QT5.5.1 嵌入式平台鼠标键盘不能热插拔问题解决（二）

爱被打了一巴掌 2022-07-15 06:13 980阅读 0赞

上一篇文章已经介绍了qt键鼠热插拔经历的曲折之路，这篇就具体解决热插拔问题。

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如上一篇文章所述，在源码中搜索了键鼠热插拔时的调试信息，

qt.qpa.input: Found mouse at "/dev/input/event0"  
qt.qpa.input: Found matching devices ("/dev/input/event0")  
qt.qpa.input: Adding mouse at "/dev/input/event0"  
qt.qpa.input: create mouse handler for "/dev/input/event0" ""  
qt.qpa.input: evdevtouch: Using device discovery

在QT\_ROOT/qtbase/src源码目录下搜索上述信息，在中断键入【grep -rn "Adding mouse at"】，结果如下

![20160519171418104][]

发现在QT\_ROOT/qtbase/src/platformsupport/input/evdevmouse/qevdevmousemanager.cpp文件中存在相应语句。从命名上就可以猜到该文件是用来管理mouse的，后续验证确实是。将相应的函数贴出来：

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1.  **void** QEvdevMouseManager::addMouse(**const** QString &deviceNode) 
2.  \{ 
3.   qCDebug(qLcEvdevMouse) << "Adding mouse at" << deviceNode; 
4.   QEvdevMouseHandler \*handler; 
5.   handler = QEvdevMouseHandler::create(deviceNode, m\_spec); 
6.  **if** (handler) \{ 
7.   connect(handler, SIGNAL(handleMouseEvent(**int**,**int**,**bool**,Qt::MouseButtons)), **this**, SLOT(handleMouseEvent(**int**,**int**,**bool**,Qt::MouseButtons))); 
8.   connect(handler, SIGNAL(handleWheelEvent(**int**,Qt::Orientation)), **this**, SLOT(handleWheelEvent(**int**,Qt::Orientation))); 
9.   m\_mice.insert(deviceNode, handler); 
10.  QInputDeviceManagerPrivate::get(QGuiApplicationPrivate::inputDeviceManager())->setDeviceCount( 
11.  QInputDeviceManager::DeviceTypePointer, m\_mice.count()); 
12.  \} **else** \{ 
13.  qWarning("evdevmouse: Failed to open mouse device %s", qPrintable(deviceNode)); 
14.  \} 
15. \}

在同一个文件中的类函数中（贴出部分，如下）可以看出该函数是用于接收信号的槽，且信号为deviceDetected

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1.  。。。。 
2.  
3.   qCDebug(qLcEvdevMouse) << "evdevmouse: Using device discovery"; 
4.   m\_deviceDiscovery = QDeviceDiscovery::create(QDeviceDiscovery::Device\_Mouse | QDeviceDiscovery::Device\_Touchpad, **this**); 
5.  **if** (m\_deviceDiscovery) \{ 
6.  // scan and add already connected keyboards
7.   QStringList devices = m\_deviceDiscovery->scanConnectedDevices(); 
8.   foreach (**const** QString &device, devices) \{ 
9.   addMouse(device); 
10.  \} 
11. 
12.  connect(m\_deviceDiscovery, SIGNAL(deviceDetected(QString)), **this**, SLOT(addMouse(QString))); 
13.  connect(m\_deviceDiscovery, SIGNAL(deviceRemoved(QString)), **this**, SLOT(removeMouse(QString))); 
14.  \} 
15.  。。。。

同理还存在另外一对信号与槽，全部列举出来：

SIGNAL(deviceDetected(QString)) —— SLOT(addMouse(QString))  
SIGNAL(deviceRemoved(QString))—— SLOT(removeMouse(QString))

这两对函数正如猜测的那样，是udev管理热插拔时发出的，具体的发出位置可以搜索【grep -rn "deviceDetected"】 ，结果如下：

![20160519172601109][]

发现在名为qdevicediscovery\_udev.cpp的文件中进行的信号发送工作：emit deviceDetected(devNode);

打开qdevicediscovery\_udev.cpp所在路径的devicediscovery.pri文件，内容如下：

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1.  HEADERS += $$PWD/qdevicediscovery\_p.h 
2.  
3.  linux \{ 
4.   contains(QT\_CONFIG, libudev) \{ 
5.   SOURCES += $$PWD/qdevicediscovery\_udev.cpp 
6.   HEADERS += $$PWD/qdevicediscovery\_udev\_p.h 
7.   INCLUDEPATH += $$QMAKE\_INCDIR\_LIBUDEV 
8.   LIBS\_PRIVATE += $$QMAKE\_LIBS\_LIBUDEV 
9.   \} **else**: contains(QT\_CONFIG, evdev) \{ 
10.  SOURCES += $$PWD/qdevicediscovery\_static.cpp 
11.  HEADERS += $$PWD/qdevicediscovery\_static\_p.h 
12.  \} **else** \{ 
13.  SOURCES += $$PWD/qdevicediscovery\_dummy.cpp 
14.  HEADERS += $$PWD/qdevicediscovery\_dummy\_p.h 
15.  \} 
16. \} **else** \{ 
17.  SOURCES += $$PWD/qdevicediscovery\_dummy.cpp 
18. \}

