话说上一篇说道
else if ( window == 0 ) {
result = mHardware->setPreviewWindow(window);//将window设置到hal层， Android代码架构真正的实现就止于此，hal层的东西就看具体厂家根据自身情况进行实现了。 }
那究竟mHardware是如何和hal联系起来的的呢？
1.在CameraClient.cpp中：
status_t CameraClient::initialize(camera_module_t *module) {
int callingPid = getCallingPid();
LOG1("CameraClient::initialize E (pid %d, id %d)", callingPid, mCameraId);
char camera_device_name[10];
status_t res;
snprintf(camera_device_name, sizeof(camera_device_name), "%d", mCameraId);
mHardware = new CameraHardwareInterface(camera_device_name);//注意到此处。
res = mHardware->initialize(&module->common);//注意此处
if (res != OK) {
ALOGE("%s: Camera %d: unable to initialize device: %s (%d)",
__FUNCTION__, mCameraId, strerror(-res), res);
mHardware.clear();
return NO_INIT;
}
mHardware->setCallbacks(notifyCallback,
dataCallback,
dataCallbackTimestamp,
(void *)mCameraId);
// Enable zoom, error, focus, and metadata messages by default
enableMsgType(CAMERA_MSG_ERROR | CAMERA_MSG_ZOOM | CAMERA_MSG_FOCUS |
CAMERA_MSG_PREVIEW_METADATA | CAMERA_MSG_FOCUS_MOVE);
//!++
#ifdef MTK_CAMERA_BSP_SUPPORT
// Enable MTK-extended messages by default
enableMsgType(MTK_CAMERA_MSG_EXT_NOTIFY | MTK_CAMERA_MSG_EXT_DATA);
#endif
//!--
LOG1("CameraClient::initialize X (pid %d, id %d)", callingPid, mCameraId);
return OK;
}mHardware = new CameraHardwareInterface(camera_device_name);//注意到此处。
mHardware 定义是 CameraHardwareInterface， 他也是Android的通用接口。 各个厂家提供的功能都要通过CameraHardwareInterface适配向CameraService提供硬件操作接口。
这篇的主题就是主要分享CameraHardwareInterface如何进行适配的。
2. 接着1中的代码片段：
res = mHardware->initialize(&module->common);//涉及到module,module即为CameraClient::initialize(camera_module_t *module)传进来的参数， 为一个结构体变量的指针。
CameraClient::initialize(camera_module_t *module)调用的地方为CameraService中connect camera的时候调用：
sp<ICamera> CameraService::connect(
const sp<ICameraClient>& cameraClient, int cameraId) {
#ifdef MTK_CAMERAPROFILE_SUPPORT
initCameraProfile();
AutoCPTLog cptlog(Event_CS_connect);
#endif
int callingPid = getCallingPid();
LOG1("CameraService::connect E (pid %d, id %d)", callingPid, cameraId);
if (!mModule) {
ALOGE("Camera HAL module not loaded");
...........................
............................
#endif
if (client->initialize(mModule) != OK) {//在这里调用CameraClient的initialize, 而传入的参数为mModule。
#ifdef MTK_CAMERAPROFILE_SUPPORT
CPTLogStr(Event_CS_newCamHwIF, CPTFlagEnd, "new CameraHardwareInterface failed");
#endif
#ifdef MTK_CAMERA_BSP_SUPPORT
Mutex mSoundLock;
sp<MediaPlayer> mSoundPlayer[NUM_SOUNDS];
int mSoundRef; // reference count (release all MediaPlayer when 0)
camera_module_t *mModule;//
为一个camera_module_t结构体变量的指针。
Camera最先被使用到的地方是在onFirstRef()函数中， 在这里主要是初始化了mModule的一些变量。 至于onFirstRef何时调用， 后续进行相关的分享， 这里大家只要记住，这个是和sp相关的， 并且在构建sp的时候就会调用。 可以参考这位的博客：http://blog.csdn.net/gzzaigcnforever/article/details/20649781
void CameraService::onFirstRef()
{
BnCameraService::onFirstRef();
if (hw_get_module(CAMERA_HARDWARE_MODULE_ID,//这个定义为"came"
(const hw_module_t **)&mModule) < 0) {//注意这个函数调用
ALOGE("Could not load camera HAL module");
mNumberOfCameras = 0;
}
else {
mNumberOfCameras = mModule->get_number_of_cameras();
if (mNumberOfCameras > MAX_CAMERAS) {
ALOGE("Number of cameras(%d) > MAX_CAMERAS(%d).",
mNumberOfCameras, MAX_CAMERAS);
mNumberOfCameras = MAX_CAMERAS;
}
for (int i = 0; i < mNumberOfCameras; i++) {
setCameraFree(i);
}
}
}
/** Base path of the hal modules */
#define HAL_LIBRARY_PATH1 "/system/lib/hw"
#define HAL_LIBRARY_PATH2 "/vendor/lib/hw"
#define HAL_LIBRARY_PATH3 "/system/lib"
int hw_get_module(const char *id, const struct hw_module_t **module)
{
return hw_get_module_by_class(id, NULL, module);
}
int hw_get_module_by_class(const char *class_id, const char *inst,
const struct hw_module_t **module)
{
int status;
int i;
const struct hw_module_t *hmi = NULL;
char prop[PATH_MAX];
char path[PATH_MAX];
char name[PATH_MAX];
if (inst)
snprintf(name, PATH_MAX, "%s.%s", class_id, inst);//class_id为camera， inst为null， 所以现在name=“camera”
else
strlcpy(name, class_id, PATH_MAX);
/*
* Here we rely on the fact that calling dlopen multiple times on
* the same .so will simply increment a refcount (and not load
* a new copy of the library).
