一、原理分析
1. 首先通过打印usb_buf[i]中的8字节数据，看一下按键按下之后会接收到什么。
1）通过按完所有键盘按键打印的结果可知，有8个按键会打印在usb_buf[0]里，即：
ctrl左键----0x01----00000001
shift左键----0x02----00000010
alt左键----0x04------00000100
win左键----0x08-----00001000
ctrl右键----0x10------00010000
shift右键----0x20------00100000
alt右键----0x40--------01000000
win右键----0x80-------10000000
2）usb_buf[2]--usb_buf[7]为A B C D 1 2 3 4 F2 F4等普通的按键；
根据上节内容可知，按键的KEY_L等值得宏定义在input.h中，即：
从打印的usb_buf[i]数组可知，字符A为0x04，但alt左键也是0x04，该怎样在程序里区分呢？
。。。。。。。。。。
在键盘的源码程序/drivers/hid/usbhid/usbkbd.c中，使用过数组一一对应的：
static unsigned char usb_kbd_keycode[256] = {
0, 0, 0, 0, 30, 48, 46, 32, 18, 33, 34, 35, 23, 36, 37, 38,
50, 49, 24, 25, 16, 19, 31, 20, 22, 47, 17, 45, 21, 44, 2, 3,
4, 5, 6, 7, 8, 9, 10, 11, 28, 1, 14, 15, 57, 12, 13, 26,
27, 43, 43, 39, 40, 41, 51, 52, 53, 58, 59, 60, 61, 62, 63, 64,
65, 66, 67, 68, 87, 88, 99, 70,119,110,102,104,111,107,109,106,
105,108,103, 69, 98, 55, 74, 78, 96, 79, 80, 81, 75, 76, 77, 71,
72, 73, 82, 83, 86,127,116,117,183,184,185,186,187,188,189,190,
191,192,193,194,134,138,130,132,128,129,131,137,133,135,136,113,
115,114, 0, 0, 0,121, 0, 89, 93,124, 92, 94, 95, 0, 0, 0,
122,123, 90, 91, 85, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
29, 42, 56,125, 97, 54,100,126,164,166,165,163,161,115,114,113,
150,158,159,128,136,177,178,176,142,152,173,140
1）对于字符A的0x04就对应数组中的0x30；这里usb_buf[2-7]的0x04等数值，就对应usb_kbd_keycode[256]中的位置，确定每个按键的input码。
2）对于8个特殊按键，其位置为usb_buf[0]-1+ 224, input码为：usb_kbd_keycode[usb_buf[0]-1+ 224]（数组从0开始）。例如：ctrl左键在usb_buf[0]为0x01，对应的input码为：usb_kbd_keycode[0+ 224]=29。正好和input.h中的宏定义的值相同。
同时，也可以有源码程序推理出：
1 for (i = 0; i < 8; i++)
2 input_report_key(kbd->dev, usb_kbd_keycode[i + 224], (kbd->new[0] >> i) & 1);
程序中用于判断这8个按键的数据kbd->new[0]（usb_buf[0]）是否为1，然后通过input_report_key函数上传按键事件。
例如：alt左键----0x04------00000100按下后，判断(0x04 >> 2) & 1=1，则上报。
二、源码分析
1.中断函数
1 static void usb_kbd_irq(struct urb *urb)
3 struct usb_kbd *kbd = urb->context;
4 int i;
6 switch (urb->status) {
7 case 0: /* success */
8 break;
9 case -ECONNRESET: /* unlink */
10 case -ENOENT:
11 case -ESHUTDOWN:
12 return;
13
/* -EPIPE: should clear the halt */
14 default: /* error */
15 goto resubmit;
16 }
17 //特殊的8个按键检测是否按下
18 for (i = 0; i < 8; i++)
19 input_report_key(kbd->dev, usb_kbd_keycode[i + 224], (kbd->new[0] >> i) & 1);
20 //检测普通按键 数组下表为2-7
21 for (i = 2; i < 8; i++) {
22 //usb_kbd_keycode数组中跳过前面3个0，从3开始；
//上一次的按键kbd->old[i]非0数值 与 kbd->new + 2开始的6个字节的kbd->new[i]数组数值是否有相同的，若无，则按键已经松开
23 if (kbd->old[i] > 3 && memscan(kbd->new + 2, kbd->old[i], 6) == kbd->new + 8) {
24 if (usb_kbd_keycode[kbd->old[i]]) //判断非零值
25 input_report_key(kbd->dev, usb_kbd_keycode[kbd->old[i]], 0); //上传松开事件
26 else
27 info("Unknown key (scancode %#x) released.", kbd->old[i]);
28 }
29 //当前状态的按键kbd->new[i]非0数值 与 上一次的按键kbd->old[i]+ 2开始的6个字节的是否有相同的，若无，则按键已经按下
30 if (kbd->new[i] > 3 && memscan(kbd->old + 2, kbd->new[i], 6) == kbd->old + 8) {
31 if (usb_kbd_keycode[kbd->new[i]])
