#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/string.h>

#define BUF_SIZE 1024

static char param1_buf[BUF_SIZE];

// 读取函数
static ssize_t param1_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) {
    return snprintf(buf, BUF_SIZE, "%s\n", param1_buf);
}

// 写入函数
static ssize_t param1_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) {
    if (count > BUF_SIZE)
        return -EINVAL;

    strncpy(param1_buf, buf, count);
    param1_buf[count] = '\0';

    return count;
}

// 定义一个 kobj_attribute 结构体，关联读写函数
static struct kobj_attribute param1_attribute =
    __ATTR(param1, 0664, param1_show, param1_store);

// 在 /sys/uos 下创建一个目录并注册 param1 属性
static struct attribute *attrs[] = {
    &param1_attribute.attr,
    NULL,
};

static struct attribute_group attr_group = {
    .attrs = attrs,
};

static struct kobject *uos_kobj;

static int __init uos_param_init(void) {
    int retval;

    uos_kobj = kobject_create_and_add("uos", kernel_kobj);
    if (!uos_kobj)
        return -ENOMEM;

    retval = sysfs_create_group(uos_kobj, &attr_group);
    if (retval)
        kobject_put(uos_kobj);

    return retval;
}

static void __exit uos_param_exit(void) {
    kobject_put(uos_kobj);
}

module_init(uos_param_init);
module_exit(uos_param_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Longji Guo");

obj-m += sysfs_example.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean