Mmap Direct control of the bottom "turn"

Transferred from: http://blog.csdn.net/xyyangkun/article/details/7830149

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

This is a successful test on the mini6410, with no driver in the case of direct control of the LED lamp test_mmap.c:

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2. /* Example How to access the value of the on-board DIP switches on
4. * hico.sh7760. Can compile the program with command:
6. *
8. * Sh4-linux-gcc-wall Dip_switch.c-o Dip_switch
10. */
12. #include <stdio.h>
14. #include <stdlib.h>
16. #include <assert.h>
18. #include <unistd.h>
20. #include <errno.h>
22. #include <fcntl.h>
24. #include <sys/mman.h>
28. #define Map_size 4096UL
30. #define MAP_MASK (MAP_SIZE-1)
36. int main (void) {
38. int fd;
40. void *map_base, *virt_addr;
44. /* Physical Address of the DIP switch GPIO Register on hico.sh7760 ( see
46. * The hico.sh7760 Hardware manual
48. *
50. * _note_: The dipswitches also define how the system boots (i.e. the value
52. * is used by the bootloader in startup), so Oafter testting, leave the
54. * Switches in the same position as they were * *
56. off_t target = 0x7f008800; //gpkcon0 0x7f008800
60. if (fd = open ("/dev/mem", O_RDWR | O_sync)) = =-1) {
62. printf ("/dev/mem could not being opened.\n");
64. Perror ("open");
66. Exit (1);
68. } Else {
70. printf ("/dev/mem opened.\n");
72. }
76. / * MAP one page * /
78. Map_base = mmap (0, map_size, Prot_read | Prot_write, map_shared, FD, Target & ~map_mask);
80. if (map_base = = (void *)-1) {
82. printf ("Memory map failed.\n");
84. Perror ("mmap");
86. } Else {
88. printf ("Memory mapped at address%p.\n", map_base);
90. }
94. VIRT_ADDR = Map_base + (target & Map_mask);
98. / * acess remapped Region here */
102. printf ("Now try to change the value of the on-board DIP switche\n");
104. * (unsigned int *) virt_addr=0x11110000; //0x1111<<16;//set to output state
106. int ab=* (unsigned int *) virt_addr;
108. //* (unsigned int *) (virt_addr+8) =0xffffffff;
110. printf ("ab=%x\n", AB);
114. #if 1
116. While (1) {
118. * (volatile unsigned int *) (virt_addr+8) =0x00; //Must be if virt_addr cannot be map_base//0 bright
120. printf ("1value is 0x%x\n", * (unsigned int *) (virt_addr+8));
122. printf ("2value is 0x%x\n", * (unsigned int *) VIRT_ADDR);
124. Sleep (1); //must have or not soon, the human eye can not find
126. * (volatile unsigned int *) (virt_addr+8) =0xf0; //Reset 1 off
128. printf ("3value is 0x%x\n", * (unsigned int *) (virt_addr+8));
130. printf ("4value is 0x%x\n", * (unsigned int *) VIRT_ADDR);
132. Sleep (1); //must have or not soon, the human eye can not find
134. }
136. #endif
138. /* We' ll never get here on this example
140. * unmapped. */
142. if (Munmap (map_base, map_size) = =-1) {
144. printf ("Memory unmap failed.\n");
146. }
150. Close (FD);
152. }

The above procedure proves that under Linux, the MMAP function can directly control the bottom layer without the driver.

I can only control the GPIO device on the Internet, and I have the ability to control other devices directly, pending verification.

Mmap Direct control of the bottom "turn"