android双屏显示的一些修改与尝试

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文章出处： http://www.cnblogs.com/xl19862005

作者：Xandy

用的是android2.3的代码

这些天来一直在看android display相关的代码和资料并作了一些尝试，现在将这些天来的工作记录如下，有错误的地方希望广大同行指正，谢谢！

经过阅读代码和查到的相关一些资料，对android双屏的支持总体思路如下图所示：

由于目前跟踪代码只跟到了surfaceflinger这一层，下面先从surfaceflinger说起：

在frameworks\base\services\surfaceflinger\surfaceflinger.cpp这个文件中有如下代码片断：

status_t SurfaceFlinger::readyToRun()
{
    LOGI("SurfaceFlinger's main thread ready to run. Initializing graphics H/W...\n");

    // we only support one display currently
    int dpy = 0;

    {
        // initialize the main display
        GraphicPlane& plane(graphicPlane(dpy));
        DisplayHardware* const hw = new DisplayHardware(this, dpy);
        
        DisplayHardware* const hw1 = new DisplayHardware(this, 1); //这个是我加入测试HAL层用的，下面将介绍到
        
        plane.setDisplayHardware(hw);
    }

    // create the shared control-block
    mServerHeap = new MemoryHeapBase(4096,MemoryHeapBase::READ_ONLY, "SurfaceFlinger read-only heap");
    LOGE_IF(mServerHeap==0, "can't create shared memory dealer");
    
    mServerCblk = static_cast<surface_flinger_cblk_t*>(mServerHeap->getBase());
    LOGE_IF(mServerCblk==0, "can't get to shared control block's address");
    
    new(mServerCblk) surface_flinger_cblk_t;

    // initialize primary screen
    // (other display should be initialized in the same manner, but
    // asynchronously, as they could come and go. None of this is supported
    // yet).
    const GraphicPlane& plane(graphicPlane(dpy));
    const DisplayHardware& hw = plane.displayHardware();
    const uint32_t w = hw.getWidth();
    const uint32_t h = hw.getHeight();
    const uint32_t f = hw.getFormat();
    hw.makeCurrent();

    // initialize the shared control block
    mServerCblk->connected |= 1<<dpy;
    display_cblk_t* dcblk = mServerCblk->displays + dpy;
    memset(dcblk, 0, sizeof(display_cblk_t));
    dcblk->w            = plane.getWidth();
    dcblk->h            = plane.getHeight();
    dcblk->format       = f;
    dcblk->orientation  = ISurfaceComposer::eOrientationDefault;
    dcblk->xdpi         = hw.getDpiX();
    dcblk->ydpi         = hw.getDpiY();
    dcblk->fps          = hw.getRefreshRate();
    dcblk->density      = hw.getDensity();

    // Initialize OpenGL|ES
    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
    glPixelStorei(GL_PACK_ALIGNMENT, 4); 
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnable(GL_SCISSOR_TEST);
    glShadeModel(GL_FLAT);
    glDisable(GL_DITHER);
    glDisable(GL_CULL_FACE);

    const uint16_t g0 = pack565(0x0F,0x1F,0x0F);
    const uint16_t g1 = pack565(0x17,0x2f,0x17);
    const uint16_t textureData[4] = { g0, g1, g1, g0 };
    glGenTextures(1, &mWormholeTexName);
    glBindTexture(GL_TEXTURE_2D, mWormholeTexName);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameterx(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 2, 2, 0,GL_RGB, GL_UNSIGNED_SHORT_5_6_5, textureData);

    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrthof(0, w, h, 0, 0, 1);

   LayerDim::initDimmer(this, w, h);

    mReadyToRunBarrier.open();

    /*
     *  We're now ready to accept clients...
     */

    // start boot animation
    property_set("ctl.start", "bootanim");
    
    return NO_ERROR;
}

　　重点看上面用黄色标出的那两行，其中DisplayHardware* const hw1 = new DisplayHardware(this, 1);是我加入用来测试HAL层的buffer分配用的，DisplayHardware这个是在frameworks\base\services\surfaceflinger\DisplayHardware\DisplayHardware.cpp这个文件中定义的，如以下代码片断：

/*
 * Initialize the display to the specified values.
 *
 */
DisplayHardware::DisplayHardware(const sp<SurfaceFlinger>& flinger,uint32_t dpy)
    : DisplayHardwareBase(flinger, dpy),mFlags(0)
{
    init(dpy);
}

