Android Camera 五 Camera HAL v1

Android Camera 一源码路径

Android Camera 二 JNI JAVA和C/CPP图像数据传输流程分析

Android Camera 三 CameraService 和 Client 链接到 HAL

Android Camera 四 Camera HAL 分析

Linux v4l2 一应用层

Linux v4l2 二驱动和 usb 摄像头

Android硬件抽象层（Hardware Abstraction Layer，HAL）承上启下；

承上：连接camera framework 层APIs 。
启下：连接底层 Camera 驱动和硬件。

hardware/libhardware/include/hardware/camera.h

HAL API 接口声明

hardware/camera/capability_manager/CapabilityManager.cpp

camera 能力集管理，如曝光白平衡聚焦相机支持的图像格式等

hardware/camera/camera_hal/CameraHalImpl.cpp

camera hal 接口实现

hardware/camera/camera_hal/CameraHal.cpp

启下链接底层 camera 驱动和硬件

hardware/camera/camera_hal/CameraModule.cpp

承上 HAL module 注册

camera.h 定义了 HAL 的标准接口API ， HAL 层中代码实现并注册 camera.h 中声明的函数指针。

#ifndef ANDROID_INCLUDE_CAMERA_H#define ANDROID_INCLUDE_CAMERA_H#include "camera_common.h"/** * Camera device HAL, initial version [ CAMERA_DEVICE_API_VERSION_1_0 ] * * DEPRECATED. New devices should use Camera HAL v3.2 or newer. * * Supports the android.hardware.Camera API, and the android.hardware.camera2 * API in legacy mode only. * * Camera devices that support this version of the HAL must return a value in * the range HARDWARE_DEVICE_API_VERSION(0,0)-(1,FF) in * camera_device_t.common.version. CAMERA_DEVICE_API_VERSION_1_0 is the * recommended value. * * Camera modules that implement version 2.0 or higher of camera_module_t must * also return the value of camera_device_t.common.version in * camera_info_t.device_version. * * See camera_common.h for more details. */__BEGIN_DECLSstruct camera_memory;typedef void (*camera_release_memory)(struct camera_memory *mem);typedef struct camera_memory{    void *data;    size_t size;    void *handle;    camera_release_memory release;} camera_memory_t;typedef camera_memory_t* (*camera_request_memory)(int fd, size_t buf_size, unsigned int num_bufs,        void *user);typedef void (*camera_notify_callback)(int32_t msg_type,                                       int32_t ext1,                                       int32_t ext2,                                       void *user);typedef void (*camera_data_callback)(int32_t msg_type,                                     const camera_memory_t *data, unsigned int index,                                     camera_frame_metadata_t *metadata, void *user);typedef void (*camera_data_timestamp_callback)(int64_t timestamp,        int32_t msg_type,        const camera_memory_t *data, unsigned int index,        void *user);#define HAL_CAMERA_PREVIEW_WINDOW_TAG 0xcafed00dtypedef struct preview_stream_ops{    int (*dequeue_buffer)(struct preview_stream_ops* w,                          buffer_handle_t** buffer, int *stride);    int (*enqueue_buffer)(struct preview_stream_ops* w,                          buffer_handle_t* buffer);    int (*cancel_buffer)(struct preview_stream_ops* w,                         buffer_handle_t* buffer);    int (*set_buffer_count)(struct preview_stream_ops* w, int count);    int (*set_buffers_geometry)(struct preview_stream_ops* pw,                                int w, int h, int format);    int (*set_crop)(struct preview_stream_ops *w,                    int left, int top, int right, int bottom);    int (*set_usage)(struct preview_stream_ops* w, int usage);    int (*set_swap_interval)(struct preview_stream_ops *w, int interval);    int (*get_min_undequeued_buffer_count)(const struct preview_stream_ops *w,                                           int *count);    int (*lock_buffer)(struct preview_stream_ops* w,                       buffer_handle_t* buffer);    int (*set_timestamp)(struct preview_stream_ops *w, int64_t timestamp);} preview_stream_ops_t;struct camera_device;typedef struct camera_device_ops{    /* 设置将预览帧发送到的活动窗口 */    int (*set_preview_window)(struct camera_device *,                              struct preview_stream_ops *window);    /* 设置通知和数据回调 */    void (*set_callbacks)(struct camera_device *,                          camera_notify_callback notify_cb,                          camera_data_callback data_cb,                          camera_data_timestamp_callback data_cb_timestamp,                          camera_request_memory get_memory,                          void *user);    void (*enable_msg_type)(struct camera_device *, int32_t msg_type);    void (*disable_msg_type)(struct camera_device *, int32_t msg_type);    int (*msg_type_enabled)(struct camera_device *, int32_t msg_type);    int (*start_preview)(struct camera_device *);    void (*stop_preview)(struct camera_device *);    /** 正在预览返回 true */    int (*preview_enabled)(struct camera_device *);    int (*store_meta_data_in_buffers)(struct camera_device *, int enable);    int (*start_recording)(struct camera_device *);    void (*stop_recording)(struct camera_device *);    int (*recording_enabled)(struct camera_device *);    void (*release_recording_frame)(struct camera_device *,                                    const void *opaque);    int (*auto_focus)(struct camera_device *);    int (*cancel_auto_focus)(struct camera_device *);    int (*take_picture)(struct camera_device *);    int (*cancel_picture)(struct camera_device *);    int (*set_parameters)(struct camera_device *, const char *parms);    char *(*get_parameters)(struct camera_device *);    void (*put_parameters)(struct camera_device *, char *);    int (*send_command)(struct camera_device *,                        int32_t cmd, int32_t arg1, int32_t arg2);    void (*release)(struct camera_device *);    int (*dump)(struct camera_device *, int fd);} camera_device_ops_t;typedef struct camera_device{    /**     * camera_device.common.version must be in the range     * HARDWARE_DEVICE_API_VERSION(0,0)-(1,FF). CAMERA_DEVICE_API_VERSION_1_0 is     * recommended.     */    hw_device_t common;    camera_device_ops_t *ops;    void *priv;} camera_device_t;__END_DECLS#endif /* #ifdef ANDROID_INCLUDE_CAMERA_H */