32 input_report_key(kbd->dev, usb_kbd_keycode[kbd->new[i]], 1);
33 else
34 info("Unknown key (scancode %#x) pressed.", kbd->new[i]);
35 }
36 }
38 input_sync(kbd->dev);
40 memcpy(kbd->old, kbd->new, 8); //拷贝当前按键的8个字节到kbd->old，进行下一次的判断
42 resubmit:
43 i = usb_submit_urb (urb, GFP_ATOMIC);
44 if (i)
45 err ("can't resubmit intr, %s-%s/input0, status %d",
46 kbd->usbdev->bus->bus_name,
47 kbd->usbdev->devpath, i);
2. 修改id_table（用于驱动和设备匹配的）
1 static struct usb_device_id usb_keyboardid_table [] = {
2 { USB_INTERFACE_INFO(USB_INTERFACE_CLASS_HID, USB_INTERFACE_SUBCLASS_BOOT,
3 USB_INTERFACE_PROTOCOL_KEYBOARD) },//USB协议:键盘协议
三、自己编写的程序
1 #include <linux/kernel.h>
2 #include <linux/slab.h>
3 #include <linux/module.h>
4 #include <linux/init.h>
5 #include <linux/usb/input.h>
6 #include <linux/hid.h>
8 static struct input_dev *myusb_kbd_dev;
9 static char *usb_buf;
10 static dma_addr_t usb_buf_phys;
11 static int len;
12 static struct urb *myusb_kbd_urb;
14 //键盘码表共有252个数据
15 static const unsigned char usb_kbd_keycode[252] = {
16 0, 0, 0, 0, 30, 48, 46, 32, 18, 33, 34, 35, 23, 36, 37, 38,
17 50, 49, 24, 25, 16, 19, 31, 20, 22, 47, 17, 45, 21, 44, 2, 3,
18 4, 5, 6, 7, 8, 9, 10, 11, 28, 1, 14, 15, 57, 12, 13, 26,
19 27, 43, 43, 39, 40, 41, 51, 52, 53, 58, 59, 60, 61, 62, 63, 64,
20 65, 66, 67, 68, 87, 88, 99, 70,119,110,102,104,111,107,109,106,
21 105,108,103, 69, 98, 55, 74, 78, 96, 79, 80, 81, 75, 76, 77, 71,
22 72, 73, 82, 83, 86,127,116,117,183,184,185,186,187,188,189,190,
23 191,192,193,194,134,138,130,132,128,129,131,137,133,135,136,113,
24 115,114, 0, 0, 0,121, 0, 89, 93,124, 92, 94, 95, 0, 0, 0,
25 122,123, 90, 91, 85, 0, 0, 0, 0, 0
, 0, 0, 0, 0, 0, 0,
26 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
27 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
28 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
29 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
30 29, 42, 56,125, 97, 54,100,126,164,166,165,163,161,115,114,113,
31 150,158,159,128,136,177,178,176,142,152,173,140
32 };
34 static struct usb_device_id usb_keyboardid_table [] = {
35 { USB_INTERFACE_INFO(USB_INTERFACE_CLASS_HID, USB_INTERFACE_SUBCLASS_BOOT,
36 USB_INTERFACE_PROTOCOL_KEYBOARD) },//USB协议:键盘协议
38 };
40 void my_memcpy(unsigned char *dest,unsigned char *src,int len) //复制缓存
41 {
42 while(len--)
43 {
44 *dest++= *src++;
45 }
46 }
48 static void usb_keyboardirq(struct urb *urb)
49 {
50 static unsigned char pre_val[8]={0,0,0,0,0,0,0,0};
51 int i;
53 //8个特殊按键，对比上一次的按键值pre_val[0]和当前usb_buf[0]，如果不相等有按键按下，则上报
54 for (i = 0; i < 8; i++)
55 if(((pre_val[0]>>i)&1)!=((usb_buf[0]>>i)&1))
56 {
57 input_report_key(myusb_kbd_dev, usb_kbd_keycode[i + 224], (usb_buf[0]>> i) & 1);
58 input_sync(myusb_kbd_dev); //上传同步事件
59 }
62 /*上传普通按键*/
63 for(i=2;i<8;i++)
64 if(pre_val[i]!=usb_buf[i]) //上一次和本次按键值不同，说明有按键按下
65 {
66 if(usb_buf[i]) //非0，按下事件上报
67 input_report_key(myusb_kbd_dev,usb_kbd_keycode[usb_buf[i]], 1);