　　而在同文件中有如下代码片断：

void DisplayHardware::init(uint32_t dpy)
{
    mNativeWindow = new FramebufferNativeWindow(dpy);
    
    framebuffer_device_t const * fbDev = mNativeWindow->getDevice();
    mDpiX = mNativeWindow->xdpi;
    mDpiY = mNativeWindow->ydpi;
    mRefreshRate = fbDev->fps;

    mOverlayEngine = NULL;
    hw_module_t const* module;
    if (hw_get_module(OVERLAY_HARDWARE_MODULE_ID, &module) == 0) 
    {
        overlay_control_open(module, &mOverlayEngine);
    }

    EGLint w, h, dummy;
    EGLint numConfigs=0;
    EGLSurface surface;
    EGLContext context;

    // initialize EGL
    EGLint attribs[] = 
    {
            EGL_SURFACE_TYPE,  
            EGL_WINDOW_BIT,
            EGL_NONE,        
            0,
            EGL_NONE
    };

    // debug: disable h/w rendering
    char property[PROPERTY_VALUE_MAX];
    if (property_get("debug.sf.hw", property, NULL) > 0) 
    {
        if (atoi(property) == 0) 
        {
            LOGW("H/W composition disabled");
            attribs[2] = EGL_CONFIG_CAVEAT;
            attribs[3] = EGL_SLOW_CONFIG;
        }
    }

    // TODO: all the extensions below should be queried through
    // eglGetProcAddress().

    // set to EGL wrapper to load SW OpenGLES only
     if (property_get("debug.sf.enable_hgl", property, "1") > 0)
     {
        if (atoi(property) == 0) 
        {
            eglSetImplementationAndroid(EGL_TRUE);
        }
    }

/*下面这些都是和egl相关的，目前正在研究中，由于代码量太大，一起不好发上来，这里简单介绍一下，frameworks\base\opengl\libagl目录下是agl相关的一些代码，这些代码会生成libGLES_android.so 这个动态库，这点可以从此目录下的Android.mk文件里看出：

LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/egl
LOCAL_MODULE:= libGLES_android

    在frameworks\base\opengl\libs目录下是egl相关的一些代码，这些代码主要把agl这个库作了个封装，并向外提供相关接口*/
    EGLDisplay display = eglGetDisplay((NativeDisplayType)dpy);//(EGL_DEFAULT_DISPLAY);
    LOGI("******DisplayHardware.cpp display:%d******\n",(int)display);
    eglInitialize(display, NULL, NULL);
    eglGetConfigs(display, NULL, 0, &numConfigs);

    EGLConfig config;
    status_t err = EGLUtils::selectConfigForNativeWindow(display, attribs, mNativeWindow.get(), &config);
    LOGE_IF(err, "couldn't find an EGLConfig matching the screen format");
    
    EGLint r,g,b,a;
    eglGetConfigAttrib(display, config, EGL_RED_SIZE,   &r);
    eglGetConfigAttrib(display, config, EGL_GREEN_SIZE, &g);
    eglGetConfigAttrib(display, config, EGL_BLUE_SIZE,  &b);
    eglGetConfigAttrib(display, config, EGL_ALPHA_SIZE, &a);

    if (mNativeWindow->isUpdateOnDemand()) 
        mFlags |= PARTIAL_UPDATES;
    
    if (eglGetConfigAttrib(display, config, EGL_CONFIG_CAVEAT, &dummy) == EGL_TRUE) 
    {
        if (dummy == EGL_SLOW_CONFIG)
            mFlags |= SLOW_CONFIG;
    }

    /*
     * Create our main surface
     */

    surface = eglCreateWindowSurface(display, config, mNativeWindow.get(), NULL);
    eglQuerySurface(display, surface, EGL_WIDTH,  &mWidth);
    eglQuerySurface(display, surface, EGL_HEIGHT, &mHeight);

    if (mFlags & PARTIAL_UPDATES) 
    {
        // if we have partial updates, we definitely don't need to
        // preserve the backbuffer, which may be costly.
        eglSurfaceAttrib(display, surface,EGL_SWAP_BEHAVIOR, EGL_BUFFER_DESTROYED);
    }

    if (eglQuerySurface(display, surface, EGL_SWAP_BEHAVIOR, &dummy) == EGL_TRUE) 
    {
        if (dummy == EGL_BUFFER_PRESERVED) 
        {
            mFlags |= BUFFER_PRESERVED;
        }
    }
    
