基于TINY4412的Andorid开发-------简单的LED灯控制

Posted 2020-09-26 请给我倒杯茶

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本文转载自：http://www.cnblogs.com/pengdonglin137/p/3857724.html

基于TINY4412的Andorid开发-------简单的LED灯控制

阅读目录(Content)

参考资料：

《Andriod系统源代码情景分析》

《嵌入式Linux系统开发完全手册_基于4412_上册》

作者：彭东林

邮箱：pengdonglin137@163.com

平台介绍：

主机：Win7 32位

虚拟机：VMware10 + ubuntu-12.04.2-desktop-amd64

android版本: android-4.2.2_r1

Linux内核版本：linux-3.5.0

Bootloader: 友善之臂提供的Superboot4412.bin

目标平台：tiny4412ADK+S700 4GB Flash

目的：在Tiny4412上运行的Android系统上，通过点击屏幕上的Button来控制Tiny4412的核心板上的四个LED灯的亮灭。一个有八个Button，每个灯的亮灭通过两个灯来控制，点击ON，相应的LED亮；点击OFF，相应的LED灯灭。

下面分几步完成：

1、编写驱动程序

2、测试驱动程序

3、编写HAL代码

4、编写framework代码

5、编写JNI代码

6、编写App

下面开始：

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一、编写驱动程序

分析tiny4412的原理图，看一下LED灯的位置：

可以知道，LED是低电平亮，高电平灭。

看一下，接到了Exynos4412的哪些引脚上了：

可以看到：

LED1 --------- GPM4_0

LED2 --------- GPM4_1

LED3 --------- GPM4_2

LED4 --------- GPM4_3

看一下Exynos4412的芯片手册，看一下GPM4的相关寄存器：

图中第二列表示的相对于基地址的偏移量，这里基地址是：0x11000000.

在芯片手册的Page288 ~ Page291对这些寄存器有更详细的介绍。

以GPM4_0引脚为例：

为了控制灯，[3:0]应设置为0x01，即输出模式

向GPM4DAT的第0位写0，GPM4_0引脚输出低电平，LED1亮；

向GPM4DAT的第0位写1，GPM4_0引脚输出高电平，LED1灭；

接下来，开始写驱动程序，用友善之臂自带的Linux3.5.0内核

   1:  cd linux-3.5/

   2:  cd drivers/

   3:  mkdir android_led

   4:  cd android_led/

在android_led/下创建led_demo.c和led_demo.h文件：

touch  led_demo.c led_demo.h

再在其中创建Makefile和Kconfig文件

touch Makefile Kconfig

修改Kconfig:

   1:  config LED_DEMO

   2:      tristate "Android Led Demo"

   3:      default n

   4:      help

   5:      This is the led demo for Android system.

修改Makefile:

obj-$(CONFIG_LED_DEMO) += led_demo.o

修改drivers/Kconfig，添加 source “drivers/android_led/Kconfig”

   1:  menu "Device Drivers"

2:

   3:  source "drivers/android_led/Kconfig"

4:

   5:  ......

6:

   7:  endmenu

修改drivers/Makefile:

   1:  ......

2:

   3:  obj-$(CONFIG_LED_DEMO)  += android_led/

在内核顶层目录下执行make menuconfig，进入Device Drivers，将 Android Led Demo选择为*，然后保存配置退出。

注：执行上面这些操作之前，确保已经按照友善之臂的手册，成功编译了Android上用的Linux内核，并且在arch/arm/boot下生成了zImage等文件。

在前期开发的时候，时不时要编译，可以将drivers/android_led/Makefile修改为：

   1:  #obj-$(CONFIG_LED_DEMO) += led_demo.o

   2:  obj-m += led_demo.o

编译的时候，可以使用：

make M=drivers/android_led modules

目的是提高编译速度,最后再将Makfile改回原样。临时测试，可以在Wind7的命令行下，使用adb push将led_demo.ko上传到/data/local下，然后用adb shell登陆板子，进行测试。

修改led_demo.h和led_demo.c

led_demo.h：

   1:  #ifndef __LED_DEMO_H__

   2:  #define __LED_DEMO_H__

3:

