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File CameraHardwareInterface.h

Status_t startPreview ()

{

ALOGV ("s (s)", _ _ FUNCTION__, mName.string ())

If (mDevice- > ops- > start_preview)

Return mDevice- > ops- > start_preview (mDevice)

Return INVALID_OPERATION

}

First

Private: camera_device_t * mDevice

Initialization assignment is performed in the method initialize

Status_t initialize (CameraModule * module) {

. . .

If (module- > getModuleApiVersion () > = CAMERA_MODULE_API_VERSION_2_3 & &

Info.device_version > CAMERA_DEVICE_API_VERSION_1_0) {

/ / Open higher version camera device as HAL1.0 device.

Rc = module- > openLegacy (mName.string ()

CAMERA_DEVICE_API_VERSION_1_0

(hw_device_t *) & mDevice)

} else {

Rc = module- > oCameraHardwareInterface.hpen (mName.string (), (hw_device_t * *) & mDevice)

/ / notice that the secondary pointer here, mDevice, should finally be intended to point to a structure.

}

. . .

}

Then come to the CameraModule.cpp file.

Int CameraModule::open (const char* id, struct hw_device_t** device) {

Int res

ATRACE_BEGIN ("camera_module- > open")

Res = filterOpenErrorCode (mModule- > common.methods- > open (& mModule- > common, id, device))

ATRACE_END ()

Return res

}

Here the mModule variable definition

Camera_module_t * mModule

As for the following common, it is actually an attribute of the camera_module_t structure

Typedef struct camera_module {

. . .

Hw_module_t common; / / here is not a pointer

. . .

}

Continue typedef struct hw_module_t {

. . .

Struct hw_module_methods_t* methods

. . .

}

Typedef struct hw_module_methods_t {

/ * * Open a specific device * /

Int (* open) (const struct hw_module_t* module, const char* id)

Struct hw_device_t** device)

} hw_module_methods_t

I can understand now.

MModule- > common.methods- > open (& mModule- > common, id, device)

Continue to device, which is the hw_device_t object instance

Typedef struct camera_device {

Hw_device_t common

Camera_device_ops_t * ops

Void * priv

} camera_device_t

Open is a pointer function that points to the camera_device_open method of QCamera2Factory

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