    /* Read density from build-specific ro.sf.lcd_density property
     * except if it is overridden by qemu.sf.lcd_density.
     */
    if (property_get("qemu.sf.lcd_density", property, NULL) <= 0)
    {
        if (property_get("ro.sf.lcd_density", property, NULL) <= 0)
        {
            LOGW("ro.sf.lcd_density not defined, using 160 dpi by default.");
            strcpy(property, "160");
        }
    }
    else 
    {
        /* for the emulator case, reset the dpi values too */
        mDpiX = mDpiY = atoi(property);
    }
    mDensity = atoi(property) * (1.0f/160.0f);


    /*
     * Create our OpenGL ES context
     */
    

    EGLint contextAttributes[] = 
    {
#ifdef EGL_IMG_context_priority
#ifdef HAS_CONTEXT_PRIORITY
#warning "using EGL_IMG_context_priority"
        EGL_CONTEXT_PRIORITY_LEVEL_IMG, EGL_CONTEXT_PRIORITY_HIGH_IMG,
#endif
#endif
        EGL_NONE, EGL_NONE
    };
    context = eglCreateContext(display, config, NULL, contextAttributes);

    mDisplay = display;
    mConfig  = config;
    mSurface = surface;
    mContext = context;
    mFormat  = fbDev->format;
    mPageFlipCount = 0;

    /*
     * Gather OpenGL ES extensions
     */

    eglMakeCurrent(display, surface, surface, context);

    GLExtensions& extensions(GLExtensions::getInstance());
    extensions.initWithGLStrings(glGetString(GL_VENDOR),
                                                 glGetString(GL_RENDERER),
                                                 glGetString(GL_VERSION),
                                                 glGetString(GL_EXTENSIONS),
                                                 eglQueryString(display, EGL_VENDOR),
                                                 eglQueryString(display, EGL_VERSION),
                                                 eglQueryString(display, EGL_EXTENSIONS));

    glGetIntegerv(GL_MAX_TEXTURE_SIZE, &mMaxTextureSize);
    glGetIntegerv(GL_MAX_VIEWPORT_DIMS, &mMaxViewportDims);


#ifdef EGL_ANDROID_swap_rectangle
    if (extensions.hasExtension("EGL_ANDROID_swap_rectangle")) 
    {
        if (eglSetSwapRectangleANDROID(display, surface,0, 0, mWidth, mHeight) == EGL_TRUE) 
        {
            // This could fail if this extension is not supported by this
            // specific surface (of config)
            mFlags |= SWAP_RECTANGLE;
        }
    }
    // when we have the choice between PARTIAL_UPDATES and SWAP_RECTANGLE
    // choose PARTIAL_UPDATES, which should be more efficient
#ifdef FSL_EPDC_FB
#else
    if (mFlags & PARTIAL_UPDATES)
        mFlags &= ~SWAP_RECTANGLE;
#endif
#endif

    LOGI("EGL informations:");
    LOGI("# of configs : %d", numConfigs);
    LOGI("vendor    : %s", extensions.getEglVendor());
    LOGI("version   : %s", extensions.getEglVersion());
    LOGI("extensions: %s", extensions.getEglExtension());
    LOGI("Client API: %s", eglQueryString(display, EGL_CLIENT_APIS)?:"Not Supported");
    LOGI("EGLSurface: %d-%d-%d-%d, config=%p", r, g, b, a, config);

    LOGI("OpenGL informations:");
    LOGI("vendor    : %s", extensions.getVendor());
    LOGI("renderer  : %s", extensions.getRenderer());
    LOGI("version   : %s", extensions.getVersion());
    LOGI("extensions: %s", extensions.getExtension());
    LOGI("GL_MAX_TEXTURE_SIZE = %d", mMaxTextureSize);
    LOGI("GL_MAX_VIEWPORT_DIMS = %d", mMaxViewportDims);
    LOGI("flags = %08x", mFlags);

    // Unbind the context from this thread
    eglMakeCurrent(display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
}

　　上面代码黄色标出的将会new一个framebufferNativeWindow，其实就是通过HAL层的Gralloc这个库映射到kernel层中的framebuffer