   4:  #include <linux/cdev.h>

5:

   6:  #define LED_ON    _IOW(\'L\', 0, int)

   7:  #define LED_OFF    _IOW(\'L\', 1, int)

8:

   9:  #define LED_DEMO_DEVICE_NODE_NAME  "led_demo"

  10:  #define LED_DEMO_DEVICE_CLASS_NAME "led_demo"

  11:  #define LED_DEMO_DEVICE_FILE_NAME  "led_demo"

12:

  13:  #define EXYNOS4412_GPM4CON    0x110002E0

  14:  #define EXYNOS4412_GPM4DAT    0x110002E4

15:

16:

  17:  struct led_demo_dev

  18:  {

  19:      struct cdev dev;

  20:  };

21:

  22:  #endif

led_demo.c：

   1:  #include <linux/kernel.h>

   2:  #include <linux/module.h>

   3:  #include <linux/fs.h>

   4:  #include <linux/slab.h>

   5:  #include <linux/device.h>

6:

   7:  #include <asm/io.h>

   8:  #include <asm/uaccess.h>

9:

10:

  11:  #include "led_demo.h"

12:

13:

  14:  MODULE_LICENSE("GPL");

15:

16:

  17:  static int led_demo_major;

  18:  static int led_demo_minor;

  19:  static int number_of_dev = 1;

20:

  21:  static struct led_demo_dev  *led_dev = NULL;

22:

  23:  static unsigned int *GPM4CON = NULL;

  24:  static unsigned int *GPM4DAT = NULL;

25:

  26:  static struct class *led_demo_class = NULL;

27:

28:

  29:  static int led_open (struct inode *node, struct file *fops)

  30:  {

  31:      struct led_demo_dev *dev;

32:

  33:      dev = container_of(node->i_cdev, struct led_demo_dev, dev);

34:

  35:      fops->private_data = dev;

36:

  37:      return 0;

  38:  }

  39:  static int led_close (struct inode *node, struct file *fops)

  40:  {

  41:      return 0;

  42:  }

43:

  44:  static long led_ioctl (struct file *fops, unsigned int cmd, unsigned long data)

  45:  {

  46:      //struct led_demo_dev * led_dev = (struct led_demo_dev *)fops->private_data;

47:

  48:      if((data < 1) || (data > 4))

  49:      {

  50:          printk(KERN_ALERT"parameter is no valid.\\n");

  51:          return -EINVAL;

  52:      }

53:

  54:      switch (cmd)

  55:      {

  56:          case LED_OFF:

  57:              writel(readl(GPM4DAT) | (0x1<<(data-1)), GPM4DAT);

  58:              break;

  59:          case LED_ON:

  60:              writel(readl(GPM4DAT) & ~(0x1<<(data-1)), GPM4DAT);

  61:              break;

  62:          default:

  63:              return -EINVAL;

  64:              break;

  65:      }

66:

67:

  68:      return 0;

  69:  }

70:

  71:  struct file_operations led_fops =

  72:  {

  73:      .owner = THIS_MODULE,

  74:      .open = led_open,

  75:      .unlocked_ioctl = led_ioctl,

  76:      .compat_ioctl = led_ioctl,

  77:      .release = led_close,

  78:  };

79:

  80:  static int __led_setup_dev(struct led_demo_dev * dev)

  81:  {

  82:      int err = -1;

83:

  84:      dev_t devno = MKDEV(led_demo_major, led_demo_minor);

85:

  86:      memset(dev, 0, sizeof(struct led_demo_dev));

87:

  88:      cdev_init(&(dev->dev), &led_fops);

89:

  90:      dev->dev.owner = THIS_MODULE;

91:

  92:      err = cdev_add(&(dev->dev), devno, number_of_dev);

  93:      if(err < 0)

  94:      {

  95:          return err;

  96:      }

97:

  98:      return 0;

  99:  }

 100:

 101:  static int led_demo_init(void)

 102:  {

 103:      int err = -1;

 104:      dev_t dev;

