自己动手 从android硬件驱动到APP－－－（2）hal驱动层

【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>>

1：aosp/hardware/libhardware/include/hardware/hello.h

#ifndef ANDROID_HELLO_INTERFACE_H
#define ANDROID_HELLO_INTERFACE_H
#include <hardware/hardware.h>

__BEGIN_DECLS
#define HELLO_HARDWARE_MODULE_ID "hello"//ID
struct hello_module_t {
    struct hw_module_t common;
};//hw_module_t的继承者
struct hello_device_t {
    struct hw_device_t common;
    int fd;
    int (*set_val)(struct hello_device_t* dev, int val);
    int (*get_val)(struct hello_device_t* dev, int* val);
};//hw_device_t的继承者
__END_DECLS

#endif

2：aosp/hardware/libhardware/modules/hello/hello.c

#define LOG_TAG "HelloStub"
#include <hardware/hardware.h>
#include <hardware/hello.h>

#include <sys/mman.h>

#include <dlfcn.h>

#include <cutils/ashmem.h>
#include <cutils/log.h>

#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <string.h>
#include <stdlib.h>

#include <cutils/log.h>
#include <cutils/atomic.h>

#define MODULE_NAME "Hello"
char const * const device_name = "/dev/hello" ;
static int hello_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device);
static int hello_device_close(struct hw_device_t* device);
static int hello_set_val(struct hello_device_t* dev, int val);
static int hello_get_val(struct hello_device_t* dev, int* val);

static struct hw_module_methods_t hello_module_methods = {
    .open = hello_device_open,
};
static int hello_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device)
{
    struct hello_device_t* dev;
    char name_[64];
    //pthread_mutex_t lock;
    dev = (struct hello_device_t*)malloc(sizeof(struct hello_device_t));
    if(!dev) {
        ALOGE("Hello Stub: failed to alloc space");
        return -EFAULT;
    }
    ALOGE("Hello Stub: hello_device_open eliot_shao");
    memset(dev, 0, sizeof(struct hello_device_t));

    dev->common.tag = HARDWARE_DEVICE_TAG;
    dev->common.version = 0;
    dev->common.module = (hw_module_t*)module;
    dev->common.close = hello_device_close;
    dev->set_val = hello_set_val;
    dev->get_val = hello_get_val;

    //pthread_mutex_lock(&lock);
    dev->fd = -1 ;
    snprintf(name_, 64, device_name, 0);
    dev->fd = open(name_, O_RDWR);
    if(dev->fd == -1) {
        ALOGE("Hello Stub:eliot failed to open %s !-- %s.", name_,strerror(errno));
        free(dev);
        return -EFAULT;
    }
    //pthread_mutex_unlock(&lock);
    *device = &(dev->common);
    ALOGI("Hello Stub: open HAL hello successfully.");
    return 0;
}

static int hello_device_close(struct hw_device_t* device) {
    struct hello_device_t* hello_device = (struct hello_device_t*)device;
    if(hello_device) {
        close(hello_device->fd);
        free(hello_device);
    }
    return 0;
}
static int hello_set_val(struct hello_device_t* dev, int val) {
    ALOGI("Hello Stub: set value to device.");
    write(dev->fd, &val, sizeof(val));
    return 0;
}
static int hello_get_val(struct hello_device_t* dev, int* val) {
    if(!val) {
        ALOGE("Hello Stub: error val pointer");
        return -EFAULT;
    }
    read(dev->fd, val, sizeof(*val));
    ALOGI("Hello Stub: get value  from device");
    return 0;
}

struct hello_module_t HAL_MODULE_INFO_SYM = {
    .common = {
        .tag                = HARDWARE_MODULE_TAG,
        //.module_api_version = FINGERPRINT_MODULE_API_VERSION_2_0,
        .hal_api_version    = HARDWARE_HAL_API_VERSION,
        .id                 = HELLO_HARDWARE_MODULE_ID,
        .name               = "Demo shaomingliang hello HAL",
        .author             = "The Android Open Source Project",
        .methods            = &hello_module_methods,
    },
};

来源：oschina

链接：https://my.oschina.net/u/2963604/blog/1784974