　　在frameworks\base\libs\ui\FramebufferNativeWindow.cpp这个文件中有如下代码片断：

FramebufferNativeWindow::FramebufferNativeWindow(uint32_t dpy)
    : BASE(), fbDev(0), grDev(0), mUpdateOnDemand(false)
{
    hw_module_t const* module;
    char GRALLOC_MODE[10];
    char GRALLOC_FB[10];
    char GRALLOC_GPU[10];

    if(dpy == DISPLAY0)
    {
        strcpy(GRALLOC_MODE,GRALLOC_HARDWARE_MODULE_ID0);
        strcpy(GRALLOC_FB,GRALLOC_HARDWARE_FB0);
        strcpy(GRALLOC_GPU,GRALLOC_HARDWARE_GPU0);
    }
    else if(dpy == DISPLAY1)
    {
        strcpy(GRALLOC_MODE,GRALLOC_HARDWARE_MODULE_ID1);
        strcpy(GRALLOC_FB,GRALLOC_HARDWARE_FB1);
        strcpy(GRALLOC_GPU,GRALLOC_HARDWARE_GPU1);
    }
    else
    {
        strcpy(GRALLOC_MODE,GRALLOC_HARDWARE_MODULE_ID0);
        strcpy(GRALLOC_FB,GRALLOC_HARDWARE_FB0);
        strcpy(GRALLOC_GPU,GRALLOC_HARDWARE_GPU0);
    }

/*这个函数的原型是没有传入参数的，为了增加对second display的支持自行加入的，上面这些代码也是后来加入的，为的是根据传入的dpy（display 0/1）打开相应的Gralloc和GPU的库文件*/
    
    if (hw_get_module(GRALLOC_MODE, &module) == 0) 
    {
        int stride;
        int err;
        int i;
        err = framebuffer_open(module,GRALLOC_FB, &fbDev);
        LOGE_IF(err, "couldn't open framebuffer HAL (%s)", strerror(-err));
        
        err = gralloc_open(module,GRALLOC_GPU, &grDev);
        LOGE_IF(err, "couldn't open gralloc HAL (%s)", strerror(-err));

        // bail out if we can't initialize the modules
        if (!fbDev || !grDev)
            return;
        
        mUpdateOnDemand = (fbDev->setUpdateRect != 0);
        
        // initialize the buffer FIFO
 mNumBuffers = fbDev->reserved[0];
        if (mNumBuffers != 3 && mNumBuffers != 2) 
        {
            LOGE("The framebuffer number got from HAL is not supported(%d)", mNumBuffers);
            return;
        }
        mNumFreeBuffers = mNumBuffers;

        mBufferHead = mNumBuffers-1;

        for (i = 0; i < mNumBuffers; i++) buffers[i] = new NativeBuffer(fbDev->width, fbDev->height, fbDev->format, GRALLOC_USAGE_HW_FB); for (i = 0; i < mNumBuffers; i++) { err = grDev->alloc(grDev,fbDev->width, fbDev->height, fbDev->format,GRALLOC_USAGE_HW_FB, &buffers[i]->handle, &buffers[i]->stride); LOGE_IF(err, "fb buffer %d allocation failed w=%d, h=%d, err=%s",i, fbDev->width, fbDev->height, strerror(-err));
 }

        const_cast<uint32_t&>(ANativeWindow::flags) = fbDev->flags; 
        const_cast<float&>(ANativeWindow::xdpi) = fbDev->xdpi;
        const_cast<float&>(ANativeWindow::ydpi) = fbDev->ydpi;
        const_cast<int&>(ANativeWindow::minSwapInterval) = fbDev->minSwapInterval;
        const_cast<int&>(ANativeWindow::maxSwapInterval) = fbDev->maxSwapInterval;
    } 
    else 
    {
        LOGE("Couldn't get gralloc module");
    }

    ANativeWindow::setSwapInterval = setSwapInterval;
    ANativeWindow::dequeueBuffer = dequeueBuffer;
    ANativeWindow::lockBuffer = lockBuffer;
    ANativeWindow::queueBuffer = queueBuffer;
    ANativeWindow::query = query;
    ANativeWindow::perform = perform;
}

　　重点在上面用黄色标出的这几行代码，hw_get_module会根据传入的dpy选择打开gralloc0还是gralloc1，framebuffer_open会根据传入的dpy选择打开fb0还是fb1，gralloc_open会根据传入的dpy选择打开gpu0还是gpu1；接下来的几行代码都是和buffer相关，mNumBuffers在这里等于3，先new NativeBuffer得到相应的buffers[i](i=0/1/2)，grDev->alloc将会为这些buffers分配内存。

