led.c arm入门练习 交叉编译

gistfile1.c

#include "led.h"

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>	/* Param header */

#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/types.h>

#include <asm/uaccess.h>	/* 资源控制 */
#include <linux/sched.h>	/* 进程控制 */
#include <asm/io.h>		/* 内存读写方法
				 * read: ioread32
				 * write: iowrite32*/


#define DRIVER_AUTHOR "icecream <[email protected]>"
#define DRIVER_DESC "A sample driver"

/* 引入两个变量 */
module_param(mymajor, int, 0644);
module_param(name, charp, 0644);

/* 自己封装，以自己需求 */
struct led_dev {
  struct cdev cdev;
  unsigned int* caddr;		/* 代表ARM中的控制寄存器 0x56000010 */
  unsigned int* daddr;		/* 代表ARM中的数据寄存器 0x56000014 */
};
struct led_dev* led_dev;	/* 全局指针，方便后面的引用 */


/*　读写操作 */
/* inode描述节点，file描述的是系统中的 */
static int led_open(struct inode* inode, struct file* file) 
{
  struct led_dev* led_dev;
  /* 根据结构体中的一个成员来获取到整个结构体的内容: struct led_dev, cdev */
  /* inode 代表一个设备, 后面获取的结构体会放到其中*/
  led_dev = container_of(inode->i_cdev, struct led_dev, cdev);
  /* 保存led灯的私有数据，让灯与灯之间数据私有 */
  file->private_data = led_dev;
  /* ACCMODE当前文件权限 */
  if ((file->f_flags & O_ACCMODE) == O_WRONLY) {
    file->f_pos = 0;		/* 保证每次写数据从起始写到最后 */
    printk ("open suc[w]\n");
  }
  return 0;
}

static int led_close(struct inode* inode, struct file* file)
{
  /* 系统会帮忙清理，这里只是简单的打印提示 */
  printk ("led_close Close\n");
  return 0;
}


/* 控制灯 */
static void setup(unsigned long num, int p)
{
  unsigned int v = *(led_dev->daddr); /* 获取内容 */
  if (p) {			      
    /* 灯亮 */
    /* 为何+4, 难道是移动到下一个位？0x56000010 */
    unsigned int t = ~(0x01 << (num + 4));
    v &= t;			/* clear 0 */
  } else {			
    /* 灯灭 */
    unsigned int t = (0x01 << (num+4));
    v |= t;			/* set 1 */
  }

  /* 写回数据寄存器 */
  iowrite32(v, led_dev->daddr);
}

/*  */
//arg: 第几个灯
//cmd: LED_ON(1), LED_OFF(0)
static int led_ioctl(struct inode* inode, struct file* file
		    , unsigned int cmd, unsigned long arg)
{
  switch(cmd) {
  case LED_ON:
    setup(arg, 1);
    break;
  default:
    setup(arg, 0);
    break;
  }
  return 0;
}

static const struct file_operations fops = {
  .open = led_open,
  .release = led_close,
  .ioctl = led_ioctl,
  /* .compat_ioctl = led_ioctl, */
  .owner = THIS_MODULE
};

static int __init led_init(void) 
{
    int ret;
    dev_t devno;
    unsigned int out = 0;

    devno = MKDEV(mymajor, 0);
    ret = register_chrdev_region(devno, 1, name);
    if (ret < 0) {
      alloc_chrdev_region(&devno, 0, 1, name);
      mymajor = MAJOR(devno);
    }
    printk ("Major: %d, Minor: %d\n", mymajor, MINOR(devno));

    /* request memory */
    led_dev = (unsigned int*)kmalloc(sizeof(led_dev), GFP_KERNEL);
    if (led_dev) {
      printk ("Get memory successfully!\n");
    } else {
      printk ("Get memory error!\n");
      return ENOMEN;
    }

    /* 对硬件到初始化 */
    /* 从内存空间映射的上层虚拟空间, 4:映射长度 */
    led_dev->caddr = (unsigned int*)ioremap(0x56000010, 4);
    led_dev->daddr = (unsigned int*)ioremap(0x56000014, 4);

    out = *(led_dev->caddr);
    /* GPB5/6/7/8 --> 10,11;12,13;14,15;16,17 */
    /*                01 01 01 01 */
    /* 01 输出 */
    out |= 0x01 << 10;
    out |= 0x01 << 12;
    out |= 0x01 << 14;
    out |= 0x01 << 16;
    iowrite32(out, led_dev->caddr);
    /* iowrite8(): 每次写入8字节 */
    /* iowrite16() 半字*/
    /* iowrite32() 1个字*/

    /* init cdev structor */
    cdev_init(&led_dev->cdev, &fops);
    led_dev->cdev.owner = THIS_MODULE;
    led_dev->cdev.ops = &fops;
    if ((cdev_add(&led_dev->cdev, devno, 1))) {
      printk ("add successfully!\n");
    } else {
      printk ("add error!\n");
    }
  
    return 0;
  }

static void __exit led_exit(void)
{
  dev_t devno = MKDEV(mymajor, 0);

  cdev_del(&led_dev->cdev);
  /* 解除两个映射 */
  iounmap(&led_dev->caddr);
  iounmap(&led_dev->daddr);
  /* 释放空间 */
  kfree(led_dev);
  led_dev = NULL;
  /* 卸载设备 */
  unregister_chrdev_region(devno, 1);

  printk("Exit the driver module!\n");
}

module_init(led_init); 	/* enter */
module_exit(led_exit);	/* out */

MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_ALIAS("Linux Module");