高通Camx 架构学习笔记

和你一起终身学习，这里是程序员Android

经典好文推荐，通过阅读本文，您将收获以下知识点:

一、Camx 代码结构
二、Camx 编译
三、Camx 代码流程分析
四、Camx 调试

一、Camx 代码结构

目前主流的机型都使用camx架构，这个架构和之前架构的主要区别就是 芯片接口层的代码从hardware/qcom 迁移到 vendor/qcom/proprietary/下面，我们主要关注的camera hal层的源码也是放在vendor/qcom/proprietary/camx/下面。

1.1 camera 相关代码目录

二、camx 编译

camx的核心目录是 vendor/qcom/proprietary/camx/src/目录下面：

total 40
drwxrwxr-x 10 lxl lxl 4096  4月  4 10:52 ./
drwxrwxr-x  4 lxl lxl 4096  4月  4 10:52 ../
drwxrwxr-x  3 lxl lxl 4096  4月  4 10:52 chiiqutils/
drwxrwxr-x  7 lxl lxl 4096  4月  4 10:56 core/
drwxrwxr-x  7 lxl lxl 4096  4月  4 10:52 csl/
drwxrwxr-x 14 lxl lxl 4096  4月  4 10:52 hwl/
drwxrwxr-x  3 lxl lx 4096  4月  4 10:52 lib/
drwxrwxr-x  3 lxl lxl 4096  4月  4 10:52 osutils/
drwxrwxr-x 11 lxl lxl 4096  4月  4 10:52 swl/
drwxrwxr-x  3 lxl lxl 4096  4月  4 10:52 utils/

核心的Android.mk在 ./lib/build/android/Android.mk 中。
其中包括的静态库如下：

# Libraries to link
LOCAL_STATIC_LIBRARIES :=   \
    libcamxcore             \
    libcamxchi              \
    libcamxcsl              \
    libcamxofflinestats     \
    libnc                   \
    libcamxncs              \
    libifestriping          \
    libstriping

LOCAL_WHOLE_STATIC_LIBRARIES := \
    libcamxdspstreamer          \
    libcamxhwlbps               \
    libcamxgenerated            \
    libcamxhal                  \
    libcamxhalutils             \
    libcamxhwlfd                \
    libcamxhwlife               \
    libcamxhwlipe               \
    libcamxhwliqmodule          \
    libcamxswlfdmanager         \
    libcamxswljpeg              \
    libcamxhwljpeg              \
    libcamxhwllrme              \
    libcamxswlransac            \
    libcamxhwltitan17x          \
    libcamxiqsetting            \
    libcamxosutils              \
    libcamxstats                \
    libcamxsensor               \
    libcamxutils

这些静态库都是camx或者其他的目录下编译的，编译工程的时候，我们要先编译这些静态库，然后编译camx的动态库（/vendor/lib/hw/camera.qcom.so）。

三、camx 代码流程分析

camera.provider中如何实现到camera hal层的跳跃，camera service调用到camera provider中的接口方法，现在调用到 camera provider中的 hardware/interfaces/camera/device/3.2/default/CameraDeviceSession.cpp中的processCaptureRequest(...)方法，最终会调用到：

status_t ret = mDevice->ops->process_capture_request(mDevice, &halRequest);

这个mDevice->ops 就是 hardware/libhardware/include/hardware/camera3.h中的 camera3_device_ops 结构体： （参考：https://www.jianshu.com/p/099cc3b0ab25）

typedef struct camera3_device_ops {
    int (*initialize)(const struct camera3_device *,
            const camera3_callback_ops_t *callback_ops);
    int (*configure_streams)(const struct camera3_device *,
            camera3_stream_configuration_t *stream_list);
    int (*register_stream_buffers)(const struct camera3_device *,
            const camera3_stream_buffer_set_t *buffer_set);
    const camera_metadata_t* (*construct_default_request_settings)(
            const struct camera3_device *,
            int type);
    int (*process_capture_request)(const struct camera3_device *,
            camera3_capture_request_t *request);
    void (*get_metadata_vendor_tag_ops)(const struct camera3_device*,
            vendor_tag_query_ops_t* ops);
    void (*dump)(const struct camera3_device *, int fd);
    int (*flush)(const struct camera3_device *);
 
    /* reserved for future use */
    void *reserved[8];
} camera3_device_ops_t;

camera3_device_ops_t 映射函数指针操作： hardware/libhardware/modules/camera/3_0/Camera.cpp

const camera3_device_ops_t Camera::sOps = {
    .initialize = default_camera_hal::initialize,
    .configure_streams = default_camera_hal::configure_streams,
    .register_stream_buffers = default_camera_hal::register_stream_buffers,
    .construct_default_request_settings
        = default_camera_hal::construct_default_request_settings,
    .process_capture_request = default_camera_hal::process_capture_request,
    .get_metadata_vendor_tag_ops = NULL,
    .dump = default_camera_hal::dump,
    .flush = default_camera_hal::flush,
    .reserved = {0},
};

这样找到在camera hal层的函数指针的映射关系。
　　映射到：vendor/qcom/proprietary/camx/src/core/hal/camxhal3entry.cpp中的static Dispatch g_dispatchHAL3(&g_jumpTableHAL3);：

/// Array containing camera3_device_ops_t methods
static camera3_device_ops_t g_camera3DeviceOps =
{
    CamX::initialize,
    CamX::configure_streams,
    NULL,
    CamX::construct_default_request_settings,
    CamX::process_capture_request,
    NULL,
    CamX::dump,
    CamX::flush,
    {0},
};

定义了g_camera3DeviceOps变量：

/// Array containing camera3_device_ops_t methods
static camera3_device_ops_t g_camera3DeviceOps =
{
    CamX::initialize,
    CamX::configure_streams,
    NULL,
    CamX::construct_default_request_settings,
    CamX::process_capture_request,
    NULL,
    CamX::dump,
    CamX::flush,
    {0},
};

并在\vendor\qcom\proprietary\camx\src\core\hal\camxhaldevice.cpp的Initialize方法中通过GetCamera3DeviceOps获取，建立联系：

CamxResult HALDevice::Initialize(
    const HwModule* pHwModule,
    UINT32          cameraId)
{