　　在hardware\libhardware\include\hardware\Gralloc.h文件中有如下定义，为了加入second display我这里作了一些修改

/**
 * The id of this module
 */
#define GRALLOC_HARDWARE_MODULE_ID0   "gralloc0"
#define GRALLOC_HARDWARE_MODULE_ID1  "gralloc1"

/**
 * Name of the graphics device to open
 */

#define GRALLOC_HARDWARE_FB0 "fb0"
#define GRALLOC_HARDWARE_FB1 "fb1"
#define GRALLOC_HARDWARE_GPU0 "gpu0"
#define GRALLOC_HARDWARE_GPU1 "gpu1"

.
.
.
.

/** convenience API for opening and closing a supported device 下面这些封装都是在得到了module这个结构体之后得到相应的函数入口*/

static inline int gralloc_open(const struct hw_module_t* module, const char * name,struct alloc_device_t** device) 
{
    return module->methods->open(module, name, (struct hw_device_t**)device);
}

static inline int gralloc_close(struct alloc_device_t* device) 
{
    return device->common.close(&device->common);
}


static inline int framebuffer_open(const struct hw_module_t* module,const char * name, struct framebuffer_device_t** device) 
{
    return module->methods->open(module,name, (struct hw_device_t**)device);
}

static inline int framebuffer_close(struct framebuffer_device_t* device) 
{
    return device->common.close(&device->common);
}

　　上面这些代码就是通过打开不同的gralloc模块，得到不同的函数入口地址，这里我对gralloc分别新建了两个，一个映射到fb0，一个映射到fb1，如下文件列表：

　　

其中libgralloc_sec_display是我后来加入的，先看libgralloc里面的内容：

在gralloc.cpp这个文件里有如下代码片断：

/*这里的open就是打开gralloc这个模块之后与在gralloc.h中module->methods->open相对应了*/
static struct hw_module_methods_t gralloc_module_methods = 
{
        open: gralloc_device_open
};

struct private_module_t HAL_MODULE_INFO_SYM = {
    base: 
    {
        common: 
        {
            tag: HARDWARE_MODULE_TAG,
            version_major: 1,
            version_minor: 0,
            id: GRALLOC_HARDWARE_MODULE_ID0,
            name: "Graphics Memory Allocator Module",
            author: "The Android Open Source Project",
            methods: &gralloc_module_methods
        },
        registerBuffer: gralloc_register_buffer,
        unregisterBuffer: gralloc_unregister_buffer,
        lock: gralloc_lock,
        unlock: gralloc_unlock,
    },
    framebuffer: 0,
    flags: 0,
    numBuffers: 0,
    bufferMask: 0,
    lock: PTHREAD_MUTEX_INITIALIZER,
    currentBuffer: 0,
    pmem_master: -1,
    pmem_master_base: 0,
    master_phys: 0
};

　　open的实现代码如下：

int gralloc_device_open(const hw_module_t* module, const char* name,hw_device_t** device)
{
    int status = -EINVAL;

    //name = GRALLOC_HARDWARE_FB0 or GRALLOC_HARDWARE_GPU0
    GRALLLOGI0("*********gralloc_devide_open : name = %s********\n",name);
    if (!strcmp(name, GRALLOC_HARDWARE_GPU0)) 
    {
        gralloc_context_t *dev;
        dev = (gralloc_context_t*)malloc(sizeof(*dev));

        /* initialize our state here */
        memset(dev, 0, sizeof(*dev));

        /* initialize the procs */
        dev->device.common.tag = HARDWARE_DEVICE_TAG;
        dev->device.common.version = 0;
        dev->device.common.module = const_cast<hw_module_t*>(module);
        dev->device.common.close = gralloc_close;

        dev->device.alloc   = gralloc_alloc;
        dev->device.free    = gralloc_free;

        *device = &dev->device.common;
        status = 0;
    } 
    else 
    {
        status = fb_device_open(module, name, device);/* 这里是调用了同目录下framebuffer.cpp文件中的函数*/
    }
    return status;
}

　　同样在gralloc_sec_display这个里面也会有如上一样的内容，这里不再列出，其实以上说的这些都是在为framebuffer在内存中的分配作准备包括GPU在内存中的空间。

