• read(): This is the event interface. When the HID device performs an interrupt transfer, indicating a change of state, data will be made available at the associated hiddev device with the content of a struct hiddev_event:struct hiddev_event { unsigned hid; signed int value; };containing the HID usage identifier for the status that changed, and the value that it was changed to.
• ioctl(): This is the control interface. There are a number of controls:
  

  HIDIOCGVERSION	int (read)	Gets the version code out of the hiddev driver.
  HIDIOCAPPLICATION	(none)	This ioctl call returns the HID application usage associated with the hid device. The third argument to ioctl() specifies which application index to get. This is useful when the device has more than one application collection. If the index is invalid (greater or equal to the number of application collections this device has) the ioctl returns -1. You can find out beforehand how many application collections the device has from the num_applications field from the hiddev_devinfo structure.
  HIDIOCGDEVINFO	struct hiddev_devinfo (read)	Gets a hiddev_devinfo structure which describes the device.
  HIDIOCGSTRING	struct struct hiddev_string_descriptor (read/write)	Gets a string descriptor from the device. The caller must fill in the "index" field to indicate which descriptor should be returned.
  HIDIOCINITREPORT		Instructs the kernel to retrieve all input and feature report values from the device. At this point, all the usage structures will contain current values for the device, and will maintain it as the device changes.
  HIDIOCGNAME	string (variable length)	Gets the device name
  HIDIOCGREPORT	struct hiddev_report_info (write)	Instructs the kernel to get a feature or input report from the device, in order to selectively update the usage structures (in contrast to INITREPORT).
  HIDIOCSREPORT	struct hiddev_report_info (write)	Instructs the kernel to send a report to the device. This report can be filled in by the user throughHIDIOCSUSAGE calls (below) to fill in individual usage values in the report before sending the report in full to the device.
  HIDIOCGREPORTINFO	struct hiddev_report_info (read/write)	Fills in a hiddev_report_info structure for the user. The report is looked up by type (input, output or feature) and id, so these fields must be filled in by the user. The ID can be absolute -- the actual report id as reported by the device -- or relative -- HID_REPORT_ID_FIRST for the first report, and (HID_REPORT_ID_NEXT | report_id) for the next report after report_id. Without a-priori information about report ids, the right way to use this ioctl is to use the relative IDs above to enumerate the valid IDs. The ioctl returns non-zero when there is no more next ID. The real report ID is filled into the returned hiddev_report_info structure.
  HIDIOCGFIELDINFO	struct hiddev_field_info (read/write)	Returns the field information associated with a report in a hiddev_field_info structure. The user must fill in report_id and report_type in this structure, as above. The field_index should also be filled in, which should be a number from 0 and maxfield-1, as returned from a previous HIDIOCGREPORTINFO call.
  HIDIOCGUCODE	struct hiddev_usage_ref (read/write)	Returns the usage_code in a hiddev_usage_ref structure, given that given its report type, report id, field index, and index within the field have already been filled into the structure.
  HIDIOCGUSAGE	struct hiddev_usage_ref (read/write)	Returns the value of a usage in a hiddev_usage_ref structure. The usage to be retrieved can be specified as above, or the user can choose to fill in the report_type field and specify the report_id asHID_REPORT_ID_UNKNOWN. In this case, the hiddev_usage_ref will be filled in with the report and field infomation associated with this usage if it is found.
  HIDIOCSUSAGE	struct hiddev_usage_ref (write)	Sets the value of a usage in an output report.

write: Broken pipe

在内核 2.6.35以后进行了修正, 参考如下:

