OMAPL138的内存映射是否在Linux下已经完成？？？

zc_fly · 发表于 2014-8-19 16:38:00

本帖最后由 zc_fly 于 2014-8-19 16:53 编辑

OMAPL138的ARM端对共享区内存进行直接访问，代码如下所示：#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <fcntl.h>

#define SHAER_RAM_BASE_ADDR (0x80000000)

typedef struct
{
      unsigned int a;
      unsigned int b;
      unsigned int packet_cout;
}RX_MSG_PROTOCOL, *pRX_MSG_PROTOCOL;

void read_MSG_buffer(pRX_MSG_PROTOCOL pshreRAM);
unsigned int count_copy = 0;

int main()
{
      pRX_MSG_PROTOCOL pshreRAM = NULL;
      pshreRAM = (pRX_MSG_PROTOCOL)SHAER_RAM_BASE_ADDR;

      while(1)
      {
            read_MSG_buffer(pshreRAM);
      }
}

void read_MSG_buffer(pRX_MSG_PROTOCOL pshreRAM)
{
      RX_MSG_PROTOCOL buf;

      buf.a = pshreRAM->a;
      buf.b = pshreRAM->b;
      buf.packet_cout = pshreRAM->packet_cout;

      if(buf.packet_cout != count_copy)
      {
            printf("a is %d\n", buf.a);
            printf("b is %d\n", buf.b);
            printf("count is %d\n", buf.packet_cout);
            count_copy = buf.packet_cout;
      }
      else
      {
            printf("No effective message!");
      }
}

但是出现segmentation fault的问题，这是什么原因啊？？？我在DSP端烧写了一段小程序，向共享区0x80000000位置写入数据，用CCS 测试发现写入成功。
使用下面代码，对内存使用了mmap函数后：
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <fcntl.h>

#define SHAER_RAM_BASE_ADDR (0x80000000)
#define SHAER_RAM_SIZE       (0x20000)

typedef struct
{
      unsigned int a;
      unsigned int b;
      unsigned int packet_cout;
}RX_MSG_PROTOCOL, *pRX_MSG_PROTOCOL;

void read_MSG_buffer(int *baseaddr);
unsigned int count_copy = 0;

int main()
{
      int fd;
      int *mem = NULL;

      if((fd = open("/dev/mem", O_RDWR)) <0)
      {
            perror("open error");
            return -1;
      }

      mem = mmap((void *)SHAER_RAM_BASE_ADDR, SHAER_RAM_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

      while(1)
      {
            read_MSG_buffer(mem);
      }
}

void read_MSG_buffer(int *baseaddr)
{
      pRX_MSG_PROTOCOL pshreRAM = NULL;

      pshreRAM = (pRX_MSG_PROTOCOL)baseaddr;

      if(pshreRAM->packet_cout != count_copy)
      {
            printf("a is %d\n", pshreRAM->a);
            printf("b is %d\n", pshreRAM->b);
            printf("count is %d\n", pshreRAM->packet_cout);
            count_copy = pshreRAM->packet_cout;
      }
      else
      {
            printf("No effective message!\n");
      }
}

没有出现segmentation fault这个错误，但是读出来的数据均为0。这该怎样解决啊？？？主要问题还是在Linux系统下，OMAPL138是否可以直接访问映射地址？？？该怎样实现？？？

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