Linux USB HID gadget driver
1. Introduction
HID Gadget 驱动程序提供 USB 人机接口设备 (HID) 的仿真。 基本的 HID 处理在内核中完成，并且可以通过 /dev/hidgX 字符设备上的 I/O 发送/接收 HID 报告。
有关 HID 的更多详细信息，请参阅 https://www.usb.org/developers/hidpage/ 上的开发人员页面。
2. Configuration
g_hid 是一个平台驱动程序，因此要使用它，您需要将 struct platform_device(s) 添加到平台代码中，定义要使用的 HID 函数描述符 - 例如 就像是：
#include <linux/platform_device.h>
#include <linux/usb/g_hid.h>
/* hid descriptor for a keyboard */
static struct hidg_func_descriptor my_hid_data = {
.subclass = 0, /* No subclass */
.protocol = 1, /* Keyboard */
.report_length = 8,
.report_desc_length = 63,
.report_desc = {
0x05, 0x01, /* USAGE_PAGE (Generic Desktop) */
0x09, 0x06, /* USAGE (Keyboard) */
0xa1, 0x01, /* COLLECTION (Application) */
0x05, 0x07, /* USAGE_PAGE (Keyboard) */
0x19, 0xe0, /* USAGE_MINIMUM (Keyboard LeftControl) */
0x29, 0xe7, /* USAGE_MAXIMUM (Keyboard Right GUI) */
0x15, 0x00, /* LOGICAL_MINIMUM (0) */
0x25, 0x01, /* LOGICAL_MAXIMUM (1) */
0x75, 0x01, /* REPORT_SIZE (1) */
0x95, 0x08, /* REPORT_COUNT (8) */
0x81, 0x02, /* INPUT (Data,Var,Abs) */
0x95, 0x01, /* REPORT_COUNT (1) */
0x75, 0x08, /* REPORT_SIZE (8) */
0x81, 0x03, /* INPUT (Cnst,Var,Abs) */
0x95, 0x05, /* REPORT_COUNT (5) */
0x75, 0x01, /* REPORT_SIZE (1) */
0x05, 0x08, /* USAGE_PAGE (LEDs) */
0x19, 0x01, /* USAGE_MINIMUM (Num Lock) */
0x29, 0x05, /* USAGE_MAXIMUM (Kana) */
0x91, 0x02, /* OUTPUT (Data,Var,Abs) */
0x95, 0x01, /* REPORT_COUNT (1) */
0x75, 0x03, /* REPORT_SIZE (3) */
0x91, 0x03, /* OUTPUT (Cnst,Var,Abs) */
0x95, 0x06, /* REPORT_COUNT (6) */
0x75, 0x08, /* REPORT_SIZE (8) */
0x15, 0x00, /* LOGICAL_MINIMUM (0) */
0x25, 0x65, /* LOGICAL_MAXIMUM (101) */
0x05, 0x07, /* USAGE_PAGE (Keyboard) */
0x19, 0x00, /* USAGE_MINIMUM (Reserved) */
0x29, 0x65, /* USAGE_MAXIMUM (Keyboard Application) */
0x81, 0x00, /* INPUT (Data,Ary,Abs) */
0xc0 /* END_COLLECTION */
}
};
static struct platform_device my_hid = {
.name = "hidg",
.id = 0,
.num_resources = 0,
.resource = 0,
.dev.platform_data = &my_hid_data,
};
您可以根据需要添加任意数量的 HID 函数，仅受小工具驱动程序支持的中断端点数量的限制。
3. Configuration with configfs
如果 HID 是由 configfs 组成的小工具的一部分，则无需添加假平台设备和驱动程序来将某些数据传递到内核，而是通过将适当的字节流写入 configfs 属性来将 hidg_func_descriptor.report_desc 传递到内核。
4. Send and receive HID reports
可以使用 /dev/hidgX 字符设备上的读/写功能发送/接收 HID 报告。 请参阅下面的示例程序来执行此操作。
hid_gadget_test 是一个用于测试 HID 小工具驱动程序的小型交互式程序。 要使用，请将其指向 hidg 设备并设置设备类型（键盘/鼠标/操纵杆） - 例如：
# hid_gadget_test /dev/hidg0 keyboard
您现在处于 hid_gadget_test 的提示符下。 您可以键入选项和值的任意组合。 可用选项和值在程序启动时列出。 在键盘模式下，您最多可以发送六个值。
例如输入：g i s r –left-shift
按回车键，HID 小工具将发送相应的报告。
另一个有趣的例子是大写锁定测试。 输入 –caps-lock 并按回车键。 然后小工具会发送一份报告，您应该会收到主机答复，对应于大写锁定 LED 状态：
--caps-lock
recv report:2
使用此命令：
# hid_gadget_test /dev/hidg1 mouse
您可以测试鼠标模拟。 值是两个带符号的数字。
示例代码：
/* hid_gadget_test */
#include <pthread.h>
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define BUF_LEN 512
struct options {
const char *opt;
unsigned char val;
};
static struct options kmod[] = {
{.opt = "--left-ctrl", .val = 0x01},
{.opt = "--right-ctrl", .val = 0x10},
{.opt = "--left-shift", .val = 0x02},
{.opt = "--right-shift", .val = 0x20},