移植过Linux的应该很眼熟，很明显是根据配置单进行选择编译的文件，由于没有配置libudev而默认配置了evdev，因此自动编译的文件名称为 qdevicediscovery\_static.cpp/.h。

思路与目标已经明确：

**1.在****qdevicediscovery\_static.cpp文件中实现检测键鼠插入与移除，并发送相应的信号deviceDetected/deviceRemoved即可。**  
**2.检测键鼠的插入与移除可以检测文件系统中/dev/input/目录下设备节点的变化，具体的监听采用QFileSystemWatcher类的路径监听（directoryChanged）。**

**一、添加监听代码**

1.为了方便恢复，复制qdevicediscovery\_static.cpp和头文件为qdevicediscovery\_hotplug.cpp和qdevicediscovery\_hotplug\_p.h，修改文件中的static关键字为hotplug（强迫症，可不修改）。

2.由于需要保持监听长时存在，因此监听的实例声明要放在头文件中，并添加相应头文件，由于需要记住上一次添加的设备，因此仿造.cpp文件实现添加一个QStringList变量。

添加头文件：\#include <QFileSystemWatcher>

\#include <QStringList>

声明监听实例：QFileSystemWatcher \*m\_fileWatcher;

声明上一次添加设备的列表：QStringList m\_devices;  
声明信号函数：

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1.  **private** slots: 
2.  **void** handleHotPlugWatch(**const** QString &path);

3.初始化监听变量与信号监听函数实现

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1.  // 初始化文件监听器
2.  m\_fileWatcher = **new** QFileSystemWatcher(**this**); 
3.  m\_fileWatcher->addPath(QString::fromLatin1(QT\_EVDEV\_DEVICE\_PATH));// "dev/input/"
4.  connect(m\_fileWatcher, SIGNAL(directoryChanged(QString)), **this**, SLOT(handleHotPlugWatch(QString)));

信号监听函数实现

**\[cpp\]** [view plain][] [copy][view plain]

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1.  **void** QDeviceDiscoveryHotPlug::handleHotPlugWatch(**const** QString &path) 
2.  \{ 
3.  **if**(path.compare(QString::fromLatin1(QT\_EVDEV\_DEVICE\_PATH))) 
4.   \{ 
5.  **return**; 
6.   \} 
7.  
8.   QStringList devices; 
9.  
10. // 先移除原来的设备
11.  foreach (**const** QString &device, m\_devices) 
12.  deviceRemoved(device); 
13. 
14. // 获取现在的设备
15. // 注，这里获取的设备已经经过过滤，原因是在对该类进行实例化的时候
16. // 已经传进了筛选参数，如：QDeviceDiscovery::Device\_Keyboard
17.  devices = **this**\->scanConnectedDevices(); 
18. 
19. // 重新添加设备
20.  foreach (**const** QString &device, devices) 
21.  deviceDetected(device); 
22. \}

4.修改QStringList QDeviceDiscoveryHotPlug::scanConnectedDevices()函数，保存添加设备的列表

将QStringList devices;改成m\_devices.clear();，用以清除上一次的值

将该函数中的devices全部改成m\_devices，用以保存新的值。

**二、修改devicediscovery.pri文件中的编译选项**

如下：

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[![在CODE上查看代码片][CODE]][CODE_CODE] [![派生到我的代码片][ico_fork.svg]][ico_fork.svg 1]

1.  。。。 
2.   \} **else**: contains(QT\_CONFIG, evdev) \{ 
3.   SOURCES += $$PWD/qdevicediscovery\_hotplug.cpp 
4.   HEADERS += $$PWD/qdevicediscovery\_hotplug\_p.h 
5.   \} 
6.  。。。

