destroy_foo_obj(bar_obj); bar_error: destroy_foo_obj(foo_obj); foo_error: kset_unregister(example_kset); return -EINVAL; }


greg kroah-hartmangreg kroah-hartman9894.23%133.33%
bjorn helgaasbjorn helgaas54.81%133.33%
qinghuang fengqinghuang feng10.96%133.33%

static void __exit example_exit(void) { destroy_foo_obj(baz_obj); destroy_foo_obj(bar_obj); destroy_foo_obj(foo_obj); kset_unregister(example_kset); }


greg kroah-hartmangreg kroah-hartman2896.55%150.00%
qinghuang fengqinghuang feng13.45%150.00%

module_init(example_init); module_exit(example_exit); MODULE_LICENSE("GPL v2"); MODULE_AUTHOR("Greg Kroah-Hartman <>");

Overall Contributors

greg kroah-hartmangreg kroah-hartman87794.40%220.00%
rastislav barlikrastislav barlik313.34%110.00%
bjorn helgaasbjorn helgaas50.54%110.00%
rusty russellrusty russell40.43%110.00%
li zefanli zefan40.43%110.00%
tejun heotejun heo30.32%110.00%
qinghuang fengqinghuang feng20.22%110.00%
radu voicilasradu voicilas20.22%110.00%
emese revfyemese revfy10.11%110.00%
Directory: samples/kobject
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