linux 驱动入门2

不吃苦中苦，难为人上人。努力，给老婆孩子提供个良好的生活居住环境。

http://www.cnblogs.com/nan-jing/articles/5775038.html

这里提到。有这么多牛人。如果比得上人家。自古华山一条路，没别的招，不断的理解，不断的读，不断的写。哎。白了头。
阳痿早泄性无能，尿频尿急尿不净。钱不没挣多少。一身病。

上文可以完整的通过mknod创了设备节点。哪我如何知道设备号呢。
通过cat /proc/devices可以看到你创建设备的主设备号。好，没问题，可以读写了，哪我也没看到linux里有多少mknod啊。莫非是能自动创建设备节点？ 哎，是的。可以在驱动代码里创建设备节点。

这句话不完全对。是可以在驱动里写代码。让用户空间的应用创建设备节点。哪个应用？ mdev. 哪我如何通知mdev创建设备节点呢？
用着两句
class_create();
device_create();

注意测试环境，我的环境virtualbox + ubuntu16.04
好了。看代码。把上面的代码修改下。具体就修改一个函数就好了。
下面把我的测试代码发出来把
#include<linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
//#include <asm/system.h>
#include <asm/uaccess.h>
#include <linux/slab.h>
#include <linux/device.h>

MODULE_AUTHOR("qcom.shanghai@gmail.com");
MODULE_LICENSE("Dual BSD/GPL");

#define GLOBALMEM_SIZE 0X1000
#define MEM_CLEAR 0x1

static int globalmem_major = 0;

struct globalmem_dev{
struct cdev cdev;
unsigned char mem[GLOBALMEM_SIZE];
};

struct globalmem_dev *globalmem_devp;

struct class *globalmem_class;

static int globalmem_open(struct inode *inode, struct file *filp){
struct globalmem_dev *dev;
dev = container_of(inode->i_cdev, struct globalmem_dev, cdev);
filp->private_data = dev;
printk(KERN_ALERT "globalmem_open!");
return 0;
}

static int globalmem_release(struct inode *inode, struct file *filp){
printk(KERN_ALERT "globalmem_release!");
return 0;
}

static ssize_t globalmem_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos){
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
struct globalmem_dev *dev = filp->private_data;

if (p >= GLOBALMEM_SIZE){
return 0;
}
if (count > GLOBALMEM_SIZE - p){

//honeywell 臧春杰
count = GLOBALMEM_SIZE - p;
}

if (copy_to_user(buf, (void *)(dev->mem + p), count)){
ret = - EFAULT;
}else {
*ppos += count;
ret = count;
printk(KERN_ALERT "read %u bytes from %lu \n", count, p);
}
return ret;
}

static ssize_t globalmem_write(struct file *filp, const char __user *buf, size_t size, loff_t *ppos){
unsigned long p = *ppos;
unsigned int count = size;

int ret = 0;
struct globalmem_dev *dev = filp->private_data;

if (p >= GLOBALMEM_SIZE){
return 0;
}

if (count > GLOBALMEM_SIZE - p){
count = GLOBALMEM_SIZE - p;
}
if (copy_from_user(dev->mem + p, buf, count)){
ret = - EFAULT;
}else {
*ppos += count;
ret = count;
printk(KERN_ALERT "write %u bytes from %lu \n", count, p);
}

return ret;
}

static loff_t globalmem_llseek(struct file *filp, loff_t offset, int orig){
loff_t ret = 0;
switch(orig){
case 0:
if (offset < 0){
ret = - EFAULT;
break;
}
if ((unsigned int)offset > GLOBALMEM_SIZE){
ret = - EFAULT;
break;
}
filp->f_pos = (unsigned int) offset;
ret = filp->f_pos;
break;

case 1:
if ((filp->f_pos + offset) > GLOBALMEM_SIZE){
ret = - EFAULT;
break;
}

if ((filp->f_pos + offset) < 0){
ret = - EFAULT;
break;
}
filp->f_pos += offset;
ret = filp->f_pos;
break;

default:
ret = - EFAULT;
break;
}

return ret;

}

static long globalmem_ioctl(struct file *flip, unsigned int cmd, unsigned long arg){
printk(KERN_ALERT "globalmem_ioctl");
return 10L;
}

static const struct file_operations globalmem_fops = {
.owner = THIS_MODULE,
.llseek = globalmem_llseek,
.read = globalmem_read,
.write = globalmem_write,
.unlocked_ioctl = globalmem_ioctl,
.open = globalmem_open,
.release = globalmem_release,
};

static void globalmem_setup_cdev(struct globalmem_dev *dev, int index){
int err, devno = MKDEV(globalmem_major, index);
cdev_init(&(dev->cdev), &globalmem_fops);
dev->cdev.owner = THIS_MODULE;
err = cdev_add(&dev->cdev, devno, 1);
if (err){
printk(KERN_ALERT"cdev_add failed!");
}
}

//honeywell 臧春杰
static void create_dev_node(int index){
device_create(globalmem_class, NULL, MKDEV(globalmem_major, index), NULL, "globalmem_cj1");

//honeywell 臧春杰
device_create(globalmem_class, NULL, MKDEV(globalmem_major, index + 1), NULL, "globalmem_cj2");
}

static int __init globalmem_init(void){
int result;
dev_t devno = MKDEV(globalmem_major, 0);
if (globalmem_major){
result = register_chrdev_region(devno, 2, "globalmem");
}else {
result = alloc_chrdev_region(&devno,0, 2, "globalmem");
globalmem_major = MAJOR(devno);
}
printk(KERN_ALERT "major-------------->%d \n", globalmem_major);
if (result < 0){
return result;
}

//honeywell 臧春杰

globalmem_class = class_create(THIS_MODULE, "globalmem_cls");
create_dev_node(0);

globalmem_devp = kmalloc(2 * sizeof(struct globalmem_dev), GFP_KERNEL);
if (! globalmem_devp){
result = -ENOMEM;
goto fail_malloc;
}
memset(globalmem_devp, 0, 2 * sizeof(struct globalmem_dev));
globalmem_setup_cdev(&globalmem_devp[0], 0);
globalmem_setup_cdev(&globalmem_devp[1], 1);

return 0;

fail_malloc:
unregister_chrdev_region(devno, 1);
return result;
}

static void __exit globalmem_exit(void){
cdev_del(&globalmem_devp[0].cdev);

cdev_del(&globalmem_devp[1].cdev);
kfree(globalmem_devp);
unregister_chrdev_region(MKDEV(globalmem_major, 0), 2);
class_destroy(globalmem_class);
}

module_param(globalmem_major, int, S_IRUGO);

//honeywell 臧春杰
module_init(globalmem_init);
module_exit(globalmem_exit);

这个代码我在ubuntu16.04上编译测试过。

结果如下

ubuntu@ubuntu-VirtualBox:~/driver/test3$ ls -l /dev/ | grep global
crw------- 1 root root 247, 0 8月 25 13:14 globalmem_cj1
crw------- 1 root root 247, 1 8月 25 13:14 globalmem_cj2

可以直接拷贝，写个makefile编译，后续我再加点自动创建设备节点。就不用自己mknod了。