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  • Linux下读写寄存器

    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:

    #include <linux/module.h>
    #include <linux/moduleparam.h>
    #include <linux/init.h>

    #include <linux/kernel.h> /* printk() */
    #include <linux/slab.h>  /* kmalloc() */
    #include <linux/fs.h>  /* everything... */
    #include <linux/errno.h> /* error codes */
    #include <linux/types.h> /* size_t */
    #include <linux/proc_fs.h>
    #include <linux/fcntl.h> /* O_ACCMODE */
    #include <linux/seq_file.h>
    #include <linux/cdev.h>
    #include <linux/ioport.h>

    #include <mach/regs-gpio.h>
    #include <asm/system.h>  /* cli(), *_flags */
    #include <asm/uaccess.h> /* copy_*_user */
    #include <asm/io.h>

    #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; /* 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 write ");
     
     led = (struct led_dev *)filp->private_data;
     copy_from_user(&data,buf,count);
     if(data == '0')
     { 
      printk(KERN_INFO "debug by baikal: led off "); 
      value = inl((unsigned)(S3C2410_GPBDAT));
      outl(value | 1<<led->offset,(unsigned)(S3C2410_GPBDAT)); 
      //value = ioread32(led->base);
      //iowrite32( value | 1<<led->offset, led->base);  
     }
     else
     {
      printk(KERN_INFO "debug by baikal: led on ");
      value = inl((unsigned)(S3C2410_GPBDAT));
      outl(value & ~(1<<led->offset),(unsigned)(S3C2410_GPBDAT)); 
      //value = ioread32(led->base);
      //iowrite32( value & ~(1<<led->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 ", 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 ");
      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  GPB5678
      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 ",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:

    #include <linux/module.h>
    #include <linux/moduleparam.h>
    #include <linux/init.h>

    #include <linux/kernel.h> /* printk() */
    #include <linux/slab.h>  /* kmalloc() */
    #include <linux/fs.h>  /* everything... */
    #include <linux/errno.h> /* error codes */
    #include <linux/types.h> /* size_t */
    #include <linux/proc_fs.h>
    #include <linux/fcntl.h> /* O_ACCMODE */
    #include <linux/seq_file.h>
    #include <linux/cdev.h>
    #include <linux/ioport.h>

    #include <asm/system.h>  /* cli(), *_flags */
    #include <asm/uaccess.h> /* copy_*_user */
    #include <asm/io.h>

    #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; /* 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 write ");
     
     led = (struct led_dev *)filp->private_data;
     copy_from_user(&data,buf,count);
     if(data == '0')
     { 
      printk(KERN_INFO "debug by baikal: led off ");  
      value = ioread32(led->base);
      iowrite32( value | 1<<led->offset, led->base);  
     }
     else
     {
      printk(KERN_INFO "debug by baikal: led on ");
      value = ioread32(led->base);
      iowrite32( value & ~(1<<led->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 ", 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  GPB5678
      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 ",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");

    目前,对于具体体系上的linux在移植过程中如何实现这两种方式的方法还不清楚,现在只是会用。等以后有机会了再慢慢理清楚。

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  • 原文地址:https://www.cnblogs.com/lidabo/p/6402202.html
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