修改文件完成后，重新make/make install，将安装后的qt文件移植到开发板上即可。现在QT5.5.1已经支持热插拔了～～～～

**附录：**修改后的qdevicediscovery\_hotplug.cpp和qdevicediscovery\_hotplug\_p.h文件如下

1.qdevicediscovery\_hotplug.cpp文件具体代码如下：

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1.  /\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*
2.  \*\*
3.  \*\* usb input device hot plug function
4.  \*\* by sn02241 
5.  \*\*
6.  \*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*/
7.  
8.  \#include "qdevicediscovery\_hotplug\_p.h"
9.  
10. \#include <QCoreApplication>
11. \#include <QObject>
12. \#include <QHash>
13. \#include <QDir>
14. \#include <QLoggingCategory>
15. \#include <QtCore/private/qcore\_unix\_p.h>
16. 
17. \#include <linux/input.h>
18. \#include <fcntl.h>
19. 
20. /\* android (and perhaps some other linux-derived stuff) don't define everything
21.  \* in linux/input.h, so we'll need to do that ourselves.
22.  \*/
23. \#ifndef KEY\_CNT
24. \#define KEY\_CNT (KEY\_MAX+1)
25. \#endif
26. \#ifndef REL\_CNT
27. \#define REL\_CNT (REL\_MAX+1)
28. \#endif
29. \#ifndef ABS\_CNT
30. \#define ABS\_CNT (ABS\_MAX+1)
31. \#endif
32. 
33. \#define LONG\_BITS (sizeof(long) \* 8 )
34. \#define LONG\_FIELD\_SIZE(bits) ((bits / LONG\_BITS) + 1)
35. 
36. **static****bool** testBit(**long** bit, **const****long** \*field) 
37. \{ 
38. **return** (field\[bit / LONG\_BITS\] >> bit % LONG\_BITS) & 1; 
39. \} 
40. 
41. QT\_BEGIN\_NAMESPACE 
42. 
43. Q\_LOGGING\_CATEGORY(lcDD, "qt.qpa.input") 
44. 
45. QDeviceDiscovery \*QDeviceDiscovery::create(QDeviceTypes types, QObject \*parent) 
46. \{ 
47. **return****new** QDeviceDiscoveryHotPlug(types, parent); 
48. \} 
49. 
50. QDeviceDiscoveryHotPlug::QDeviceDiscoveryHotPlug(QDeviceTypes types, QObject \*parent) 
51.  : QDeviceDiscovery(types, parent),m\_fileWatcher(0) 
52. \{ 
53. // 初始化文件监听器
54.  m\_fileWatcher = **new** QFileSystemWatcher(**this**); 
55.  m\_fileWatcher->addPath(QString::fromLatin1(QT\_EVDEV\_DEVICE\_PATH));// "dev/input/"
56.  connect(m\_fileWatcher, SIGNAL(directoryChanged(QString)), **this**, SLOT(handleHotPlugWatch(QString))); 
57. 
58.  qCDebug(lcDD) << "hotplug device discovery for type" << types; 
59. \} 
60. 
61. QStringList QDeviceDiscoveryHotPlug::scanConnectedDevices() 
62. \{ 
63.  m\_devices.clear(); 
64.  QDir dir; 
65.  dir.setFilter(QDir::System); 
66. 
67. // check for input devices
68. **if** (m\_types & Device\_InputMask) \{ 
69.  dir.setPath(QString::fromLatin1(QT\_EVDEV\_DEVICE\_PATH)); 
70.  foreach (**const** QString &deviceFile, dir.entryList()) \{ 
71.  QString absoluteFilePath = dir.absolutePath() + QString::fromLatin1("/") + deviceFile; 
72. **if** (checkDeviceType(absoluteFilePath)) 
73.  m\_devices << absoluteFilePath; 
74.  \} 
75.  \} 
76. 
77. // check for drm devices
78. **if** (m\_types & Device\_VideoMask) \{ 
79.  dir.setPath(QString::fromLatin1(QT\_DRM\_DEVICE\_PATH)); 
80.  foreach (**const** QString &deviceFile, dir.entryList()) \{ 
81.  QString absoluteFilePath = dir.absolutePath() + QString::fromLatin1("/") + deviceFile; 
82. **if** (checkDeviceType(absoluteFilePath)) 
83.  m\_devices << absoluteFilePath; 
84.  \} 
85.  \} 
86. 
87.  qCDebug(lcDD) << "Found matching devices" << m\_devices; 
88. 
89. **return** m\_devices; 
90. \} 
91. 
92. **bool** QDeviceDiscoveryHotPlug::checkDeviceType(**const** QString &device) 
93. \{ 