 105:      struct device *temp = NULL;

 106:

 107:      printk(KERN_ALERT"Initializing led demo device.\\n");

 108:

 109:      err = alloc_chrdev_region(&dev, 0, number_of_dev, LED_DEMO_DEVICE_NODE_NAME);

 110:      if(err < 0)

 111:      {

 112:          printk(KERN_ALERT"fail to alloc char dev region.\\n");

 113:          goto fail;

 114:      }

 115:

 116:      led_demo_major = MAJOR(dev);

 117:      led_demo_minor = MINOR(dev);

 118:

 119:      led_dev = kmalloc(sizeof(struct led_demo_dev), GFP_KERNEL);

 120:      if(!led_dev)

 121:      {

 122:          err = -ENOMEM;

 123:          printk(KERN_ALERT"Failed to alloc led device.\\n");

 124:          goto unregister;

 125:      }

 126:

 127:      err = __led_setup_dev(led_dev);

 128:      if (err < 0)

 129:      {

 130:          printk(KERN_ALERT"Failed to setup led device.\\n");

 131:          goto clean_up;

 132:      }

 133:

 134:      GPM4CON = (unsigned int *)ioremap(EXYNOS4412_GPM4CON, 4);

 135:      if(!GPM4CON)

 136:      {

 137:          err = -ENOMEM;

 138:          goto destroy_cdev;

 139:      }

 140:

 141:      GPM4DAT = (unsigned int *)ioremap(EXYNOS4412_GPM4DAT, 4);

 142:      if(!GPM4DAT)

 143:      {

 144:          err = -ENOMEM;

 145:          goto unmap1;

 146:      }

 147:

 148:      writel((readl(GPM4CON) & ~0xffff) | 0x1111, GPM4CON);

 149:      writel(readl(GPM4DAT)| 0xf, GPM4DAT);

 150:

 151:      led_demo_class = class_create(THIS_MODULE, LED_DEMO_DEVICE_CLASS_NAME);

 152:      if(IS_ERR(led_demo_class))

 153:      {

 154:          err = PTR_ERR(led_demo_class);

 155:          printk(KERN_ALERT"Failed to create led demo class.\\n");

 156:          goto unmap2;

 157:      }

 158:

 159:      temp = device_create(led_demo_class, NULL, dev, NULL, "%s", LED_DEMO_DEVICE_FILE_NAME);

 160:      if(IS_ERR(temp))

 161:      {

 162:          err = PTR_ERR(temp);

 163:          printk(KERN_ALERT"Failed to create led demo device.\\n");

 164:          goto destroy_class;

 165:      }

 166:

 167:      dev_set_drvdata(temp, (void *)led_dev);

 168:

 169:      printk(KERN_ALERT"Succeed to initialize led demo device.\\n");

 170:

 171:      return 0;

 172:

 173:  destroy_class:

 174:      class_destroy(led_demo_class);

 175:

 176:  unmap2:

 177:      iounmap(GPM4DAT);

 178:

 179:  unmap1:

 180:      iounmap(GPM4CON);

 181:

 182:  destroy_cdev:

 183:      cdev_del(&(led_dev->dev));

 184:

 185:  clean_up:

 186:      kfree(led_dev);

 187:

 188:  unregister:

 189:      unregister_chrdev_region(MKDEV(led_demo_major, led_demo_minor), number_of_dev);

 190:

 191:  fail:

 192:

 193:      return err;

 194:  }

 195:

 196:  static void led_demo_exit(void)

 197:  {

 198:      if(led_demo_class)

 199:      {

 200:          device_destroy(led_demo_class, MKDEV(led_demo_major, led_demo_minor));

 201:          class_destroy(led_demo_class);

 202:      }

 203:

 204:      iounmap(GPM4DAT);

 205:      iounmap(GPM4CON);

 206:

 207:      if(led_dev)

 208:      {

 209:          cdev_del(&(led_dev->dev));

 210:          kfree(led_dev);

 211:      }

 212:

 213:      unregister_chrdev_region(MKDEV(led_demo_major, led_demo_minor), number_of_dev);