在framebuffer.cpp文件中有如下代码片断：

int fb_device_open(hw_module_t const* module, const char* name,hw_device_t** device)
{
    int status = -EINVAL;
    char value[PROPERTY_VALUE_MAX];

    if (!strcmp(name, GRALLOC_HARDWARE_FB0)) 
    {
        alloc_device_t* gralloc_device;
        framebuffer_device_t *fbdev;

        nr_framebuffers = NUM_BUFFERS;
        property_get("ro.product.device", value, "");
        if (0 == strcmp(value, "imx50_rdp")) {
            nr_framebuffers = 2;
            no_ipu = 1;
        }

        status = gralloc_open(module,GRALLOC_HARDWARE_GPU0, &gralloc_device);
        if (status < 0)
            return status;

        /* initialize our state here */
        fb_context_t *dev = (fb_context_t*)malloc(sizeof(*dev));
        memset(dev, 0, sizeof(*dev));

        /* initialize the procs */
        dev->device.common.tag = HARDWARE_DEVICE_TAG;
        dev->device.common.version = 0;
        dev->device.common.module = const_cast<hw_module_t*>(module);
        dev->device.common.close = fb_close;
        dev->device.setSwapInterval = fb_setSwapInterval;
        dev->device.post = fb_post;
        #ifndef FSL_EPDC_FB
        dev->device.setUpdateRect = 0;
        #else
        dev->device.setUpdateRect = fb_setUpdateRect;
        #endif
        dev->device.compositionComplete = fb_compositionComplete;
        #ifdef TVOUT_DISPLAY_SUPPORT
        dev->device.setSecRotation = fb_setSecRotation;
        #endif

        private_module_t* m = (private_module_t*)module;
        status = mapFrameBuffer(m);
        if (status >= 0) 
        {
            int stride = m->finfo.line_length / (m->info.bits_per_pixel >> 3);
            const_cast<uint32_t&>(dev->device.flags) = 0xfb0;
            const_cast<uint32_t&>(dev->device.width) = m->info.xres;
            const_cast<uint32_t&>(dev->device.height) = m->info.yres;
            const_cast<int&>(dev->device.stride) = stride;
            if(m->info.bits_per_pixel != 32) 
            {
                const_cast<int&>(dev->device.format) = HAL_PIXEL_FORMAT_RGB_565;
            }
            else
            {
                const_cast<int&>(dev->device.format) = HAL_PIXEL_FORMAT_BGRA_8888;
            }
            const_cast<float&>(dev->device.xdpi) = m->xdpi;
            const_cast<float&>(dev->device.ydpi) = m->ydpi;
            const_cast<float&>(dev->device.fps) = m->fps;
            const_cast<int&>(dev->device.minSwapInterval) = 1;
            const_cast<int&>(dev->device.maxSwapInterval) = 1;
            *device = &dev->device.common;
            fbdev = (framebuffer_device_t*) *device;
            fbdev->reserved[0] = nr_framebuffers;
        }

    /* initialize the IPU lib IPC */
        if (!no_ipu)
            mxc_ipu_lib_ipc_init();
    }
    return status;
}

　　这里重点在上面黄色标出的两处，fb_post和刷屏相关，只要FB0里面的数据有变化，就会行动这里面的代码，mapFrameBuffer会把内核空间的fb0映射到用户空间，这样上层就能使用fb0了 。

　　gralloc1与gralloc0的不同之处主要在于对fb的映射，gralloc0是把fb0映射到了用户空间并与LCD0绑定，而gralloc1则是把fb1映射到了用户空间并与LCD1绑定，在framebuffer_sec.cpp有如下代码片断：

/********************************************************
*name:mapTVFrameBufferLocked
*param:module
*author:Xandy
*说明:此函数经过改装过，把fb1映射给了LCD1
********************************************************/

int mapTVFrameBufferLocked(struct TV_fb_module_t* module)
{
    // already initialized...
    if (module->TVframebuffer) 
    {
        return 0;
    }

    int TV_fd = -1;
    struct mxcfb_color_key key; 

    set_graphics_fb_mode(1, 1);
    TV_fd = open("/dev/graphics/fb1", O_RDWR, 0);

    if (TV_fd < 0)
        return -errno;

    struct fb_fix_screeninfo finfo;
    if (ioctl(TV_fd, FBIOGET_FSCREENINFO, &finfo) == -1)
        return -errno;

    struct fb_var_screeninfo info;
    if (ioctl(TV_fd, FBIOGET_VSCREENINFO, &info) == -1)
        return -errno;

    info.reserved[0] = 0;
    info.reserved[1] = 0;
    info.reserved[2] = 0;
    info.xoffset = 0;
    info.yoffset = 0;
    info.activate = FB_ACTIVATE_NOW;
                

