Android 从上层到底层-----hal层

CPU：RK3288

系统：Android 5.1

功能：上层 app 控制 led 亮灭

开发板：Firefly RK3288

led_hal.c

path：hardware/rockchip/firefly/led_hal/led_hal.c

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <hardware/led_hal.h>

//日志的标签
#define LOG_TAG    "led_hal"
#include <utils/Log.h>

static int fd;

int led_hal_dev_close(struct hw_device_t *device)
{
    if(device != NULL)
    {
        struct led_hw_device_t *temp = (struct led_hw_device_t *)device;
        free(temp);
    }
    
    close(fd);
    
    return 0;
}

int led_hal_open_dev(void)
{
    ALOGD("--%s--", __func__);
    
    fd = open("/dev/firefly_leds", O_RDWR);
    if(fd < 0)
    {
        ALOGE("open failed : %s", strerror(errno));
        return fd;
    }
    
    return 0;
}

int led_hal_control_dev(int on)
{
    ALOGD("--%s--", __func__);
    
    int ret;
    
    ret = write(fd, &on, 4);
    if(ret < 0)
    {
        ALOGE("control failed : %s", strerror(errno));
        return ret;
    }
    
    return 0;
}

//该函数正确返回0
int led_hal_module_open(const struct hw_module_t *module, const char *id,
                        struct hw_device_t **device)
{
    ALOGD("--%s--", __func__);
    
    struct led_hw_device_t *led_dev = NULL;
    
    led_dev = (struct led_hw_device_t *)malloc(sizeof(struct led_hw_device_t));
    if (led_dev == NULL)
    {
        ALOGE("malloc failed");
        return -1;
    }
    
    ALOGD("malloc success");
    
    //初始化device对象
    led_dev->common.tag = HARDWARE_DEVICE_TAG;
    led_dev->common.version = 1;
    led_dev->common.module = module;
    led_dev->common.close = led_hal_dev_close;
    
    led_dev->open = led_hal_open_dev;
    led_dev->control = led_hal_control_dev;
    
    //将当前的led_dev传递给jni层
    *device = (struct hw_device_t *)led_dev;

    return 0;
}

struct hw_module_methods_t led_hal_methods = {
    open : led_hal_module_open,
};

//结构体名称必须为HMI
struct led_hw_module_t HMI = {
    common : {
        tag : HARDWARE_MODULE_TAG,
        version_major : 1,
        version_minor : 0,
        //id必须与jni层的一致
        id : LED_HAL_MODULE_ID,
        name : "firefly led hal module",
        methods : &led_hal_methods,
    },
};

led_hal.h

path：hardware/libhardware/include/hardware/led_hal.h

#ifndef _LED_HAL_H_
#define _LED_HAL_H_

#include <hardware/hardware.h>

#define LED_HAL_MODULE_ID    "firefly_led_hal"

//自定义module对象，一定要继承父类，
//可以扩展
struct led_hw_module_t {
    //一定要在结构体第一位，名称必须是common
    struct hw_module_t    common;
    //下面是扩展，用于测试
    int test；
};

//自定义device对象，一定要继承父类
//一定要扩展
struct led_hw_device_t {
    //一定要在结构体第一位，名称必须是common
    struct hw_device_t common;
    //下面为扩展
    int (*open)(void);
    int (*control)(int on);
};
#endif

Android.mk

path：hardware/rockchip/firefly/led_hal/led_hal.c

语法参照 Android.mk语法解析

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := firefly_led_hal.default
LOCAL_SRC_FILES := led_hal.c
LOCAL_LDLIBS    := -llog

LOCAL_MODULE_TAGS := optional
LOCAL_SHARED_LIBRARIES := liblog libcutils

LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw

include $(BUILD_SHARED_LIBRARY)

Android 从上层到底层-----kernel层

Android 从上层到底层-----jni层

Android 从上层到底层-----app层