 214:  }

 215:

 216:

 217:

 218:  module_init(led_demo_init);

 219:  module_exit(led_demo_exit);

 220:

编写完成后，在内核源码的顶层目录执行make zImage –jN，然后就会在arch/arm/boot/生成zImage文件，利用友善之臂提供的Minitools将zImage烧写到板子上。具体步骤，参考友善之臂提供的PDF文档：《Tiny4412用户手册》

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二、编写代码测试驱动程序

在android-4.2.2_r1源码顶层目录下

   1:  external/led_demo/

   2:  ├── Android.mk

   3:  ├── led_demo.c

   4:  └── led_demo.h

即，在external/下创建led_demo目录，并在其中创建Android.mk、led_demo.c以及led_demo.h文件.

Android.mk:

   1:  LOCAL_PATH:= $(call my-dir)

   2:  include $(CLEAR_VARS)

   3:  LOCAL_MODULE_TAGS := optional

   4:  LOCAL_SRC_FILES := $(call all-subdir-c-files)

   5:  LOCAL_MODULE := led_demo_test

   6:  include $(BUILD_EXECUTABLE)

7:

led_demo.h:

   1:  #ifndef __LED_DEMO_H__

   2:  #define __LED_DEMO_H__

3:

   4:  #define LED_ON    _IOW(\'L\', 0, int)

   5:  #define LED_OFF    _IOW(\'L\', 1, int)

6:

   7:  #endif

led_demo.c:

   1:  #include <stdio.h>

   2:  #include <sys/types.h>

   3:  #include <sys/stat.h>

   4:  #include <fcntl.h>

   5:  #include <stdlib.h>

   6:  #include <sys/ioctl.h>

7:

   8:  #include "led_demo.h"

9:

  10:  int main(int argc, const char *argv[])

  11:  {

  12:      int fd;

  13:      int i;

14:

  15:      fd = open("/dev/led_demo", O_RDWR);

  16:      if (fd < 0)

  17:      {

  18:          perror("failed to open.\\n");

  19:          exit(-1);

  20:      }

21:

  22:      while(1)

  23:      {

  24:          for(i=0; i<4; i++)

  25:          {

  26:              ioctl(fd, LED_OFF, i+1);

  27:              sleep(1);

  28:              ioctl(fd, LED_ON, i+1);

  29:              sleep(1);

  30:              ioctl(fd, LED_OFF, i+1);

  31:              sleep(1);

  32:          }

  33:      }

34:

  35:      close(fd);

36:

  37:      return 0;

  38:  }

编写完成后，在android-4.2.2_r1源码顶层目录下执行：

   1:    mmm ./external/led_demo/

2:

   3:   ./gen-img.sh

然后将顶层目录下新生成的system.img利用友善之臂提供的Minitools烧写到板子上。

烧写完成后，重启板子。

使用串口终端登陆板子，使用su命令进入root用户模式，然后进入/system/bin目录下，执行./led_demo_test，观察现象，可以看到，TINY4412的核心板上的四个LED灯循环亮灭。也可以使用wind7下的控制终端，用adb shell登陆板子，进行测试。

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三、编写HAL代码

在hardware/libhardware/include/hardware/下创建文件led_demo_hal.h

在hardware/libhardware/modules/下创建目录led_demo_hal，然后进入led_demo_hal，创建两个文件，分别是Android.mk和

led_demo_hal.cpp。

下面是文件内容：

hardware/libhardware/include/hardware/led_demo_hal.h

   1:  #ifndef ANDROID_LED_DEMO_HAL_H

   2:  #define ANDROID_LED_DEMO_HAL_H

3:

   4:  #include <hardware/hardware.h>

5:

   6:  __BEGIN_DECLS

7:

   8:  #define LED_DEMO_HARDWARE_MODULE_ID   "led_demo_hal"  //模块ID 需要与下面的Android.mk中的LOCAL_MODULE 匹配，否则无法加载该HAL模块

   9:  #define LED_DEMO_HARDWARE_DEVICE_ID   "led_demo"      // 设备ID

10:

11:

  12:  struct led_demo_module_t

  13:  {

  14:          struct hw_module_t common;

  15:  };

16:

  17:  struct led_demo_device_t

  18:  {

  19:          struct hw_device_t common;

  20:          int fd;

  21:          int (*set_on)(struct led_demo_device_t *dev, int val);  //用于控制LED，点亮第val个LED灯

  22:          int (*set_off)(struct led_demo_device_t *dev, int val); //熄灭第val个LED灯

  23:  };

24:

  25:  __END_DECLS

26:

27:

  28:  #endif

hardware/libhardware/modules/led_demo_hal/led_demo_hal.cpp

   1:  #define LOG_TAG "LED_DEMO_HALSTUB"   //将来可以用DDMS的LogCat工具进行调试，便于查看打印信息

2:

   3:  #include <hardware/hardware.h>

   4:  #include <hardware/led_demo_hal.h>

5:

   6:  #include <fcntl.h>

   7:  #include <errno.h>

8:

   9:  #include <utils/Log.h>

  10:  #include <cutils/atomic.h>

11:

12:

  13:  #define DEVICE_NAME    "/dev/led_demo"    //设备结点，有Linux驱动程序自动创建

  14:  #define MODULE_NAME    "led_demo"

  15:  #define MODULE_AUTHOR  "pengdonglin137@163.com"

16:

  17:  #define LED_ON  0x40044c00     //点灯的命令，其实就是_IOW(\'L\', 0, int)的值，_IOW在编译时无法识别，待以后解决

  18:  #define LED_OFF 0x40044c01     //灭灯命令，其实就是_IOW(\'L\', 1, int)的值，可以在上面的led_demo.c中加打印，看一下这个值是多少

19:

20:

  21:  static int led_demo_open(const struct hw_module_t* module, const char* id,

  22:          struct hw_device_t** device);

23:

  24:  static int led_demo_close(struct hw_device_t* device);

25:

  26:  static int led_demo_set_on(struct led_demo_device_t *dev, int val);

27:

  28:  static int led_demo_set_off(struct led_demo_device_t *dev, int val);

29:

30:

  31:  static hw_module_methods_t led_demo_module_methods =

  32:  {

  33:      open:led_demo_open,

  34:  };

35:

  36:  struct led_demo_module_t HAL_MODULE_INFO_SYM =

  37:  {

  38:      common:{

  39:          tag:HARDWARE_MODULE_TAG,

  40:          version_major:1,

  41:          version_minor:0,

  42:          id:LED_DEMO_HARDWARE_MODULE_ID,

  43:          name:MODULE_NAME,

  44:          author:MODULE_AUTHOR,

  45:          methods:&led_demo_module_methods,

  46:      }

  47:  };

48:

  49:  static int led_demo_open(const struct hw_module_t* module, const char* id,

  50:          struct hw_device_t** device)

  51:  {

  52:      if(!strcmp(id, LED_DEMO_HARDWARE_DEVICE_ID))

  53:      {

  54:          struct led_demo_device_t *dev;

55:

  56:          dev = (struct led_demo_device_t *)malloc(sizeof(struct led_demo_device_t));

  57:          if(!dev)

  58:          {

  59:              ALOGE("Failed to alloc space for struct led_demo_device_t.");

  60:              return -EFAULT;

  61:          }

62:

  63:          memset(dev, 0, sizeof(struct led_demo_device_t));

64:

  65:          dev->common.tag =

HARDWARE_DEVICE_TAG

  66:          dev->common.version = 0;

  67:          dev->common.module = (struct hw_module_t *)module;

  68:          dev->common.close = led_demo_close;

  69:          dev->set_on = led_demo_set_on;

  70:          dev->set_off = led_demo_set_off;

71:

  72:          if((dev->fd = open(DEVICE_NAME, O_RDWR)) == -1)

  73:          {

  74:              ALOGE("Failed to open device %s ---- %s\\n.", DEVICE_NAME, strerror(errno));

  75:              free(dev);

  76:              return -EFAULT;

  77:          }

78:

  79:          *device = &(dev->common);

80:

  81:          ALOGE("Open device file %s successfully.", DEVICE_NAME);

82:

  83:      }

84:

  85:      return -EFAULT;

  86:  }

87:

  88:  static int led_demo_close(struct hw_device_t* device)

  89:  {

  90:      struct led_demo_device_t *led_device = (struct led_demo_device_t *)device;

  91:      if(led_device)

  92:      {

  93:          close(led_device->fd);

  94:          free(led_device);

  95:      }

96:

  97:      return 0;

  98:  }

99:

 100:  static int led_demo_set_on(struct led_demo_device_t *dev, int val)

 101:  {

 102:      if(!dev)

 103:      {

 104:          ALOGE("Null dev pointer.");

 105:          return -EFAULT;

 106:      }

 107:

 108:      if(ioctl(dev->fd, LED_ON, val) < 0)

 109:      {

 110:          ALOGE("ioctl error --- %s.", strerror(errno));

 111:          return -EFAULT;

 112:      }

 113:

 114:      return 0;

 115:

 116:  }

 117:

 118:  static int led_demo_set_off(struct led_demo_device_t *dev, int val)

 119:  {

 120:      if(!dev)

 121:      {

 122:          ALOGE("Null dev pointer.");

 123:          return -EFAULT;

 124:      }

 125:

 126:      if(ioctl(dev->fd, LED_OFF, val) < 0)

 127:      {

 128:          ALOGE("ioctl error --- %s.", strerror(errno));

 129:          return -EFAULT;

 130:      }

 131:

 132:      return 0;

 133:

 134:  }

 135:

hardware/libhardware/modules/led_demo_hal/Android.mk

   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 := led_demo_hal.cpp

   8:  LOCAL_MODULE := led_demo_hal.default

   9:  include $(BUILD_SHARED_LIBRARY)

编写完成后，在Android源码的顶层目录执行：

mmm ./hardware/libhardware/modules/led_demo_hal/

最终out/target/product/tiny4412/system/lib/hw/目录下得到一个led_demo_hal.default.so文件。

下面处理一下硬件设备访问权限问题

在硬件抽象层模块中，我们是调用open函数来打开对应的设备文件的，在默认情况下，只有root用户才有权限访问系统的设备文件。但是一般的应用程序是没有root用户权限的。

解决办法，赋予root之外的其他用户访问设别文件/dev/led_demo的权限。做法如下：

在Android源码顶层目录下，修改system/core/rootdir/ueventd.rc，添加如下内容：

/dev/led_demo             0666   root       root

修改了ueventd.rc文件后，需要重新编译Android源代码工程，编译时，文件system/core/rootdir/ueventd.rc会拷贝到out/target/product/tiny4412/root/下，并且最终打包在ramdisk.img中。对于友善之臂，执行完make -jN后，还需要执行./gen-img.sh脚本，然后在Android源码顶层目录中会生成ramdisk-u.img文件，利用MiniTools将其烧写到板子上。

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四、编写Framework代码

定义硬件访问服务接口

在frameworks/base/core/java/android/os/创建文件ILed_demo_service.aidl，内容如下：

   1:  package android.os;

2:

   3:  interface ILed_demo_service

   4:  {

   5:      void led_set_ON(int val);

   6:      void led_set_OFF(int val);

   7:  }

然后，修改frameworks/base/Android.mk

   1:  LOCAL_SRC_FILES += \\

   2:      ......

   3:      core/java/android/os/IVibratorService.aidl \\

   4:      core/java/android/os/ILed_demo_service.aidl \\

最后，在Android源码顶层目录下执行

mmm ./frameworks/base/

编译后得到的framework.jar文件就包含了ILed_demo_service接口。

实现硬件访问服务

在frameworks/base/services/java/com/android/server/创建文件Led_demo_Service.java，内容如下：

   1:  package com.android.server;

   2:  import android.content.Context;

   3:  import android.os.ILed_demo_service;

   4:  import android.util.Slog;

5:

6:

