android平台led开发之硬件抽象层

二,硬件抽象层

 

1,在hardware\libhardware\include\hardware下新建swtled.h文件

swtled.h

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1. #ifndef ANDROID_SWTLED_INTERFACE_H
   
2. #define ANDROID_SWTLED_INTERFACE_H
   
3. 
   
4. #include <hardware/hardware.h>
   
5. 
   
6. __BEGIN_DECLS
   
7. 
   
8. //module interface
   
9. struct swtled_module_t
   
10. {
    
11.     struct hw_module_t common;
    
12. };
    
13. 
    
14. //device interface
    
15. struct swtled_device_t
    
16. {
    
17.     struct hw_device_t common;
    
18.     int fd;
    
19.     int (*set_on)(struct swtled_device_t* dev,int number);
    
20.     int (*set_off)(struct swtled_device_t* dev,int number);
    
21. };
    
22. 
    
23. 
    
24. #define SWTLED_HARDWARE_MODULE_ID "swtled"
    
25. __END_DECLS
    
26. 
    
27. #endif

2:在hardware/libhardware/module下新建swtled文件夹并新建swtled.c

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1. #define LOG_TAG "swtledStub"
   
2. 
   
3. #include <hardware/hardware.h>
   
4. #include <hardware/swtled.h>
   
5. #include <fcntl.h>
   
6. #include <errno.h>
   
7. #include <cutils/log.h>
   
8. #include <cutils/atomic.h>
   
9. #include <string.h>
   
10. #include <sys/types.h>
    
11. #include <sys/stat.h>
    
12. #include <sys/ioctl.h>
    
13. 
    
14. 
    
15. #define LED_ON _IO('k',1)
    
16. #define LED_OFF _IO('k',2)
    
17. 
    
18. #define DEVICE_NAME "/dev/swt_led"
    
19. #define MODULE_NAME "swtled"
    
20. #define MODULE_AUTHOR "zc"
    
21. 
    
22. 
    
23. 
    
24. //open or close device interface
    
25. 
    
26. static int swtled_device_open(const struct hw_module_t* module,const char* name, struct hw_device_t** device);
    
27. 
    
28. static int swtled_device_close(struct hw_device_t* device);
    
29. 
    
30. 
    
31. //light-on light-off
    
32. static int swtled_set_on(struct swtled_device_t* dev,int number);
    
33. static int swtled_set_off(struct swtled_device_t* dev,int number);
    
34. 
    
35. 
    
36. static int swtled_device_open(const struct hw_module_t* module,const char* name, struct hw_device_t** device)
    
37. {
    
38. 
    
39.     struct swtled_device_t * dev;
    
40.     dev = (struct swtled_device_t*)malloc(sizeof(struct swtled_device_t));
    
41.     if (!dev)
    
42.     {
    
43.      LOGE("Swtled Stub:failed to alloc space");
    
44.         return -EFAULT;
    
45.             
    
46.     }
    
47.     memset(dev,0,sizeof(struct swtled_device_t));
    
48.     dev->common.tag= HARDWARE_DEVICE_TAG;
    
49.     dev->common.version= 0;
    
50.     dev->common.module= (hw_module_t*)module;
    
51.     dev->common.close= swtled_device_close;
    
52.     dev->set_on= swtled_set_on;
    
53.     dev->set_off= swtled_set_off;
    
54. 
    
55.     if ((dev->fd= open(DEVICE_NAME,O_RDWR))== -1)
    
56.     {
    
57.         LOGE("Swtled Stub:failed to open /dev/swt_led -- %s.",strerror(errno));
    
58.         free(dev);
    
59.         return -EFAULT;
    
60.     }
    
61. 
    
62.     *device =&(dev->common);
    
63.     LOGI("Swtled Stub: open /dev/swt_led successfully");
    
64. 
    
65.     return 0;
    
66. }
    
67. 
    
68. static int swtled_device_close(struct hw_device_t* device)
    
69. {
    
70.     struct swtled_device_t* swtled_device = (struct swtled_device_t*)device;
    
71.     if (swtled_device)
    
72.     {
    
73.         close(swtled_device->fd);
    
74.         free(swtled_device);
    
75.     }
    
76.     return 0;
    
77. }
    
78. 
    
79. 
    
80. //------------------------------------------------------------------------------
    
81. //number: 1: light one 2:light two
    
82. //------------------------------------------------------------------------------
    
83. static int swtled_set_on(struct swtled_device_t* device,int number)
    
84. {
    
85.     ioctl(device->fd,LED_ON,number);
    
86.     return 0;
    
87. }
    
88. 
    
89. 
    
90. //------------------------------------------------------------------------------
    
91. //number: 1: light one 2:light two
    
92. //------------------------------------------------------------------------------
    
93. static int swtled_set_off(struct swtled_device_t* device,int number)
    
94. {
    
95.     ioctl(device->fd,LED_OFF,number);
    
96.     return 0;
    
97. }
    
98. 
    
99. 
    
100. 
     
101. //module method table
     
102. static struct hw_module_methods_t swtled_module_methods =
     
103. {
     
104.     open: swtled_device_open
     
105. };
     
106. 
     
107. 
     
108. 
     
109. const struct swtled_module_t HAL_MODULE_INFO_SYM= {
     
110. 
     
111.     common:
     
112.     {
     
113.         tag: HARDWARE_MODULE_TAG,
     
114.         version_major: 1,
     
115.         version_minor: 0,
     
116.         id: SWTLED_HARDWARE_MODULE_ID,
     
117.         name:MODULE_NAME,
     
118.         author: MODULE_AUTHOR,
     
119.         methods: &swtled_module_methods,        
     
120.     }
     
121.         
     
122. };

这里主要是通过hw_module_t和hw_device_t结构体形式将内核中led的驱动封装一层,
导出set_on和set_off接口,到时供JNI层的CPP调用。由于权限问题,应用层在打开dev时可能提示permission deny,所以需要修改
system\core\rootdir下的ueventd.rc文件,在其中添加一句

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1. /dev/swt_led 0666 root root

3,在同目录下添加Android.mk

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1. LOCAL_PATH := $(call my-dir)
2. include $(CLEAR_VARS)
3. LOCAL_MODULE_TAGS := optional
4. LOCAL_PRELINK_MODULE := false
5. LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw
6. LOCAL_SHARED_LIBRARIES := liblog
7. LOCAL_SRC_FILES := swtled.c
8. LOCAL_MODULE := swtled.default
9. include $(BUILD_SHARED_LIBRARY)

4,编译

 (1 进入到gingerbread目录下,执行mmm hardware/libhardware/modules/swtled会

    编译成功后，就可以在out/target/product/generic/system/lib/hw目录下看到swtled.default.so文件了

 

 (2 再执行make snod，使system.img镜像文件中包名硬件抽象模块swtled.default.so