gralloc 学习

1. 首先给自己做个list， 方便查找

camera 用到ANativewindow src code

         /frameworks/av/services/camera/libcameraservice/CameraHardwareInterface.h
         /system/core/include/system/window.h
        /frameworks/native/libs/gui/SurfaceTextureClient.cpp

2 . ANativeWindow API:

在这一过程中使用的API

        a 、cancelBuffer

        Hook used to cancel a buffer that has been dequeued. No synchronization is performed between dequeue() and cancel(), so either external synchronization is needed, or these functions must be called from the same thread.

        b、 queuebuffer  ---

        Hook called by EGL when modifications to the render buffer are done. This unlocks and post the buffer

The window holds a reference to the buffer between dequeueBuffer and either queueBuffer or cancelBuffer, so clients only need their own reference if they might use the buffer after queueing or canceling it.

         c、dequeuebuffer

         Hook called by EGL to acquire a buffer. This call may block if no buffers are available.

          d、lock_buffer -- do nothing

    static int __lock_buffer(struct preview_stream_ops* w,
                      buffer_handle_t* /*buffer*/)
    {
        ANativeWindow *a = anw(w);
        (void)a;
        return 0;
    }

3. GraphicBufferMapper

         GraphicBufferMapper& mapper(GraphicBufferMapper::get());

         mapper.lock(*phandle, CAMHAL_GRALLOC_USAGE, rect, &img);

The (*lock)() method is called before a buffer is accessed for the specified usage.

This call may block, for instance if the h/w needsto finish rendering or if CPU caches need to be synchronized.  

          The caller promises to modify only pixels in the area specified by (l,t,w,h).

        mapper.unlock((buffer_handle_t) *phandle);

             The (*unlock)() method must be called after all changes to the buffer are completed.

those function been defined in 

           hardware/libhardware/include/hardware/gralloc.h

      gralloc.cpp

 88         registerBuffer: gralloc_register_buffer,
  89         unregisterBuffer: gralloc_unregister_buffer,
  90         lock: gralloc_lock,                                                                                                                                      
  91         unlock: gralloc_unlock,   ->gc_gralloc_lock
  92         perform: gralloc_perform,

      lock:   1. Lock android native buffer and get Vaddress

       unlock: ion_flush(hnd);