   7:  public class Led_demo_Service extends ILed_demo_service.Stub

   8:  {

   9:          private static final String TAG = "Led_demo_Service";  //方便DDMS提供的LogCat工具看打印信息

10:

  11:          private int mPtr = 0;

12:

  13:          Led_demo_Service()

  14:          {

  15:                  mPtr = init_native();  //硬件访问服务Led_demo_Service在启动时，会通过JNI方法init_native

16:

  17:                  if(mPtr == 0)

  18:                  {

  19:                          Slog.e(TAG, "Failed to initialize Led demo Service.");

  20:                  }

  21:          }

22:

  23:          public void led_set_ON(int val)

  24:          {

  25:                  if(mPtr == 0)

  26:                  {

  27:                          Slog.e(TAG, "Led demo Service is not initialized.");

  28:                          return;

  29:                  }

30:

  31:                  set_ON_native(mPtr, val);

  32:          }

33:

  34:          public void led_set_OFF(int val)

  35:          {

  36:                  if(mPtr == 0)

  37:                  {

  38:                          Slog.e(TAG, "Led demo Service is not initialized.");

  39:                          return;

  40:                  }

41:

  42:                  set_OFF_native(mPtr, val);

  43:          }

44:

45:

  46:          private static native int init_native();

  47:          private static native void set_OFF_native(int mPtr, int val);

  48:          private static native void set_ON_native(int mPtr, int val);

49:

50:

  51:  };

编写完成后，在Android源码顶层目录下执行：

mmm ./frameworks/base/services/java/

编译后得到的services.jar文件就包含有Led_demo_Service类。

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五、编写JNI代码

在frameworks/base/services/jni/下创建文件com_android_server_led_demo_service.cpp，内容如下：

   1:  #define LOG_TAG  "LED_DEMO_Service_JNI"   //方便LogCat调试工具查看打印信息

2:

   3:  #include "jni.h"

   4:  #include "JNIHelp.h"

   5:  #include "android_runtime/AndroidRuntime.h"

6:

   7:  #include <utils/misc.h>

   8:  #include <utils/Log.h>

   9:  #include <hardware/hardware.h>

  10:  #include <hardware/led_demo_hal.h>

11:

  12:  #include <stdio.h>

13:

14:

  15:  namespace android

  16:  {

17:

  18:      static void led_demo_setOFF(JNIEnv *env, jobject clazz, jint ptr, jint value)

  19:      {

  20:          led_demo_device_t *device = (led_demo_device_t *)ptr;

  21:          if(!device)

  22:          {

  23:              ALOGE("Device led demo is not open.");

  24:              return ;

  25:          }

26:

  27:          int val = value;

28:

  29:          ALOGI("Set value %d to device led demo.", val);

30:

  31:          device->set_off(device, value);

  32:      }

33:

  34:      static void led_demo_setON(JNIEnv *env, jobject clazz, jint ptr, jint value)

  35:      {

  36:          led_demo_device_t *device = (led_demo_device_t *)ptr;

  37:          if(!device)

  38:          {

  39:              ALOGE("Device led demo is not open.");

  40:              return ;

  41:          }

42:

  43:          int val = value;

44:

  45:          ALOGI("Set value %d to device led demo.", val);

46:

  47:          device->set_on(device, value);

  48:      }

49:

50:

  51:      static inline int led_demo_device_open(const hw_module_t *module, struct led_demo_device_t **device)

  52:      {

  53:          return module->methods->open(module, LED_DEMO_HARDWARE_DEVICE_ID, (struct hw_device_t **)device);

  54:      }

55:

56:

57:

  58:      static jint led_demo_init(JNIEnv *env, jclass clazz)

  59:      {

  60:          struct led_demo_module_t *module;

  61:          struct led_demo_device_t *device;

62:

63:

  64:          ALOGI("Initializing HAL stub led ......");

65:

  66:          if(hw_get_module(

LED_DEMO_HARDWARE_MODULE_ID

, (const struct hw_module_t **)&module) == 0)

  67:          {

  68:              ALOGE("Device led demo found.");

69:

  70:              if(led_demo_device_open(&(module->common), &device))

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