Linux Driver 入门-1

first_cdev_module.c :

#include <linux/init.h>

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/device.h>

MODULE_LICENSE("GPL");

static dev_t dev_id;
static struct cdev *my_cdev;
static struct class *first_drv_class;
static struct device *first_drv_class_device;


static ssize_t first_cdrv_read (struct file * file, char __user * buf, size_t count, loff_t *offset)
{
    printk(KERN_ALERT"first_cdrv_read start.\n");
    return 0;  
}

static ssize_t first_cdrv_write (struct file * file, const char __user * buf, size_t count, loff_t *offset)
{
    printk(KERN_ALERT"first_cdrv_write start.\n");
    return 0;  
}

static int first_cdrv_release (struct inode * inode, struct file * file)
{
    printk(KERN_ALERT"first_cdrv_release releasing.\n");
    return 0;
}

static int first_cdrv_open (struct inode * inode, struct file * file)
{
    printk(KERN_ALERT"first_cdrv_open start.\n");
    return 0;  
}

struct file_operations fops ={
    .owner = THIS_MODULE,
    .open = first_cdrv_open,
    .read = first_cdrv_read,
    .write = first_cdrv_write,
    .release = first_cdrv_release,
};

static int __init first_cdrv_init(void)
{
    int ret = 0;
    ret = alloc_chrdev_region(&dev_id, 0, 4, "first_cdrv_one");
    if(ret != 0)
    {
        printk(KERN_ERR"alloc_chrdev_region failed\n");  
    }

    my_cdev = cdev_alloc();
    cdev_init(my_cdev, &fops);
    my_cdev->owner = THIS_MODULE;

    ret = cdev_add(my_cdev, dev_id, 4);
    if(ret != 0)
    {
        printk(KERN_ERR"cdev_add failed\n");  
    }

    first_drv_class = class_create(THIS_MODULE, "first_drv");
    first_drv_class_device = device_create(first_drv_class, NULL, dev_id, NULL, "chenjun");
    
    return 0;
}

static void __exit first_cdrv_exit(void)
{
    device_destroy(first_drv_class, dev_id);
    class_destroy(first_drv_class);
    cdev_del(my_cdev);
    if(my_cdev)
    {
        printk(KERN_ALERT"kzfree\n");
        kzfree(my_cdev);
        my_cdev = NULL;
    }
    unregister_chrdev_region(dev_id, 4);
}

module_init(first_cdrv_init);

module_exit(first_cdrv_exit);

Makefile :

KERNELDIR := /opt/wfe/linux-3.2_m
PWD := $(shell pwd)
#obj-m := hello_world.o
obj-m := first_cdev_module.o
COMPILE_GCC := arm-linux-gcc

TEST := test
TEST_FILE := module_test.c

CLEAN_FILES := *.mod.* *.symvers *.order *.o *.ko $(TEST)

M_CFLAGS := -Os -Wall -g -c

default:
    make -C $(KERNELDIR) M=$(PWD) modules

$(TEST):$(TEST_FILE)
    $(COMPILE_GCC) -o $@ $<
.PHONY:clean
clean:
    rm -rf $(CLEAN_FILES)