在QT210 LDD的Android源碼樹中添加I2C讀寫工具（i2c-util）

通過/dev/i2c-n節點，用戶可以在userspace直接訪問板上的i2c外設寄存器，主要是透過I2C_RDWR這個IO控制命令將i2c_msg數組傳遞給kernel去執行。下面的代碼可以完成這個功能：

1. #include <stdio.h>
2. #include <linux/types.h>
3. #include <fcntl.h>
4. #include <unistd.h>
5. #include <stdlib.h>
6. #include <sys/types.h>
7. #include <sys/ioctl.h>
8. #include <errno.h>
9. #include <assert.h>
10. #include <string.h>
11. #include <linux/i2c.h>
13. /* This is the structure as used in the I2C_RDWR ioctl call */
14. struct i2c_rdwr_ioctl_data {
15. struct i2c_msg __user *msgs; /* pointers to i2c_msgs */
16. __u32 nmsgs; /* number of i2c_msgs */
17. };
19. int i2c_read_reg(char *dev, unsigned char *buf, unsigned slave_address, unsigned reg_address, int len)
20. {
21. struct i2c_rdwr_ioctl_data work_queue;
22. unsigned char w_val = reg_address;
23. int ret;
25. int fd = open(dev, O_RDWR);
26. if (!fd) {
27. printf("Error on opening the device file\n");
28. return 0;
29. }
31. work_queue.nmsgs = 2;
32. work_queue.msgs = (struct i2c_msg*)malloc(work_queue.nmsgs *sizeof(struct
33. i2c_msg));
34. if (!work_queue.msgs) {
35. printf("Memory alloc error\n");
36. close(fd);
37. return 0;
38. }
40. ioctl(fd, I2C_TIMEOUT, 2);
41. ioctl(fd, I2C_RETRIES, 1);
43. (work_queue.msgs[0]).len = 1;
44. (work_queue.msgs[0]).addr = slave_address;
45. (work_queue.msgs[0]).buf = &w_val;
47. (work_queue.msgs[1]).len = len;
48. (work_queue.msgs[1]).flags = I2C_M_RD;
49. (work_queue.msgs[1]).addr = slave_address;
50. (work_queue.msgs[1]).buf = buf;
52. ret = ioctl(fd, I2C_RDWR, (unsigned long) &work_queue);
53. if (ret < 0) {
54. printf("Error during I2C_RDWR ioctl with error code: %d\n", ret);
55. close(fd);
56. free(work_queue.msgs);
57. return 0;
58. } else {
59. printf("read salve:%02x reg:%02x\n", slave_address, reg_address);
60. close(fd);
61. free(work_queue.msgs);
62. return len;
63. }
64. }
66. int i2c_write_reg(char *dev, unsigned char *buf, unsigned slave_address, unsigned reg_address, int len)
67. {
68. struct i2c_rdwr_ioctl_data work_queue;
69. unsigned char w_val = reg_address;
70. unsigned char w_buf[len+1];
71. int ret;
73. w_buf[0] = reg_address;
75. int fd = open(dev, O_RDWR);
76. if (!fd) {
77. printf("Error on opening the device file\n");
78. return 0;
79. }
81. work_queue.nmsgs = 1;
82. work_queue.msgs = (struct i2c_msg*)malloc(work_queue.nmsgs *sizeof(struct
83. i2c_msg));
84. if (!work_queue.msgs) {
85. printf("Memory alloc error\n");
86. close(fd);
87. return 0;
88. }
90. ioctl(fd, I2C_TIMEOUT, 2);
91. ioctl(fd, I2C_RETRIES, 1);
93. (work_queue.msgs[0]).len = 1 + len;
94. (work_queue.msgs[0]).addr = slave_address;
95. (work_queue.msgs[0]).buf = w_buf;
97. memcpy(w_buf + 1, buf, len);
99. ret = ioctl(fd, I2C_RDWR, (unsigned long) &work_queue);
100. if (ret < 0) {
101. printf("Error during I2C_RDWR ioctl with error code: %d\n", ret);
102. close(fd);
103. free(work_queue.msgs);
104. return 0;
105. } else {
106. printf("write salve:%02x reg:%02x\n", slave_address, reg_address);
107. close(fd);
108. free(work_queue.msgs);
109. return len;
110. }
111. }
113. int main(int argc, char **argv)
114. {
115. unsigned int fd;
116. unsigned int slave_address, reg_address;
117. unsigned r_w;
118. unsigned w_val;
119. unsigned char rw_val;
121. if (argc < 5) {
122. printf("Usage:\n%s /dev/i2c-x start_addr reg_addr rw[0|1] [write_val]\n", argv[0]);
123. return 0;
124. }
126. fd = open(argv[1], O_RDWR);
128. if (!fd) {
129. printf("Error on opening the device file %s\n", argv[1]);
130. return 0;
131. }
133. sscanf(argv[2], "%x", &slave_address);
134. sscanf(argv[3], "%x", ®_address);
135. sscanf(argv[4], "%d", &r_w);
137. if (r_w == 0) {
138. i2c_read_reg(argv[1], &rw_val, slave_address, reg_address, 1);
139. printf("Read %s-%x reg %x, read value:%x\n", argv[1], slave_address, reg_address, rw_val);
140. } else {
141. if (argc < 6) {
142. printf("Usage:\n%s /dev/i2c-x start_addr reg_addr r|w[0|1] [write_val]\n", argv[0]);
143. return 0;
144. }
145. sscanf(argv[5], "%d", &w_val);
146. if ((w_val & ~0xff) != 0)
147. printf("Error on written value %s\n", argv[5]);
149. rw_val = (unsigned char)w_val;
150. i2c_write_reg(argv[1], &rw_val, slave_address, reg_address, 1);
151. }
153. return 0;
154. }

在Android/external/新建i2c-util目錄，上述源代碼存入android/external/i2c-util/i2c-util.c，編寫對應的Android.mk:

1. LOCAL_PATH := $(call my-dir)
2. include $(CLEAR_VARS)
4. LOCAL_MODULE_TAGS := optional
6. LOCAL_MODULE := i2c-util
8. LOCAL_SRC_FILES += \
9. i2c-util.c \
11. include $(BUILD_EXECUTABLE)

編譯Android後，上述工具會位於/system/bin目錄。在QT210 LDD上使用它：

[plain]

1. / # i2c-rw /dev/i2c-2 0x38 0x1 0
2. read salve:38 reg:01 value:12
3. / #
4. / # i2c-rw /dev/i2c-2 0x38 0x2 0
5. read salve:38 reg:02 value:81