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
Android Camera 五 Camera HAL v1
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_DECLS
struct 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 0xcafed00d
typedef 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,
};