{.opt = "--left-alt", .val = 0x04},
{.opt = "--right-alt", .val = 0x40},
{.opt = "--left-meta", .val = 0x08},
{.opt = "--right-meta", .val = 0x80},
{.opt = NULL}
};
static struct options kval[] = {
{.opt = "--return", .val = 0x28},
{.opt = "--esc", .val = 0x29},
{.opt = "--bckspc", .val = 0x2a},
{.opt = "--tab", .val = 0x2b},
{.opt = "--spacebar", .val = 0x2c},
{.opt = "--caps-lock", .val = 0x39},
{.opt = "--f1", .val = 0x3a},
{.opt = "--f2", .val = 0x3b},
{.opt = "--f3", .val = 0x3c},
{.opt = "--f4", .val = 0x3d},
{.opt = "--f5", .val = 0x3e},
{.opt = "--f6", .val = 0x3f},
{.opt = "--f7", .val = 0x40},
{.opt = "--f8", .val = 0x41},
{.opt = "--f9", .val = 0x42},
{.opt = "--f10", .val = 0x43},
{.opt = "--f11", .val = 0x44},
{.opt = "--f12", .val = 0x45},
{.opt = "--insert", .val = 0x49},
{.opt = "--home", .val = 0x4a},
{.opt = "--pageup", .val = 0x4b},
{.opt = "--del", .val = 0x4c},
{.opt = "--end", .val = 0x4d},
{.opt = "--pagedown", .val = 0x4e},
{.opt = "--right", .val = 0x4f},
{.opt = "--left", .val = 0x50},
{.opt = "--down", .val = 0x51},
{.opt = "--kp-enter", .val = 0x58},
{.opt = "--up", .val = 0x52},
{.opt = "--num-lock", .val = 0x53},
{.opt = NULL}
};
int keyboard_fill_report(char report[8], char buf[BUF_LEN], int *hold)
{
char *tok = strtok(buf, " ");
int key = 0;
int i = 0;
for (; tok != NULL; tok = strtok(NULL, " ")) {
if (strcmp(tok, "--quit") == 0)
return -1;
if (strcmp(tok, "--hold") == 0) {
*hold = 1;
continue;
}
if (key < 6) {
for (i = 0; kval[i].opt != NULL; i++)
if (strcmp(tok, kval[i].opt) == 0) {
report[2 + key++] = kval[i].val;
break;
}
if (kval[i].opt != NULL)
continue;
}
if (key < 6)
if (islower(tok[0])) {
report[2 + key++] = (tok[0] - ('a' - 0x04));
continue;
}
for (i = 0; kmod[i].opt != NULL; i++)
if (strcmp(tok, kmod[i].opt) == 0) {
report[0] = report[0] | kmod[i].val;
break;
}
if (kmod[i].opt != NULL)
continue;
if (key < 6)
fprintf(stderr, "unknown option: %s\n", tok);
}
return 8;
}
static struct options mmod[] = {
{.opt = "--b1", .val = 0x01},
{.opt = "--b2", .val = 0x02},
{.opt = "--b3", .val = 0x04},
{.opt = NULL}
};
int mouse_fill_report(char report[8], char buf[BUF_LEN], int *hold)
{
char *tok = strtok(buf, " ");
int mvt = 0;
int i = 0;
for (; tok != NULL; tok = strtok(NULL, " ")) {
if (strcmp(tok, "--quit") == 0)
return -1;
if (strcmp(tok, "--hold") == 0) {
*hold = 1;
continue;
}
for (i = 0; mmod[i].opt != NULL; i++)
if (strcmp(tok, mmod[i].opt) == 0) {
report[0] = report[0] | mmod[i].val;
break;
}
if (mmod[i].opt != NULL)
continue;
if (!(tok[0] == '-' && tok[1] == '-') && mvt < 2) {
errno = 0;
report[1 + mvt++] = (char)strtol(tok, NULL, 0);
if (errno != 0) {
fprintf(stderr, "Bad value:'%s'\n", tok);
report[1 + mvt--] = 0;
}
continue;
}
fprintf(stderr, "unknown option: %s\n", tok);
}
return 3;
}
static struct options jmod[] = {
{.opt = "--b1", .val = 0x10},
{.opt = "--b2", .val = 0x20},
{.opt = "--b3", .val = 0x40},
{.opt = "--b4", .val = 0x80},
{.opt = "--hat1", .val = 0x00},
{.opt = "--hat2", .val = 0x01},
{.opt = "--hat3", .val = 0x02},
{.opt = "--hat4", .val = 0x03},
