LINUX下读写寄存器.doc

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 plaincopy #include #include #include #include /* printk() */ #include /* kmalloc() */ #include /* everything. */ #include /* error codes */ #include /* size_t */ #include #include /* O_ACCMODE */ #include #include #include #include #include /* cli(), *_flags */ #include /* copy_*_user */ #include #define LED_NUM 4 struct led_dev struct cdev dev; unsigned port; unsigned long offset; ; struct led_dev led4; dev_t dev = 0; static struct resource *led_resource; int led_open(struct inode *inode, struct file *filp) struct led_dev *led; /* device information */ led = container_of(inode-i_cdev, struct led_dev, dev); filp-private_data = led; /* for other methods */ return 0; /* success */ 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 writen); led = (struct led_dev *)filp-private_data; copy_from_user(&data,buf,count); if(data = 0) printk(KERN_INFO debug by baikal: led offn); value = inl(unsigned)(S3C2410_GPBDAT); outl(value | 1offset,(unsigned)(S3C2410_GPBDAT); /value = ioread32(led-base); /iowrite32( value | 1offset, led-base); else printk(KERN_INFO debug by baikal: led onn); value = inl(unsigned)(S3C2410_GPBDAT); outl(value & (1offset),(unsigned)(S3C2410_GPBDAT); /value = ioread32(led-base); /iowrite32( value & (1offset), 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: cant get major %dn, MAJOR(dev); return result; led_resource = request_region(0x56000014,0x4,led); if(led_resource = NULL) printk(KERN_ERR Unable to register LED I/O addressesn); return -1; for(i = 0; i LED_NUM; i+) cdev_init( &ledi.dev, &led_fops); /ledi.port = ioport_map(0x56000014,0x4); /ledi.base = ioremap(0x56000014,0x4); ledi.offset = i + 5; /leds GPB5678 ledi.dev.owner = THIS_MODULE; ledi.dev.ops = &led_fops; result = cdev_add(&ledi.dev,MKDEV(MAJOR(dev),i),1); if(result 0) printk(KERN_ERR LED: cant add led%dn,i); return result; return 0; static void led_exit(void) int i; release_region(0x56000014,0x4); for( i = 0; i LED_NUM; i+) /iounmap(ledi.base); cdev_del(&ledi.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 plaincopy #include #include #include #include /* printk() */ #include /* kmalloc() */ #include /* everything. */ #include /* error codes */ #include /* size_t */ #include #include /* O_ACCMODE */ #include #include #include #include /* cli(), *_flags */ #include /* copy_*_user */ #include #define LED_NUM 4 struct led_dev struct cdev dev; void _iomem *base; unsigned long offset; ; struct led_dev led4; dev_t dev = 0; int led_open(struct inode *inode, struct file *filp) struct led_dev *led; /* device information */ led = container_of(inode-i_cdev, struct led_dev, dev); filp-private_data = led; /* for other methods */ return 0; /* success */ 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 writen); led = (struct led_dev *)filp-private_data; copy_from_user(&data,buf,count); if(data = 0) printk(KERN_INFO debug by baikal: led offn); value = ioread32(led-base); iowrite32( value | 1offset, led-base); else printk(KERN_INFO debug by baikal: led onn); value = ioread32(led-base); iowrite32( value & (1offset), 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: cant get major %dn, MAJOR(dev); return result; for(i = 0; i LED_NUM; i+) cdev_init( &ledi.dev, &led_fops); request_mem_region(0x56000014,0x4,led); ledi.base = ioremap(0x56000014,0x4); ledi.offset = i + 5; /leds GPB5678 ledi.dev.owner = THIS_MODULE; ledi.dev.ops = &led_fops; result = cdev_add(&ledi.dev,MKDEV(MAJOR(dev),i),1); if(result 0) printk(KERN_ERR LED: cant add led%dn,i); return result; return 0; static void led_exit(void) int i; release_mem_region(0x56000014,0x4); for( i = 0; i LED_NUM; i+) iounm