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标题:
OMAPL138的内存映射是否在Linux下已经完成？？？
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作者:
zc_fly
时间:
2014-8-19 16:38
标题:
OMAPL138的内存映射是否在Linux下已经完成？？？
本帖最后由 zc_fly 于 2014-8-19 16:53 编辑
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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>
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#include <unistd.h>
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#include <sys/mman.h>
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#include <sys/types.h>
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#include <fcntl.h>
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#define SHAER_RAM_BASE_ADDR (0x80000000)
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typedef struct
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{
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unsigned int a;
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unsigned int b;
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unsigned int packet_cout;
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}RX_MSG_PROTOCOL, *pRX_MSG_PROTOCOL;
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void read_MSG_buffer(pRX_MSG_PROTOCOL pshreRAM);
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unsigned int count_copy = 0;
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int main()
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{
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pRX_MSG_PROTOCOL pshreRAM = NULL;
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pshreRAM = (pRX_MSG_PROTOCOL)SHAER_RAM_BASE_ADDR;
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while(1)
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{
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read_MSG_buffer(pshreRAM);
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}
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}
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void read_MSG_buffer(pRX_MSG_PROTOCOL pshreRAM)
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{
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RX_MSG_PROTOCOL buf;
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buf.a = pshreRAM->a;
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buf.b = pshreRAM->b;
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buf.packet_cout = pshreRAM->packet_cout;
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if(buf.packet_cout != count_copy)
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{
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printf("a is %d\n", buf.a);
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printf("b is %d\n", buf.b);
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printf("count is %d\n", buf.packet_cout);
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count_copy = buf.packet_cout;
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}
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else
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{
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printf("No effective message!");
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}
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}
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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。
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使用下面代码，对内存使用了mmap函数后：
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/mman.h>
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#include <sys/types.h>
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#include <fcntl.h>
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#define SHAER_RAM_BASE_ADDR (0x80000000)
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#define SHAER_RAM_SIZE (0x20000)
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typedef struct
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{
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unsigned int a;
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unsigned int b;
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unsigned int packet_cout;
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}RX_MSG_PROTOCOL, *pRX_MSG_PROTOCOL;
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void read_MSG_buffer(int *baseaddr);
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unsigned int count_copy = 0;
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int main()
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{
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int fd;
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int *mem = NULL;
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if((fd = open("/dev/mem", O_RDWR)) <0)
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{
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perror("open error");
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return -1;
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}
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mem = mmap((void *)SHAER_RAM_BASE_ADDR, SHAER_RAM_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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while(1)
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{
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read_MSG_buffer(mem);
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}
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}
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void read_MSG_buffer(int *baseaddr)
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{
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pRX_MSG_PROTOCOL pshreRAM = NULL;
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pshreRAM = (pRX_MSG_PROTOCOL)baseaddr;
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if(pshreRAM->packet_cout != count_copy)
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{
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printf("a is %d\n", pshreRAM->a);
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printf("b is %d\n", pshreRAM->b);
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printf("count is %d\n", pshreRAM->packet_cout);
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count_copy = pshreRAM->packet_cout;
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}
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else
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{
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printf("No effective message!\n");
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}
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}
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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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