转自：http://blog.csdn.net/xyyangkun/article/details/7830149
版权声明：本文为博主原创文章，未经博主允许不得转载。
这是在mini6410上测试成功的，在没有驱动的情况下用程序直接控制了led灯test_mmap.c：
- /* Example how to access the value of the on-board DIP switches on
- * HiCO.SH7760. You can compile the program with command:
- *
- * sh4-linux-gcc -Wall dip_switch.c -o dip_switch
- */
- #include <stdio.h>
- #include <stdlib.h>
- #include <assert.h>
- #include <unistd.h>
- #include <errno.h>
- #include <fcntl.h>
- #include <sys/mman.h>
- #define MAP_SIZE 4096UL
- #define MAP_MASK (MAP_SIZE - 1)
- int main(void) {
- int fd;
- void *map_base, *virt_addr;
- /* Physical address of the DIP switch GPIO register on HiCO.SH7760 (See
- * the HiCO.SH7760 hardware manual
- *
- * _NOTE_: the dipswitches also define how the system boots (i.e. the value
- * is used by the bootloader at startup), so oafter testting, leave the
- * switches in the same position as they were */
- off_t target = 0x7F008800; //GPKCON0 0x7F008800
- if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1) {
- printf("/dev/mem could not be opened.\n");
- perror("open");
- exit(1);
- } else {
- printf("/dev/mem opened.\n");
- }
- /* Map one page */
- map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~MAP_MASK);
- if(map_base == (void *) -1) {
- printf("Memory map failed.\n");
- perror("mmap");
- } else {
- printf("Memory mapped at address %p.\n", map_base);
- }
- virt_addr = map_base + (target & MAP_MASK);
- /* acess remapped region here */
- printf("Now try to change the value of the on-board DIP switche\n");
- *(unsigned int *)virt_addr=0x11110000;//0x1111<<16;//设定为输出状态
- int ab=*(unsigned int *)virt_addr;
- //*(unsigned int *)(virt_addr+8)=0xffffffff;
- printf("ab=%x\n",ab);
- #if 1
- while(1){
- *(volatile unsigned int *)(virt_addr+8)=0x00; //一定要是virt_addr不能是map_base//置０亮
- printf("1value is 0x%x\n",*(unsigned int *)(virt_addr+8));
- printf("2value is 0x%x\n",*(unsigned int *)virt_addr);
- sleep(1); //一定要有要不很快，人眼发现不了
- *(volatile unsigned int *)(virt_addr+8)=0xf0; //置１灭
- printf("3value is 0x%x\n",*(unsigned int *)(virt_addr+8));
- printf("4value is 0x%x\n",*(unsigned int *)virt_addr);
- sleep(1); //一定要有要不很快，人眼发现不了
- }
- #endif
- /* we'll never get here in this example, but here's how the region is
- * unmapped. */
- if(munmap(map_base, MAP_SIZE) == -1) {
- printf("Memory unmap failed.\n");
- }
- close(fd);
- }
以上程序证明了在linux下用mmap函数可以在没有驱动的情况下也可以直接控制底层。
网上说只能控制gpio设备，我还可以直接控制其它设备，有待验证。