* We also assume that dlopen() is thread-safe.
*/
/* Loop through the configuration variants looking for a module */
for (i=0 ; i<HAL_VARIANT_KEYS_COUNT+1 ; i++) {
if (i < HAL_VARIANT_KEYS_COUNT) {
if (property_get(variant_keys[i], prop, NULL) == 0) {
continue;
}
snprintf(path, sizeof(path), "%s/%s.%s.so",
HAL_LIBRARY_PATH2, name, prop);//path=/vendor/lib/hw/camera.**.so, 根据属性的配置值生成文件名。
if (access(path, R_OK) == 0) break;//判断是否有读文件权限。
snprintf(path, sizeof(path), "%s/%s.%s.so",//path=/system/lib/hw/camera.**.so
HAL_LIBRARY_PATH1, name, prop);
if (access(path, R_OK) == 0) break;
snprintf(path, sizeof(path), "%s/%s.%s.so",
HAL_LIBRARY_PATH3, name, prop);//path=/system/lib/camera.**.so
if (access(path, R_OK) == 0) break;
} else {
snprintf(path, sizeof(path), "%s/%s.default.so",
HAL_LIBRARY_PATH1, name);//path=/vendor/lib/hw/camera.default.so
if (access(path, R_OK) == 0) break;
snprintf(path, sizeof(path), "%s/%s.default.so",//path=/system/lib/camera.default.so
HAL_LIBRARY_PATH3, name);
if (access(path, R_OK) == 0) break;
}
}
status = -ENOENT;
if (i < HAL_VARIANT_KEYS_COUNT+1) {
/* load the module, if this fails, we‘re doomed, and we should not try
* to load a different variant. */
status = load(class_id, path, module);//动态加载动态库。
}
return status;
}
上面的思路就是：
遍历
#define HAL_LIBRARY_PATH1 "/system/lib/hw" #define HAL_LIBRARY_PATH2 "/vendor/lib/hw" #define HAL_LIBRARY_PATH3 "/system/lib"这几个目录下的so库，so库的名字为： a.camera.属性名.so和b.camera.default.so。 其中会优先找到a, 在没找到a后再去找到b。 在mtk平台上， 编译生成的so库就为 camera.default.so， 所以最终加载的会是camera.default.so这个库。
继续看看：load(class_id, path, module);：
static int load(const char *id,
const char *path,
const struct hw_module_t **pHmi)
{
int status;
void *handle;
struct hw_module_t *hmi;
/*
* load the symbols resolving undefined symbols before
* dlopen returns. Since RTLD_GLOBAL is not or‘d in with
* RTLD_NOW the external symbols will not be global
*/
handle = dlopen(path, RTLD_NOW);
if (handle == NULL) {
char const *err_str = dlerror();
ALOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
status = -EINVAL;
goto done;
}
/* Get the address of the struct hal_module_info. */
const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
hmi = (struct hw_module_t *)dlsym(handle, sym);//关注这两句
if (hmi == NULL) {
ALOGE("load: couldn‘t find symbol %s", sym);
status = -EINVAL;
goto done;
}
/* Check that the id matches */
if (strcmp(id, hmi->id) != 0) {
ALOGE("load: id=%s != hmi->id=%s", id, hmi->id);
status = -EINVAL;
goto done;
}
hmi->dso = handle;
/* success */
status = 0;
done:
if (status != 0) {
hmi = NULL;
if (handle != NULL) {
dlclose(handle);
handle = NULL;
}
} else {
ALOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
id, path, *pHmi, handle);
}
*pHmi = hmi;
return status;
}
关注这两句：
const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
hmi = (struct hw_module_t *)dlsym(handle, sym);//关注这两句
HAL_MODULE_INFO_SYM_AS_STR：
/** * Name of the hal_module_info */ #define HAL_MODULE_INFO_SYM HMI /** * Name of the hal_module_info as a string */ #define HAL_MODULE_INFO_SYM_AS_STR "HMI"从上面可以看出就是要获取名为“HMI”函数的指针， 而HMI又是HAL_MODULE_INFO_SYM 的宏定义， 所以最终就是要找HAL_MODULE_INFO_SYM实现的地方：
static
camera_module
instantiate_camera_module()
{
CAM_LOGD("[%s]", __FUNCTION__);
//
// (1) Prepare One-shot init.
