list_head sample

listtest.c

#include <linux/module.h>       /* MODULE, THIS_MODULE */
#include <linux/moduleparam.h>
#include <linux/kernel.h>       /* printk() */
#include <linux/errno.h>	/* error codes */
#include <linux/list.h>         /* list_*() */
#include <linux/slab.h>         /* kmalloc() */

MODULE_AUTHOR("Masayuki Ito");
MODULE_LICENSE("Dual BSD/GPL");

#ifndef LISTTEST_NR_DEVS
#define LISTTEST_NR_DEVS 4 /* マイナーデバイス番号の総数 */
#endif

#ifndef DRIVER_NAME
#define DRIVER_NAME "hello"
#endif

int listtest_major = 0;
int listtest_minor = 0;
int listtest_nr_devs = LISTTEST_NR_DEVS;

struct test_data
{
        int no;
        struct list_head list;
};

struct test_data head = {
        .no = -1,
};

#if 0
static void listtest_push_no(int no)
{
        struct test_data *new_data;
        new_data = kmalloc(sizeof(struct test_data), GFP_KERNEL);
        if(new_data) {
                new_data->no = no;
                list_add(&new_data->list, &head.list);
        }
}
#endif

static void listtest_show_list(void)
{
        struct list_head *listptr;
        struct test_data *entry;
        printk(KERN_ALERT "show_list\n");
        
        printk(KERN_ALERT "no = %d (list %p, prev = %p, next = %p)\n", 
               head.no, &head.list, head.list.prev, head.list.next);

        list_for_each(listptr, &head.list) {
                entry = list_entry(listptr, struct test_data, list);
                printk(KERN_ALERT "no = %d (list %p, prev = %p, next = %p)\n", 
                       entry->no, &entry->list, entry->list.prev, entry->list.next);
        }
}

#if 0
static void listtest_pop(void)
{
        struct test_data *ptr;
        ptr = list_entry(head.list.next, struct test_data, list);
        list_del(head.list.next);
        kfree(ptr);
}
#endif

static int listtest_init(void)
{
        struct test_data *ptr;
        struct test_data *new_data;

        INIT_LIST_HEAD(&head.list);
        listtest_show_list();

        new_data = kmalloc(sizeof(struct test_data), GFP_KERNEL);
        new_data->no = 1;
        list_add(&new_data->list, &head.list);
        listtest_show_list();

        ptr = list_entry(head.list.next, struct test_data, list);
        list_del(head.list.next);

        listtest_show_list();

        kfree(ptr);
        return 0;
}

#if 0
static int listtest_init(void)
{
        int i;
        printk(KERN_ALERT "Listtest init\n");
        INIT_LIST_HEAD(&head.list);

        for(i = 0; i < 3; ++i) {
                listtest_push_no(i);
                listtest_show_list();
        }

        for(i = 0; i < 3; ++i) {
                listtest_pop();
                listtest_show_list();
        }

        return 0;
}
#endif

static void listtest_exit(void)
{
        printk(KERN_ALERT "Listtest exit\n");
}

module_init(listtest_init);
module_exit(listtest_exit);

Makefile

obj-m := listtest.o

INC  := /usr/src/kernels/3.4.0-1.fc17.x86_64/include
KDIR := /lib/modules/$(shell uname -r)/build
PWD  := $(shell pwd)

default:
	$(MAKE) -C $(KDIR) M=$(PWD) modules

check-syntax:
	$(MAKE) -C $(KDIR) M=$(PWD) modules

clean:
	$(MAKE) -C $(KDIR) M=$(PWD) modules clean