Camera显示之Hal层的适配(一)

barry798 2014-04-28

展开全文

本篇接着上一篇：

Camera显示之Framework层设置显示窗口

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：

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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;

}

从代码片段：

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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：

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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。

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CameraClient::initialize(camera_module_t *module)调用的地方为CameraService中connect camera的时候调用：

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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

所以这里我们就关注下mModule这成员， mModule的定义：

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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

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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

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#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);：

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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：

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const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
hmi = (struct hw_module_t *)dlsym(handle, sym);//关注这两句

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HAL_MODULE_INFO_SYM_AS_STR：

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/**
* 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：

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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();

上面这个代码片段就是mtk实现的，结合上边，可以得到*pHmi指向了module这个结构体。也即是说最后将*pHmi指向这里的module。进一步回到上面，就是CameraService中的mModule指向了这里的module。所以说后面的引用大概是CameraService中通过mModule->common->methods这种方式去或则mModule->get_number_of_cameras实现到MTK的hal层的调用。这样就将Android原生CameraService通过CameraHardwareInterface连接到MTK实现的Hal层，通过CamDeviceManager来承上启下的作用。

3.继续2关注到CamDeviceManager::get_module_methods()这个函数：

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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：

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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:

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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;
}

关注到CamDeviceManager::open_device

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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

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pdev = createIDevice(
i4OpenId,
*get_hw_device(),
module
);

的实现：

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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。
}