94. **bool** ret = **false**; 
95. **int** fd = QT\_OPEN(device.toLocal8Bit().constData(), O\_RDONLY | O\_NDELAY, 0); 
96. **if** (!fd) \{ 
97.  qWarning() << "Device discovery cannot open device" << device; 
98. **return****false**; 
99.  \} 
100. 
101. **long** bitsKey\[LONG\_FIELD\_SIZE(KEY\_CNT)\]; 
102. **if** (ioctl(fd, EVIOCGBIT(EV\_KEY, **sizeof**(bitsKey)), bitsKey) >= 0 ) \{ 
103. **if** (!ret && (m\_types & Device\_Keyboard)) \{ 
104. **if** (testBit(KEY\_Q, bitsKey)) \{ 
105.  qCDebug(lcDD) << "Found keyboard at" << device; 
106.  ret = **true**; 
107.  \} 
108.  \} 
109. 
110. **if** (!ret && (m\_types & Device\_Mouse)) \{ 
111. **long** bitsRel\[LONG\_FIELD\_SIZE(REL\_CNT)\]; 
112. **if** (ioctl(fd, EVIOCGBIT(EV\_REL, **sizeof**(bitsRel)), bitsRel) >= 0 ) \{ 
113. **if** (testBit(REL\_X, bitsRel) && testBit(REL\_Y, bitsRel) && testBit(BTN\_MOUSE, bitsKey)) \{ 
114.  qCDebug(lcDD) << "Found mouse at" << device; 
115.  ret = **true**; 
116.  \} 
117.  \} 
118.  \} 
119. 
120. **if** (!ret && (m\_types & (Device\_Touchpad | Device\_Touchscreen))) \{ 
121. **long** bitsAbs\[LONG\_FIELD\_SIZE(ABS\_CNT)\]; 
122. **if** (ioctl(fd, EVIOCGBIT(EV\_ABS, **sizeof**(bitsAbs)), bitsAbs) >= 0 ) \{ 
123. **if** (testBit(ABS\_X, bitsAbs) && testBit(ABS\_Y, bitsAbs)) \{ 
124. **if** ((m\_types & Device\_Touchpad) && testBit(BTN\_TOOL\_FINGER, bitsKey)) \{ 
125.  qCDebug(lcDD) << "Found touchpad at" << device; 
126.  ret = **true**; 
127.  \} **else****if** ((m\_types & Device\_Touchscreen) && testBit(BTN\_TOUCH, bitsKey)) \{ 
128.  qCDebug(lcDD) << "Found touchscreen at" << device; 
129.  ret = **true**; 
130.  \} **else****if** ((m\_types & Device\_Tablet) && (testBit(BTN\_STYLUS, bitsKey) || testBit(BTN\_TOOL\_PEN, bitsKey))) \{ 
131.  qCDebug(lcDD) << "Found tablet at" << device; 
132.  ret = **true**; 
133.  \} 
134.  \} 
135.  \} 
136.  \} 
137. 
138. **if** (!ret && (m\_types & Device\_Joystick)) \{ 
139. **long** bitsAbs\[LONG\_FIELD\_SIZE(ABS\_CNT)\]; 
140. **if** (ioctl(fd, EVIOCGBIT(EV\_ABS, **sizeof**(bitsAbs)), bitsAbs) >= 0 ) \{ 
141. **if** ((m\_types & Device\_Joystick) 
142.  && (testBit(BTN\_A, bitsKey) || testBit(BTN\_TRIGGER, bitsKey) || testBit(ABS\_RX, bitsAbs))) \{ 
143.  qCDebug(lcDD) << "Found joystick/gamepad at" << device; 
144.  ret = **true**; 
145.  \} 
146.  \} 
147.  \} 
148.  \} 
149. 
150. **if** (!ret && (m\_types & Device\_DRM) && device.contains(QString::fromLatin1(QT\_DRM\_DEVICE\_PREFIX))) 
151.  ret = **true**; 
152. 
153.  QT\_CLOSE(fd); 
154. **return** ret; 
155. \} 
156. 
157. **void** QDeviceDiscoveryHotPlug::handleHotPlugWatch(**const** QString &path) 
158. \{ 
159. **if**(path.compare(QString::fromLatin1(QT\_EVDEV\_DEVICE\_PATH))) 
160.  \{ 
161. **return**; 
162.  \} 
163. 
164.  QStringList devices; 
165. 
166. // 先移除原来的设备
167.  foreach (**const** QString &device, m\_devices) 
168.  deviceRemoved(device); 
169. 
170. // 获取现在的设备
171. // 注，这里获取的设备已经经过过滤，原因是在对该类进行实例化的时候
172. // 已经传进了筛选参数，如：QDeviceDiscovery::Device\_Keyboard
173.  devices = **this**\->scanConnectedDevices(); 
174. 
175. // 重新添加设备
176.  foreach (**const** QString &device, devices) 
177.  deviceDetected(device); 
178. \} 
179. 
180. QT\_END\_NAMESPACE

2.qdevicediscovery\_hotplug\_p.h文件具体代码如下：

**\[cpp\]** [view plain][] [copy][view plain]

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