S5PV210(TQ210)学习笔记——按键驱动程序

经过前面的配置，S5PV210开发已经可以成功进入Linux控制台了，那么，有了这个环境就可以开始学习Linux驱动的编写和测试了。学习Linux设备驱动，通常是从字符设备驱动开始。我写的第一个驱动程序是Led的，其实也就是熟悉下字符设备驱动的基本结构，本文以中断方式的按键驱动为例，简单的介绍下字符设备驱动程序。

一 按键驱动程序的简单实现

下面是基于中断和消息的按键驱动程序，其工作原理是：当应用程序读取键值时，会调用按键驱动程序的read函数，而我们实现的read函数检测完读取长度后没有直接读取键值而是等待按键消息，如果没有按键，程序会进入休眠状态，这样可以节省大量的CPU，而当我们按键时硬件会产生中断，程序自动进入中断处理函数，在中断处理函数中，驱动程序读取键值存入全局变量并激活read函数中等待的消息，应用程序被迅速唤醒并通过read函数读取键值，如此，完成了获取键值的工作。下面是源码，比较简单，也就不多说了。

源码：

1. #include
2. #include
3. #include
4. #include
5. #include
6. #include
7. #include
8. #include
9. #include
10. #include
11. #include
13. staticdev_tdevno;
14. staticstructcdevcdev;
15. staticstructclass*buttons_class;
16. staticstructdevice*buttons_device;
18. staticwait_queue_head_tbutton_waitq;
20. staticvolatileintpressed=0;
21. staticunsignedcharkey_val;
23. structkey_desc{
24. unsignedintpin;
25. unsignedcharvalue;
26. };
28. staticstructkey_desckey_descs[8]={
29. [0]={
30. .pin=S5PV210_GPH0(0),
31. .value=0x00,
32. },
34. [1]={
35. .pin=S5PV210_GPH0(1),
36. .value=0x01,
37. },
39. [2]={
40. .pin=S5PV210_GPH0(2),
41. .value=0x02,
42. },
44. [3]={
45. .pin=S5PV210_GPH0(3),
46. .value=0x03,
47. },
49. [4]={
50. .pin=S5PV210_GPH0(4),
51. .value=0x04,
52. },
54. [5]={
55. .pin=S5PV210_GPH0(5),
56. .value=0x05,
57. },
59. [6]={
60. .pin=S5PV210_GPH2(6),
61. .value=0x06,
62. },
64. [7]={
65. .pin=S5PV210_GPH2(7),
66. .value=0x07,
67. },
68. };
70. staticirqreturn_tbuttons_irq(intirq,void*dev_id){
71. volatilestructkey_desc*key=(volatilestructkey_desc*)dev_id;
73. if(gpio_get_value(key->pin)){
74. key_val=key->value|0x80;
75. }
76. else{
77. key_val=key->value;
78. }
80. pressed=1;
81. wake_up_interruptible(&button_waitq);
83. returnIRQ_RETVAL(IRQ_HANDLED);
84. }
86. staticintbuttons_open(structinode*inode,structfile*file){
87. intret;
89. ret=request_irq(IRQ_EINT(0),buttons_irq,IRQ_TYPE_EDGE_BOTH,"key1",&key_descs[0]);
90. if(ret)
91. returnret;
92. ret=request_irq(IRQ_EINT(1),buttons_irq,IRQ_TYPE_EDGE_BOTH,"key2",&key_descs[1]);
93. if(ret)
94. returnret;
95. ret=request_irq(IRQ_EINT(2),buttons_irq,IRQ_TYPE_EDGE_BOTH,"key3",&key_descs[2]);
96. if(ret)
97. returnret;
98. ret=request_irq(IRQ_EINT(3),buttons_irq,IRQ_TYPE_EDGE_BOTH,"key4",&key_descs[3]);
99. if(ret)
100. returnret;
101. ret=request_irq(IRQ_EINT(4),buttons_irq,IRQ_TYPE_EDGE_BOTH,"key5",&key_descs[4]);
102. if(ret)
103. returnret;
104. ret=request_irq(IRQ_EINT(5),buttons_irq,IRQ_TYPE_EDGE_BOTH,"key6",&key_descs[5]);
105. if(ret)
106. returnret;
107. ret=request_irq(IRQ_EINT(22),buttons_irq,IRQ_TYPE_EDGE_BOTH,"key7",&key_descs[6]);
108. if(ret)
109. returnret;
110. ret=request_irq(IRQ_EINT(23),buttons_irq,IRQ_TYPE_EDGE_BOTH,"key8",&key_descs[7]);
111. if(ret)
112. returnret;
113. return0;
114. }
116. staticssize_tbuttons_read(structfile*file,char__user*data,size_tcount,loff_t*loff){
117. if(count!=1){
118. printk(KERN_ERR"Thedrivercanonlygiveonekeyvalueonce!");
119. return-ENOMEM;
120. }
122. wait_event_interruptible(button_waitq,pressed);
123. pressed=0;
125. if(copy_to_user(data,&key_val,1)){
126. printk(KERN_ERR"Thedrivercannotcopythedatatouserarea!");
127. return-ENOMEM;
128. }
130. return0;
131. }
133. staticintbuttons_close(structinode*inode,structfile*file){
134. free_irq(IRQ_EINT(0),&key_descs[0]);
135. free_irq(IRQ_EINT(1),&key_descs[1]);
136. free_irq(IRQ_EINT(2),&key_descs[2]);
137. free_irq(IRQ_EINT(3),&key_descs[3]);
138. free_irq(IRQ_EINT(4),&key_descs[4]);
139. free_irq(IRQ_EINT(5),&key_descs[5]);
140. free_irq(IRQ_EINT(22),&key_descs[6]);
141. free_irq(IRQ_EINT(23),&key_descs[7]);
142. return0;
143. }
145. structfile_operationsbuttons_ops={
146. .open=buttons_open,
147. .read=buttons_read,
148. .release=buttons_close,
149. };
151. intbuttons_init(void){
152. intret;
154. cdev_init(&cdev,&buttons_ops);
155. cdev.owner=THIS_MODULE;
157. ret=alloc_chrdev_region(&devno,0,1,"buttons");
158. if(ret){
159. printk(KERN_ERR"allocchardeviceregionfaild!");
160. returnret;
161. }
163. ret=cdev_ad