{.opt = "--hatneutral", .val = 0x04},
{.opt = NULL}
};
int joystick_fill_report(char report[8], char buf[BUF_LEN], int *hold)
{
char *tok = strtok(buf, " ");
int mvt = 0;
int i = 0;
*hold = 1;
/* set default hat position: neutral */
report[3] = 0x04;
for (; tok != NULL; tok = strtok(NULL, " ")) {
if (strcmp(tok, "--quit") == 0)
return -1;
for (i = 0; jmod[i].opt != NULL; i++)
if (strcmp(tok, jmod[i].opt) == 0) {
report[3] = (report[3] & 0xF0) | jmod[i].val;
break;
}
if (jmod[i].opt != NULL)
continue;
if (!(tok[0] == '-' && tok[1] == '-') && mvt < 3) {
errno = 0;
report[mvt++] = (char)strtol(tok, NULL, 0);
if (errno != 0) {
fprintf(stderr, "Bad value:'%s'\n", tok);
report[mvt--] = 0;
}
continue;
}
fprintf(stderr, "unknown option: %s\n", tok);
}
return 4;
}
void print_options(char c)
{
int i = 0;
if (c == 'k') {
printf(" keyboard options:\n"
" --hold\n");
for (i = 0; kmod[i].opt != NULL; i++)
printf("\t\t%s\n", kmod[i].opt);
printf("\n keyboard values:\n"
" [a-z] or\n");
for (i = 0; kval[i].opt != NULL; i++)
printf("\t\t%-8s%s", kval[i].opt, i % 2 ? "\n" : "");
printf("\n");
} else if (c == 'm') {
printf(" mouse options:\n"
" --hold\n");
for (i = 0; mmod[i].opt != NULL; i++)
printf("\t\t%s\n", mmod[i].opt);
printf("\n mouse values:\n"
" Two signed numbers\n"
"--quit to close\n");
} else {
printf(" joystick options:\n");
for (i = 0; jmod[i].opt != NULL; i++)
printf("\t\t%s\n", jmod[i].opt);
printf("\n joystick values:\n"
" three signed numbers\n"
"--quit to close\n");
}
}
int main(int argc, const char *argv[])
{
const char *filename = NULL;
int fd = 0;
char buf[BUF_LEN];
int cmd_len;
char report[8];
int to_send = 8;
int hold = 0;
fd_set rfds;
int retval, i;
if (argc < 3) {
fprintf(stderr, "Usage: %s devname mouse|keyboard|joystick\n",
argv[0]);
return 1;
}
if (argv[2][0] != 'k' && argv[2][0] != 'm' && argv[2][0] != 'j')
return 2;
filename = argv[1];
if ((fd = open(filename, O_RDWR, 0666)) == -1) {
perror(filename);
return 3;
}
print_options(argv[2][0]);
while (42) {
FD_ZERO(&rfds);
FD_SET(STDIN_FILENO, &rfds);
FD_SET(fd, &rfds);
retval = select(fd + 1, &rfds, NULL, NULL, NULL);
if (retval == -1 && errno == EINTR)
continue;
if (retval < 0) {
perror("select()");
return 4;
}
if (FD_ISSET(fd, &rfds)) {
cmd_len = read(fd, buf, BUF_LEN - 1);
printf("recv report:");
for (i = 0; i < cmd_len; i++)
printf(" %02x", buf[i]);
printf("\n");
}
if (FD_ISSET(STDIN_FILENO, &rfds)) {
memset(report, 0x0, sizeof(report));
cmd_len = read(STDIN_FILENO, buf, BUF_LEN - 1);
if (cmd_len == 0)
break;
buf[cmd_len - 1] = '\0';
hold = 0;
memset(report, 0x0, sizeof(report));
if (argv[2][0] == 'k')
to_send = keyboard_fill_report(report, buf, &hold);
else if (argv[2][0] == 'm')
to_send = mouse_fill_report(report, buf, &hold);
else
to_send = joystick_fill_report(report, buf, &hold);
if (to_send == -1)
break;
if (write(fd, report, to_send) != to_send) {
perror(filename);
return 5;
}
if (!hold) {
memset(report, 0x0, sizeof(report));
if (write(fd, report, to_send) != to_send) {
perror(filename);
return 6;
}
}
}
}
close(fd);
return 0;
}