C语言学习

/*
 * kset and ktype example
 */
#include <linux/kobject.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/ks_a
 */


/*
 * This is our "object" that we will create a few of and register them with
 * sysfs.
 */
struct fu_obj {
    struct kobject kobj;
    int par;
};
#define to_fu_obj(x) container_of(x, struct fu_obj, kobj)

/*
 * 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 fu_release(struct kobject *kobj)
{
    struct fu_obj *fu;

    fu = to_fu_obj(kobj);
    kfree(fu);
}

/*
 * Our own ktype for our kobjects.  Here we only specify the
 * release function.
 */
static struct kobj_type fu_ktype = { 
    .release = fu_release,
};

static struct kset *ks_a;
static struct fu_obj *fu_a1;
static struct fu_obj *fu_a2;
static struct fu_obj *fu_a3;

static struct fu_obj *create_fu_obj(const char *name)
{
    struct fu_obj *fu;
    int retval;

    /* allocate the memory for the whole object */
    fu = kzalloc(sizeof(*fu), GFP_KERNEL);
    if (!fu)
        return NULL;

    /*
     * As we have a kset for this kobject, we need to set it before calling
     * the kobject core.
     */
    fu->kobj.kset = ks_a;

    /*
     * 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(&fu->kobj, &fu_ktype, NULL, "%s", name);
    if (retval) {
        kobject_put(&fu->kobj);
        return NULL;
    }

    return fu;
}

static void destroy_fu_obj(struct fu_obj *fu)
{
    kobject_put(&fu->kobj);
}

static int __init example_init(void)
{
    /*
     * Create a kset with the name of "ks_a",
     * located under /sys/kernel/
     */
    ks_a = kset_create_and_add("ks_a", NULL, kernel_kobj);
    if (!ks_a)
        return -ENOMEM;

    /*
     * Create three objects and register them with our kset
     */
    fu_a1 = create_fu_obj("fu_a1");
    if (!fu_a1)
        goto err_fu_a1;

    fu_a2 = create_fu_obj("fu_a2");
    if (!fu_a2)
        goto err_fu_a2;

    fu_a3 = create_fu_obj("fu_a3");
    if (!fu_a3)
        goto err_fu_a3;

    return 0;

err_fu_a3:
    destroy_fu_obj(fu_a2);
err_fu_a2:
    destroy_fu_obj(fu_a1);
err_fu_a1:
    kset_unregister(ks_a);
    return -EINVAL;
}

static void __exit example_exit(void)
{
    destroy_fu_obj(fu_a3);
    destroy_fu_obj(fu_a2);
    destroy_fu_obj(fu_a1);
    kset_unregister(ks_a);
}

module_init(example_init);
module_exit(example_exit);
MODULE_LICENSE("GPL");