如何在udev自动创建设备节点

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/fs.h>

#include <linux/init.h>

#include <linux/delay.h>

#include <linux/irq.h>

#include <asm/uaccess.h>

#include <asm/irq.h>

#include <asm/io.h>

#include <asm/arch/regs-gpio.h>

#include <asm/hardware.h>

#include <linux/poll.h>

#include <linux/dma-mapping.h>

#include "xdmaps_hw.h"

#define MEM_CPY_NO_DMA  0

#define MEM_CPY_DMA     1

#define BUF_SIZE  (512*1024)

#define XPS_DMA0_ABORT_INT_ID 45

#define XPS_DMA0_INT_ID 46

#define XPS_DMA1_INT_ID 47

#define XPS_DMA2_INT_ID 48

#define XPS_DMA3_INT_ID 49

#define XPS_DMA4_INT_ID 72

#define XPS_DMA5_INT_ID 73

#define XPS_DMA6_INT_ID 74

#define XPS_DMA7_INT_ID 75

#define DMA0_BASE_ADDR  0xf8003000

struct s3c_dma_regs {

unsigned long disrc;

unsigned long disrcc;

unsigned long didst;

unsigned long didstc;

unsigned long dcon;

unsigned long dstat;

unsigned long dcsrc;

unsigned long dcdst;

unsigned long dmasktrig;

};

unsigned int chanid;

static int major = 0;

static char *src;

static dma_addr_t *src_phys;

static char *dst;

static dma_addr_t *dst_phys;

static struct class *cls;

static volatile struct s3c_dma_regs *dma_regs;

static DECLARE_WAIT_QUEUE_HEAD(dma_waitq);

/* 中断事件标志, 中断服务程序将它置1，ioctl将它清0 */

static volatile int ev_dma = 0;

static int s3c_dma_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

{
int i;
chanid = arg;

memset(src, 0xAA, BUF_SIZE);

memset(dst, 0x55, BUF_SIZE);

switch (cmd)

{

                //这是非DMA模式

case MEM_CPY_NO_DMA :

{

for (i = 0; i < BUF_SIZE; i++)

dst[i] = src[i];  //CPU直接将源拷贝到目的

if (memcmp(src, dst, BUF_SIZE) == 0)//这个函数见注释2

{

printk("MEM_CPY_NO_DMA OK\n");

}

else

{

printk("MEM_CPY_DMA ERROR\n");

}

break;

}

                //这是DMA模式
case MEM_CPY_DMA :{
ev_dma = 0;

/* 把源,目的,长度告诉DMA */

                        /* 关于下面寄存器的具体情况，我们在注释3

里面来详细讲一下 */
dma_regs->disrc      = src_phys;        /* 源的物理地址 */
dma_regs->disrcc     = (0<<1) | (0<<0); /* 源位于AHB总线, 源地址递增 */
dma_regs->didst      = dst_phys;        /* 目的的物理地址 */
dma_regs->didstc     = (0<<2) | (0<<1) | (0<<0); /* 目的位于AHB总线, 

目的地址递增 */
dma_regs->dcon       = (1<<30)|(1<<29)|(0<<28)|(1<<27)|(0<<23)|(0<<20)|(
BUF_SIZE<<0);  /* 使能中断,单个传输,软件触发, */

/* 启动DMA */
dma_regs->dmasktrig  = (1<<1) | (1<<0);

/* 如何知道DMA什么时候完成? */

/* 休眠 */
wait_event_interruptible(dma_waitq, ev_dma);

if (memcmp(src, dst, BUF_SIZE) == 0){
printk("MEM_CPY_DMA OK\n");
}else{
printk("MEM_CPY_DMA ERROR\n");
}
break;
}

}

return 0;

}

s3c_dma_open(struct inode *inode, struct file *file)

{

return 0;

}

static struct file_operations dma_fops = {
.owner  = THIS_MODULE,
.unlocked_ioctl  = s3c_dma_ioctl,
.open  = s3c_dma_open,

};

static irqreturn_t s3c_dma_irq(int irq, void *devid)

{
unsigned int value;

printk("DMA get irq status\n");
value = read32(dma_regs+XDMAPS_INTSTATUS_OFFSET);
printk("Interrupt status before clearing %x\r\n", value);
write32(dma_regs+XDMAPS_INTCLR_OFFSET, 1<<chanid);
value = read32(dma_regs+XDMAPS_INTSTATUS_OFFSET);
printk("Interrupt status after clearing %x\r\n", value);

/* 唤醒 */
ev_dma = 1;
wake_up_interruptible(&dma_waitq);   /* 唤醒休眠的进程 */

return IRQ_HANDLED;

}

static irqreturn_t s3c_abort_irq(int irq, void *devid)

{
printk("DMA get abort status\n");
return IRQ_HANDLED;

}

static int s3c_dma_init(void)

{

         /* 这里注册一个中断，当DMA数据传输完毕之后会发生此中断 */
if (request_irq(XPS_DMA0_INT_ID, s3c_dma_irq, 0, "s3c_dma", 1)){
printk("can't request_irq INT for DMA\n");
return -EBUSY;
}
if (request_irq(XPS_DMA0_ABORT_INT_ID, s3c_abort_irq, 0, "s3c_dma", 1)){
free_irq(XPS_DMA0_INT_ID, 1);
printk("can't request_irq ABORT for DMA\n");
return -EBUSY;
}

/* 分配SRC, DST对应的缓冲区，关于此函数详见注释1 */

src = dma_alloc_writecombine(NULL, BUF_SIZE, &src_phys, GFP_KERNEL);//源

if (NULL == src)

{

printk("can't alloc buffer for src\n");

free_irq(XPS_DMA0_INT_ID, 1);

free_irq(XPS_DMA0_ABORT_INT_ID, 1);

return -ENOMEM;

}

dst = dma_alloc_writecombine(NULL, BUF_SIZE, &dst_phys, GFP_KERNEL);//目的

if (NULL == dst)

{

free_irq(XPS_DMA0_INT_ID, 1);

free_irq(XPS_DMA0_ABORT_INT_ID, 1);

dma_free_writecombine(NULL, BUF_SIZE, src, src_phys);

printk("can't alloc buffer for dst\n");

return -ENOMEM;

}

major = register_chrdev(0, "s3c_dma", &dma_fops);//注册字符设备

/* 为了自动创建设备节点 */

cls = class_create(THIS_MODULE, "s3c_dma");

device_create(cls, NULL, MKDEV(major, 0), NULL, "dma"); /* /dev/dma */

dma_regs = ioremap(DMA0_BASE_ADDR, 0x1000);//这边是将DMA控制寄存器映射到内核空间
return 0;

}

static void s3c_dma_exit(void)

{

iounmap(dma_regs);

device_destroy(cls, MKDEV(major, 0));

class_destroy(cls);

unregister_chrdev(major, "s3c_dma");

dma_free_writecombine(NULL, BUF_SIZE, src, src_phys);

dma_free_writecombine(NULL, BUF_SIZE, dst, dst_phys);

free_irq(XPS_D
4000
MA0_INT_ID, 1);

free_irq(XPS_DMA0_ABORT_INT_ID, 1);

}

module_init(s3c_dma_init);

module_exit(s3c_dma_exit);

MODULE_LICENSE("GPL");