来看看 camera HAL 的注册：

把实现的回调函数注册到 camera.h 中声明的 struct camera_device_t 中

在 framework 中 CameraDevice.cpp 匹配 camera HAL 来操作相机硬件设备。

CameraDevice::CameraDevice(    sp module, const std::string& cameraId,    const SortedVector>& cameraDeviceNames) :        mModule(module),        mCameraId(cameraId),        mDisconnected(false),        mCameraDeviceNames(cameraDeviceNames)；

// hardware/camera/camera_hal/CameraModule.cpp/* 注册 camera 设备操作类方法 */static int camera_device_open(const hw_module_t* module, const char* name, hw_device_t** device){    CAMERA_HAL_LOGV("enter %s()", __FUNCTION__);    int ret         = 0;    int camera_id   = 0;    camera_device_t* camera_device              = NULL;    camera_device_ops_t* camera_ops             = NULL;    android::CameraHal* camera_hal   = NULL;    if(!name || !device)    {        ALOGE("invalid parameter[name=%p, device=%p]", name, device);        return -EINVAL;    }    camera_id  = atoi(name);    camera_hal = new android::CameraHal(camera_id);    if(!camera_hal || !camera_hal->mInitOK)    {        ALOGE("fail to allocate memory for CameraHal or fail to init CameraHal");        ret = -ENOMEM;        goto EXIT;        //return -EINVAL;    }    camera_device   = new camera_device_t;    camera_ops      = new camera_device_ops_t;    if(!camera_device || !camera_ops)    {        ALOGE("fail to allocate memory for camera_device_t or camera_device_ops_t");        ret = -ENOMEM;        goto EXIT;    }    memset(camera_device, 0x00, sizeof(*camera_device));    memset(camera_ops, 0x00, sizeof(*camera_ops));/* 注册回调函数 ，操作 camera */    camera_device->common.tag                 = HARDWARE_DEVICE_TAG;    camera_device->common.version             = 0;    camera_device->common.module              = const_cast(module);    camera_device->common.close               = camera_device_close;    camera_device->ops                        = camera_ops;    camera_device->priv                       = camera_hal;    camera_ops->set_preview_window            = set_preview_window;    camera_ops->set_callbacks                 = set_callbacks;    camera_ops->auto_focus                    = auto_focus;    camera_ops->enable_msg_type               = enable_msg_type;    camera_ops->disable_msg_type              = disable_msg_type;    camera_ops->msg_type_enabled              = msg_type_enabled;    camera_ops->start_preview                 = start_preview;    camera_ops->stop_preview                  = stop_preview;    camera_ops->preview_enabled               = preview_enabled;    camera_ops->store_meta_data_in_buffers    = store_meta_data_in_buffers;    camera_ops->start_recording               = start_recording;    camera_ops->stop_recording                = stop_recording;    camera_ops->recording_enabled             = recording_enabled;    camera_ops->release_recording_frame       = release_recording_frame;    camera_ops->cancel_auto_focus             = cancel_auto_focus;    camera_ops->take_picture                  = take_picture;    camera_ops->cancel_picture                = cancel_picture;    camera_ops->set_parameters                = set_parameters;    camera_ops->get_parameters                = get_parameters;    camera_ops->put_parameters                = put_parameters;    camera_ops->send_command                  = send_command;    camera_ops->release                       = release;    camera_ops->dump                          = dump;    *device                                   = &camera_device->common;    return 0;EXIT:    if(camera_hal)    {        delete camera_hal;        camera_hal = NULL;    }    if(camera_device)    {        delete camera_device;        camera_device = NULL;    }    if(camera_ops)    {        delete camera_ops;        camera_ops = NULL;    }    return -1;}/*  camera hardware module methods */static struct hw_module_methods_t camera_module_methods ={open : camera_device_open};/*  externel interface for camera service *//* 注册 HAL 必须实现的字段 */struct camera_module HAL_MODULE_INFO_SYM ={common:    {tag                 : HARDWARE_MODULE_TAG,        version_major       : 1,        version_minor       : 0,id                  : CAMERA_HARDWARE_MODULE_ID,name                : "Camera module",author              : "xxxxxx",methods             : &camera_module_methods,dso                 : NULL,reserved            : {0},    },get_number_of_cameras   :camera_get_number_of_cameras,get_camera_info         :camera_get_camera_info,};

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