MtkCamUtils::Property::clear();
// (2)
camera_module module = {
common: {
tag: HARDWARE_MODULE_TAG,
module_api_version: 1,
hal_api_version: 0,
id: CAMERA_HARDWARE_MODULE_ID,
name: "MTK Camera Module",
author: "MTK",
methods: CamDeviceManager::get_module_methods(),
dso: NULL,
reserved: {0},
},
get_number_of_cameras: CamDeviceManager::get_number_of_cameras,
get_camera_info: CamDeviceManager::get_camera_info,
};
return module;
}
/*******************************************************************************
* Implementation of camera_module
*******************************************************************************/
camera_module HAL_MODULE_INFO_SYM = instantiate_camera_module();
3.继续2关注到CamDeviceManager::get_module_methods()这个函数：
hw_module_methods_t*
CamDeviceManager::
get_module_methods()
{
static
hw_module_methods_t
_methods =
{
open: CamDeviceManager::open_device
};
return &_methods;
}
呵呵， 可以看到通过mModule->common->methods-->open可以引用到CamDeviceManager::open_device。
通过名字可以猜测到这个方法应该是在Camera启动的时候会去调用。
所以我们看看何时调用CamDeviceManager::open_device这个方法：
回到CameraService:CameraClient：
status_t CameraClient::initialize(camera_module_t *module) {
int callingPid = getCallingPid();
LOG1("CameraClient::initialize E (pid %d, id %d)", callingPid, mCameraId);
char camera_device_name[10];
status_t res;
snprintf(camera_device_name, sizeof(camera_device_name), "%d", mCameraId);
mHardware = new CameraHardwareInterface(camera_device_name);
res = mHardware->initialize(&module->common);//这里初始化了， 并且传入的module->common回到CameraHardwareInterface:
status_t initialize(hw_module_t *module)
{
ALOGI("Opening camera %s", mName.string());
int rc = module->methods->open(module, mName.string(),
(hw_device_t **)&mDevice);//这里进行了打开camera的操作， 这里调用到的已经是MTK hal层的方法了， 注意最后一个参数。
if (rc != OK) {
ALOGE("Could not open camera %s: %d", mName.string(), rc);
return rc;
}
initHalPreviewWindow();
return rc;
}int
CamDeviceManager::
open_device(const hw_module_t* module, const char* name, hw_device_t** device)
{
return CamDeviceManager::getInstance().openDevice(module, name, device);
}
int
CamDeviceManager::
openDevice(const hw_module_t* module, const char* name, hw_device_t** device)
{
int err = OK;
//
ICamDevice* pdev = NULL;
int32_t i4OpenId = 0;
//
Mutex::Autolock lock(mMtxOpenLock);
//
MY_LOGI("+ mi4OpenNum(%d), mi4DeviceNum(%d)", mi4OpenNum, mi4DeviceNum);
if (name != NULL)
{
i4OpenId = ::atoi(name);
//
if ( DevMetaInfo::queryNumberOfDevice() < i4OpenId )
{
err = -EINVAL;
goto lbExit;
}
//
if ( MAX_SIMUL_CAMERAS_SUPPORTED <= mi4OpenNum )
{
MY_LOGW("open number(%d) >= maximum number(%d)", mi4OpenNum, MAX_SIMUL_CAMERAS_SUPPORTED);
MY_LOGE("does not support multi-open");
err = -ENOMEM;
goto lbExit;
}
//
pdev = createIDevice(
i4OpenId,
*get_hw_device(),
module
);//注意此处， 进行camDevice的创建
//
if ( ! pdev )
{
MY_LOGE("camera device allocation fail: pdev(0)");
err = -ENOMEM;
goto lbExit;
}
*device = pdev->get_hw_device();//此处将CamDevice的指针付给传进来形参， 最终是CameraHardwareInterface中的mDevice指向了CamDevice。
//
mi4OpenNum++;
}
lbExit:
if ( OK != err )
{
if ( pdev )
{
destroyDevice(pdev);
pdev = NULL;
}
//
*device = NULL;
}
MY_LOGI("- mi4OpenNum(%d)", mi4OpenNum);
return err;
}
4.继续往下关注到
pdev = createIDevice(
i4OpenId,
*get_hw_device(),
module
);的实现：
static
ICamDevice*
createIDevice(
int32_t const i4DevOpenId,
hw_device_t const& hwdevice,