68 else if(pre_val[i]) //上一次非零，本次为0，松开事件
69 input_report_key(myusb_kbd_dev,usb_kbd_keycode[pre_val[i]], 0);
70 input_sync(myusb_kbd_dev); //上传同步事件
71 }
73 my_memcpy(pre_val, usb_buf, 8); //更新数据
75 /* 重新提交urb */
76 usb_submit_urb(myusb_kbd_urb, GFP_KERNEL);
77 }
79 static int usb_keyboardprobe(struct usb_interface *intf, const struct usb_device_id *id)
80 {
81 volatile unsigned char i;
82 struct usb_device *dev = interface_to_usbdev(intf); //设备，通过usb_ interface接口获取usb_device设备,为后面设置USB数据传输用
83 struct usb_host_interface *interface; // 当前接口
84 struct usb_endpoint_descriptor *endpoint;
85 int pipe; //端点管道
87 interface = intf->cur_altsetting;
88 endpoint = &interface->endpoint[0].desc; //当前接口下的端点描述符
90 printk("VID=%x,PID=%x\n",dev->descriptor.idVendor,dev->descriptor.idProduct);
92 /* a. 分配一个input_dev */
93 myusb_kbd_dev = input_allocate_device();
95 /* b. 设置 */
96 /* b.1 能产生哪类事件 */
97 set_bit(EV_KEY, myusb_kbd_dev->evbit);
98 set_bit(EV_REP, myusb_kbd_dev->evbit);
100 /* b.2 添加所有按键 */
101 for (i = 0; i < 252; i++)
102 set_bit(usb_kbd_keycode[i], myusb_kbd_dev->keybit);
103 clear_bit(0, myusb_kbd_dev->keybit);
106 /* c. 注册 */
107 input_register_device(myusb_kbd_dev);
109 /* d. 硬件相关操作 */
110 /* 数据传输3要素: 源,目的,长度 */
111 /* 源: USB设备的某个端点 */
112 pipe = usb_rcvintpipe(dev, endpoint->bEndpointAddress);
114 /* 长度: */
115 len = endpoint->wMaxPacketSize;
117 /* 目的: */
118 usb_buf = usb_buffer_alloc(dev, len, GFP_ATOMIC, &usb_buf_phys);
120 /* 使用"3要素" */
121 /* 分配usb request block */
122 myusb_kbd_urb = usb_alloc_urb(0, GFP_KERNEL);//usb传输素具的urb结构体
123 /* 使用"3要素设置urb" */
124 usb_fill_int_urb(myusb_kbd_urb, dev, pipe, usb_buf, len, usb_keyboardirq, NULL, endpoint->bInterval);
125 myusb_kbd_urb->transfer_dma = usb_buf_phys;
126 myusb_kbd_urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
128 /* 使用URB */
129 usb_submit_urb(myusb_kbd_urb, GFP_KERNEL);
131 return 0;
132 }
134 static void usb_keyboarddisconnect(struct usb_interface *intf)
135 {
136 struct usb_device *dev = interface_to_usbdev(intf);
138 //printk("disconnect usbmouse!\n");
139 usb_kill_urb(myusb_kbd_urb);
140 usb_free_urb(myusb_kbd_urb);
142 usb_buffer_free(dev, len, usb_buf, usb_buf_phys);
143 input_unregister_device(myusb_kbd_dev);
144 input_free_device(myusb_kbd_dev);
145 }
147 /* 1. 分配/设置usb_driver */
148 static struct usb_driver usb_keyboarddriver = {
149 .name = "usb_keyboard",
150 .probe = usb_keyboardprobe,
151 .disconnect = usb_keyboarddisconnect,
152 .id_table = usb_keyboardid_table,
153 };
156 static int usb_keyboardinit(void)
157 {
158 /* 2. 注册 */
159 usb_register(&usb_keyboarddriver);
160 return 0;
161 }
163 static void usb_keyboardexit(void)
164 {
165 usb_deregister(&usb_keyboarddriver);
166 }
168 module_init(usb_keyboardinit);
169 module_exit(usb_keyboardexit);
171 MODULE_LICENSE("GPL");
1. 烧写内核，编译/加载驱动模块。
2. # cat /dev/tty1
3. # exec 0</dev/tty1 （直接可以用键盘操作开发板的控制台）
