linux kernel 怎么读cpu写寄存器 inw

linux kernel 怎么读cpu写寄存器 inw

arm裸机下读写寄存器很容易,各个寄存器和内存的地址是单一地址空间,他们是用相同的指令进行读写操作的.而在linux下就要复杂很多,因为linux支持多个体系架构的CPU。比如arm和x86就不一样，具体的差别我暂时也说不上来，这个涉及到CPU体系的设计。目前我只关心：linux为了支持多个硬件体系，在IO访问上做了自己的接口。可以通过IO内存和IO端口这两种方式进行IO访问。在LED的例子上给出这两种方式的具体实现：
1.利用IO Port的方式：

[cpp] view plain copy
#include
#include
#include

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

#include
#include
#include
#include

#define LED_NUM 4

struct led_dev
{
struct cdev dev;
unsigned port;
unsigned long offset;
};

struct led_dev led[4];
dev_t dev = 0;
static struct resource *led_resource;

int led_open(struct inode *inode, struct file *filp)
{
struct led_dev *led;

led = container_of(inode->i_cdev, struct led_dev, dev);
filp->private_data = led;

return 0;
}

int led_release(struct inode *inode, struct file *filp)
{
return 0;
}

ssize_t led_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
return 0;
}

ssize_t led_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
{
char data;
struct led_dev *led;
u32 value;
printk(KERN_INFO "debug by baikal: led dev write\n");

led = (struct led_dev *)filp->private_data;
copy_from_user(&data,buf,count);
if(data == '0')
{
printk(KERN_INFO "debug by baikal: led off\n");
value = inl((unsigned)(S3C2410_GPBDAT));
outl(value | 1<offset,(unsigned)(S3C2410_GPBDAT));
//value = ioread32(led->base);
//iowrite32( value | 1<offset, led->base);
}
else
{
printk(KERN_INFO "debug by baikal: led on\n");
value = inl((unsigned)(S3C2410_GPBDAT));
outl(value & ~(1<offset),(unsigned)(S3C2410_GPBDAT));
//value = ioread32(led->base);
//iowrite32( value & ~(1<offset), led->base);
}
}

struct file_operations led_fops = {
.owner = THIS_MODULE,
.read = led_read,
.write = led_write,
//.ioctl = led_ioctl,
.open = led_open,
.release = led_release,
};

static int led_init(void)
{
int result, i;

result = alloc_chrdev_region(&dev, 0, LED_NUM,"LED");
if (result < 0) {
printk(KERN_WARNING "LED: can't get major %d\n", MAJOR(dev));
return result;
}
led_resource = request_region(0x56000014,0x4,"led");
if(led_resource == NULL)
{
printk(KERN_ERR " Unable to register LED I/O addresses\n");
return -1;
}
for(i = 0; i < LED_NUM; i++)
{
cdev_init( &led[i].dev, &led_fops);
//led[i].port = ioport_map(0x56000014,0x4);
//led[i].base = ioremap(0x56000014,0x4);
led[i].offset = i + 5; //leds GPB5\6\7\8
led[i].dev.owner = THIS_MODULE;
led[i].dev.ops = &led_fops;
result = cdev_add(&led[i].dev,MKDEV(MAJOR(dev),i),1);
if(result < 0)
{
printk(KERN_ERR "LED: can't add led%d\n",i);
return result;
}
}

return 0;
}

static void led_exit(void)
{
int i;
release_region(0x56000014,0x4);
for( i = 0; i < LED_NUM; i++)
{
//iounmap(led[i].base);

cdev_del(&led[i].dev);
}
unregister_chrdev_region(dev, LED_NUM);

}

module_init(led_init);
module_exit(led_exit);

MODULE_AUTHOR("Baikal");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Simple LED Driver");

2.利用IO Mem的方式：

[cpp] view plain copy
#include
#include
#include

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

#include
#include
#include

#define LED_NUM 4

struct led_dev
{
struct cdev dev;
void __iomem *base;
unsigned long offset;
};

struct led_dev led[4];
dev_t dev = 0;

int led_open(struct inode *inode, struct file *filp)
{
struct led_dev *led;

led = container_of(inode->i_cdev, struct led_dev, dev);
filp->private_data = led;

return 0;
}

int led_release(struct inode *inode, struct file *filp)
{
return 0;
}

ssize_t led_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
return 0;
}

ssize_t led_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
{
char data;
struct led_dev *led;
u32 value;
printk(KERN_INFO "debug by baikal: led dev write\n");

led = (struct led_dev *)filp->private_data;
copy_from_user(&data,buf,count);
if(data == '0')
{
printk(KERN_INFO "debug by baikal: led off\n");
value = ioread32(led->base);
iowrite32( value | 1<offset, led->base);
}
else
{
printk(KERN_INFO "debug by baikal: led on\n");
value = ioread32(led->base);
iowrite32( value & ~(1<offset), led->base);
}
}

struct file_operations led_fops = {
.owner = THIS_MODULE,
.read = led_read,
.write = led_write,
//.ioctl = led_ioctl,
.open = led_open,
.release = led_release,
};

static int led_init(void)
{
int result, i;

result = alloc_chrdev_region(&dev, 0, LED_NUM,"LED");
if (result < 0) {
printk(KERN_WARNING "LED: can't get major %d\n", MAJOR(dev));
return result;
}

for(i = 0; i < LED_NUM; i++)
{
cdev_init( &led[i].dev, &led_fops);
request_mem_region(0x56000014,0x4,"led");
led[i].base = ioremap(0x56000014,0x4);
led[i].offset = i + 5; //leds GPB5\6\7\8
led[i].dev.owner = THIS_MODULE;
led[i].dev.ops = &led_fops;
result = cdev_add(&led[i].dev,MKDEV(MAJOR(dev),i),1);
if(result < 0)
{
printk(KERN_ERR "LED: can't add led%d\n",i);
return result;
}
}

return 0;
}

static void led_exit(void)
{
int i;
release_mem_region(0x56000014,0x4);
for( i = 0; i < LED_NUM; i++)
{
iounmap(led[i].base);

cdev_del(&led[i].dev);
}
unregister_chrdev_region(dev, LED_NUM);

}

module_init(led_init);
module_exit(led_exit);

MODULE_AUTHOR("Baikal");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Simple LED Driver");

linux内核的c语言源文件。 至于用途，对于一般用户来说主要就是自己来定制和编译内核文件了，用来定制自己的linux系统。学习者还可以通过它来学习操作系统的开发。高手可以修改这些源文件，进一步改进系统。 搞明白一个操作系统可不是件简单的事情，看懂源码就更不容易了 最原始的 0.11版的linux内核都要好几万行代码 用gcc编译一下kernel文件,就成了内核镜像了 开机时要把镜像加载进内存 在加上gnu和一些软件,就是一个比较完整的linux 要弄明白内核结构,多研究研究makefile文件

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