hw_module_t const*const hwmodule
)
{
g_s8ClientAppMode = queryClientAppMode();
//
MY_LOGI("+ tid:%d OpenID:%d ClientAppMode:%s", ::gettid(), i4DevOpenId, g_s8ClientAppMode.string());
//
ICamDevice* pdev = NSCamDevice::createDevice(g_s8ClientAppMode, i4DevOpenId);//pDeve 指向的就是ICamDevice的一个对象
//
if ( pdev != 0 )
{
pdev->incStrong(pdev);
//
hw_device_t* hwdev = pdev->get_hw_device();//
*hwdev = hwdevice;
hwdev->module = const_cast<hw_module_t*>(hwmodule);
//
if ( ! pdev->init() )//在这里初始化了ICamDvice
{
MY_LOGE("fail to initialize a newly-created instance");
pdev->uninit();
pdev = NULL;
}
}
//
MY_LOGI("- created instance=%p", &(*pdev));
return pdev;//返回创建的ICamDevice。
}
注意到ICamDevice对象的构造函数：
ICamDevice::
ICamDevice()
: camera_device_t()
, RefBase()
, mDevOps()
//
, mMtxLock()
//
{
MY_LOGD("ctor");
::memset(static_cast<camera_device_t*>(this), 0, sizeof(camera_device_t));
this->priv = this;
this->ops = &mDevOps;//ops指向了mDevOps
mDevOps = gCameraDevOps;//mDevOps为gCameraDevOps指向的结构体
}gCameraDevOps：
static camera_device_ops_t const gCameraDevOps = {
set_preview_window: camera_set_preview_window,
set_callbacks: camera_set_callbacks,
enable_msg_type: camera_enable_msg_type,
disable_msg_type: camera_disable_msg_type,
msg_type_enabled: camera_msg_type_enabled,
start_preview: camera_start_preview,
stop_preview: camera_stop_preview,
preview_enabled: camera_preview_enabled,
store_meta_data_in_buffers: camera_store_meta_data_in_buffers,
start_recording: camera_start_recording,
stop_recording: camera_stop_recording,
recording_enabled: camera_recording_enabled,
release_recording_frame: camera_release_recording_frame,
auto_focus: camera_auto_focus,
cancel_auto_focus: camera_cancel_auto_focus,
take_picture: camera_take_picture,
cancel_picture: camera_cancel_picture,
set_parameters: camera_set_parameters,
get_parameters: camera_get_parameters,
put_parameters: camera_put_parameters,
send_command: camera_send_command,
release: camera_release,
dump: camera_dump,
};
mDevice->ops->set_preview_window(mDevice, 0)类似的方法就可以调用到ICamDevice中对应的方法了。
5. 我们回到Camera显示相关的东西，
在CameraClient中//!++
else if ( window == 0 ) {
result = mHardware->setPreviewWindow(window);
}
进而在CameraHardwareInterface中：
/** Set the ANativeWindow to which preview frames are sent */
status_t setPreviewWindow(const sp<ANativeWindow>& buf)
{
ALOGV("%s(%s) buf %p", __FUNCTION__, mName.string(), buf.get());
if (mDevice->ops->set_preview_window) {
//!++
if ( buf == 0 ) {
ALOGD("set_preview_window(0) before mPreviewWindow = 0");
mDevice->ops->set_preview_window(mDevice, 0);//直接调用了ICamDevice的相关的方法。
mPreviewWindow = 0;
return OK;
}
//!--
mPreviewWindow = buf;
mHalPreviewWindow.user = this;
ALOGV("%s &mHalPreviewWindow %p mHalPreviewWindow.user %p", __FUNCTION__,
&mHalPreviewWindow, mHalPreviewWindow.user);
return mDevice->ops->set_preview_window(mDevice,
buf.get() ? &mHalPreviewWindow.nw : 0);
}
return INVALID_OPERATION;
}
具体思路就是：
a.CameraHardwareInterface是Android原生定义的和硬件hal层连接的适配接口。各个厂家根据需要去具体实现这些接口，并具体实现底层的相关功能。
b.为了代码通用性和模块的分离性， 对hal层模块的实现封装成动态库(so)， CameraService根据需要动态加载hal层的库。
c.CamDeviceManager是Hal层的一个入口类， 从CameraService打开关闭camera的时候都是通过它进行总的安排。
d.hal层下具体的实现都是不断的适配CameraHardwareInterface向上提供的接口的一个过程。
附上以一个打开Camera的流程图供参考：
Camera显示之Hal层的适配,布布扣,bubuko.com
原文：http://blog.csdn.net/wsb1321/article/details/21975951
