Orange Pi5 kernel

// SPDX-License-Identifier: GPL-2.0
/*
 * Sample kset and ktype implementation
 *
 * Copyright (C) 2004-2007 Greg Kroah-Hartman <greg@kroah.com>
 * Copyright (C) 2007 Novell Inc.
 */
#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);
}
 
/*
 * 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);
}
 
/* 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);
}
 
/*
 * 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);
}
 
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;
}
 
/* 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->attr.name, "baz") == 0)
<------><------>var = foo_obj->baz;
<------>else
<------><------>var = foo_obj->bar;
<------>return sprintf(buf, "%d\n", var);
}
 
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->attr.name, "baz") == 0)
<------><------>foo_obj->baz = var;
<------>else
<------><------>foo_obj->bar = var;
<------>return count;
}
 
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 */
};
ATTRIBUTE_GROUPS(foo_default);
 
/*
 * 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_groups = foo_default_groups,
};
 
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;
}
 
static void destroy_foo_obj(struct foo_obj *foo)
{
<------>kobject_put(&foo->kobj);
}
 
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;
}
 
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);
}
 
module_init(example_init);
module_exit(example_exit);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Greg Kroah-Hartman <greg@kroah.com>");