https://patchwork.kernel.org/patch/99990/

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1. /*
2. * Hidraw Userspace Example
3. *
4. * Copyright (c) 2010 Alan Ott <alan@signal11.us>
5. * Copyright (c) 2010 Signal 11 Software
6. *
7. * The code may be used by anyone for any purpose,
8. * and can serve as a starting point for developing
9. * applications using hidraw.
10. */
11. /* Linux */
12. #include <linux/types.h>
13. #include <linux/input.h>
14. #include <linux/hidraw.h>
15. /*
16. * Ugly hack to work around failing compilation on systems that don't
17. * yet populate new version of hidraw.h to userspace.
18. *
19. * If you need this, please have your distro update the kernel headers.
20. */
21. #ifndef HIDIOCSFEATURE
22. #define HIDIOCSFEATURE(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x06, len)
23. #define HIDIOCGFEATURE(len) _IOC(_IOC_WRITE|_IOC_READ, 'H', 0x07, len)
24. #endif
25. /* Unix */
26. #include <sys/ioctl.h>
27. #include <sys/types.h>
28. #include <sys/stat.h>
29. #include <fcntl.h>
30. #include <unistd.h>
31. /* C */
32. #include <stdio.h>
33. #include <string.h>
34. #include <stdlib.h>
35. #include <errno.h>
36. const char *bus_str(int bus);
37. int main(int argc, char **argv)
38. {
39. int fd;
40. int i, res, desc_size = 0;
41. char buf[256];
42. struct hidraw_report_descriptor rpt_desc;
43. struct hidraw_devinfo info;
44. /* Open the Device with non-blocking reads. In real life,
45. don't use a hard coded path; use libudev instead. */
46. fd = open("/dev/hidraw0", O_RDWR|O_NONBLOCK);
47. if (fd < 0) {
48. perror("Unable to open device");
49. return 1;
50. }
51. memset(&rpt_desc, 0x0, sizeof(rpt_desc));
52. memset(&info, 0x0, sizeof(info));
53. memset(buf, 0x0, sizeof(buf));
54. /* Get Report Descriptor Size */
55. res = ioctl(fd, HIDIOCGRDESCSIZE, &desc_size);
56. if (res < 0)
57. perror("HIDIOCGRDESCSIZE");
58. else
59. printf("Report Descriptor Size: %d\n", desc_size);
60. /* Get Report Descriptor */
61. rpt_desc.size = desc_size;
62. res = ioctl(fd, HIDIOCGRDESC, &rpt_desc);
63. if (res < 0) {
64. perror("HIDIOCGRDESC");
65. } else {
66. printf("Report Descriptor:\n");
67. for (i = 0; i < rpt_desc.size; i++)
68. printf("%hhx ", rpt_desc.value[i]);
69. puts("\n");
70. }
71. /* Get Raw Name */
72. res = ioctl(fd, HIDIOCGRAWNAME(256), buf);
73. if (res < 0)
74. perror("HIDIOCGRAWNAME");
75. else
76. printf("Raw Name: %s\n", buf);
77. /* Get Physical Location */
78. res = ioctl(fd, HIDIOCGRAWPHYS(256), buf);
79. if (res < 0)
80. perror("HIDIOCGRAWPHYS");
81. else
82. printf("Raw Phys: %s\n", buf);
83. /* Get Raw Info */
84. res = ioctl(fd, HIDIOCGRAWINFO, &info);
85. if (res < 0) {
86. perror("HIDIOCGRAWINFO");
87. } else {
88. printf("Raw Info:\n");
89. printf("\tbustype: %d (%s)\n",
90. info.bustype, bus_str(info.bustype));
91. printf("\tvendor: 0x%04hx\n", info.vendor);
92. printf("\tproduct: 0x%04hx\n", info.product);
93. }
94. /* Set Feature */
95. buf[0] = 0x9; /* Report Number */
96. buf[1] = 0xff;
97. buf[2] = 0xff;
98. buf[3] = 0xff;
99. res = ioctl(fd, HIDIOCSFEATURE(4), buf);
100. if (res < 0)
101. perror("HIDIOCSFEATURE");
102. else
103. printf("ioctl HIDIOCGFEATURE returned: %d\n", res);
104. /* Get Feature */
105. buf[0] = 0x9; /* Report Number */
106. res = ioctl(fd, HIDIOCGFEATURE(256), buf);
107. if (res < 0) {
108. perror("HIDIOCGFEATURE");
109. } else {
110. printf("ioctl HIDIOCGFEATURE returned: %d\n", res);
111. printf("Report data (not containing the report number):\n\t");
112. for (i = 0; i < res; i++)
113. printf("%hhx ", buf[i]);
114. puts("\n");
115. }
116. /* Send a Report to the Device */
117. buf[0] = 0x1; /* Report Number */
118. buf[1] = 0x77;
119. res = write(fd, buf, 2);
120. if (res < 0) {
121. printf("Error: %d\n", errno);
122. perror("write");
123. } else {
124. printf("write() wrote %d bytes\n", res);
125. }
126. /* Get a report from the device */
127. res = read(fd, buf, 16);
128. if (res < 0) {
129. perror("read");
130. } else {
131. printf("read() read %d bytes:\n\t", res);
132. for (i = 0; i < res; i++)
133. printf("%hhx ", buf[i]);
134. puts("\n");
135. }
136. close(fd);
137. return 0;
138. }
139. const char *
140. bus_str(int bus)
141. {
142. switch (bus) {
143. case BUS_USB:
144. return "USB";
145. break;
146. case BUS_HIL:
147. return "HIL";
148. break;
149. case BUS_BLUETOOTH:
150. return "Bluetooth";
151. break;
152. case BUS_VIRTUAL:
153. return "Virtual";
154. break;
155. default:
156. return "Other";
157. break;
158. }
159. }

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1. #if 1
2. ucNeedSend = 1;
3. Pos = HID_OFFSET_LENGTH + 1;
4. #if 0
5. ucSendData = 64;
6. for (i=0; i<ucSendData-2; i++)
7. SendBuffer[i+Pos] = 0x70 + i;
8. #else
9. ucSendData = RcvBuffer[HID_OFFSET_LENGTH];
10. for (i=0; i<ucSendData-2; i++)
11. SendBuffer[i+Pos] = RcvBuffer[i+Pos];
12. #endif
13. if (ucNeedSend) {
14. /* SendBuffer format
15. 1st byte     : ID_SEND_HID_RESPONSE
16. 2nd byte     : repply or error code flag
17. 3rd byte     : nb byte
18. others bytes: data
19. #define HID_SEND_HID_RESPONSE                0x07
20. #define HID_OFFSET                            0x00
21. #define HID_OFFSET_CMDCODE            HID_OFFSET + 1
22. #define HID_OFFSET_LENGTH                HID_OFFSET + 2
23. */
24. SendBuffer[HID_OFFSET] = HID_SEND_HID_RESPONSE;
25. //SendBuffer[HID_OFFSET_LENGTH] = MIN(HID_MAX_BUFFER_SIZE, SendBuffer[HID_OFFSET_LENGTH]);
26. SendBuffer[HID_OFFSET_LENGTH] = ucSendData;
27. /* Allows the transmission */
28. SetEPTxStatus(ENDP3, EP_TX_VALID);
29. USB_SIL_Write(EP3_IN, SendBuffer, HID_MAX_BUFFER_SIZE);
30. }