　　而framebuffer.cpp相同的地方则如下：

int mapFrameBufferLocked(struct private_module_t* module)
{
    // already initialized...
    if (module->framebuffer) 
    {
        return 0;
    }
        
    char const * const device_template[] = {
            "/dev/graphics/fb%u",
            "/dev/fb%u",
            0 };

    int fd = -1;
    int i=0;
    char name[64];

    char value[PROPERTY_VALUE_MAX];
    property_get("ro.UI_TVOUT_DISPLAY", value, "");
    if (strcmp(value, "1") != 0) 
    {
        set_graphics_fb_mode(0, 0);
        while ((fd==-1) && device_template[i]) {
            snprintf(name, 64, device_template[i], 0);
            fd = open(name, O_RDWR, 0);
            i++;
        }
    }
    else
    {
        set_graphics_fb_mode(1, 0);
        while ((fd==-1) && device_template[i]) { snprintf(name, 64, device_template[i], 1); fd = open(name, O_RDWR, 0); i++;
 }
    }

    if (fd < 0)
        return -errno;

    struct fb_fix_screeninfo finfo;
    if (ioctl(fd, FBIOGET_FSCREENINFO, &finfo) == -1)
        return -errno;

    struct fb_var_screeninfo info;
    if (ioctl(fd, FBIOGET_VSCREENINFO, &info) == -1)
        return -errno;

　　下面看看串口打印出来的信息：

/*系统起来后，开启ServiceManager，这是因为SurfaceFlinger是一个service*/

I/sysproc ( 2098): Entered system_init()
I/sysproc ( 2098): ServiceManager: 0x11d9f8
I/SurfaceFlinger( 2098): SurfaceFlinger is starting  /*SurfaceFlinger启动，这个service将会一直运行*/
I/SurfaceFlinger( 2098): SurfaceFlinger's main thread ready to run. Initializing graphics H/W...
I/imx5x.gralloc0( 2098): *********gralloc_devide_open : name = fb0********  /*打开gralloc0之后，得到得到相应的函数入口并为fb0与gpu0分配内存*/
I/imx5x.gralloc0( 2098): *********gralloc_devide_open : name = gpu0********

/*fb0初始化之后的一些信息*/

I/imx5x.gralloc0( 2098): 16bpp setting of Framebuffer catched!
I/imx5x.gralloc0( 2098): using (fd=24)
I/imx5x.gralloc0( 2098): id           = DISP3 BG
I/imx5x.gralloc0( 2098): xres         = 800 px
I/imx5x.gralloc0( 2098): yres         = 480 px
I/imx5x.gralloc0( 2098): xres_virtual = 800 px
I/imx5x.gralloc0( 2098): yres_virtual = 1536 px
I/imx5x.gralloc0( 2098): bpp          = 16
I/imx5x.gralloc0( 2098): r            = 11:5
I/imx5x.gralloc0( 2098): g            =  5:6
I/imx5x.gralloc0( 2098): b            =  0:5
I/imx5x.gralloc0( 2098): width        = 127 mm (160.000000 dpi)
I/imx5x.gralloc0( 2098): height       = 76 mm (160.421051 dpi)
I/imx5x.gralloc0( 2098): refresh rate = 62.02 Hz
I/imx5x.gralloc0( 2098): *********gralloc_devide_open : name = gpu0********
I/imx5x.gralloc0( 2098): ******Gralloc.cpp numBuffers:3******
I/imx5x.gralloc0( 2098): ******Gralloc.cpp numBuffers:3******
I/imx5x.gralloc0( 2098): ******Gralloc.cpp numBuffers:3******
I/FslOverlay( 2098): hardware/mx5x/liboverlay/overlay.cpp: overlay_device_open
I/FslOverlay( 2098): overlay_device_open control pid 2098,tid 2106
I/FslOverlay( 2098): hardware/mx5x/liboverlay/overlay.cpp: overlay_init_fbdev
I/FslOverlay( 2098): /dev/graphics/fb0 fb_var: bits_per_pixel 16,xres 800,yres 480,xres_virtual 800,yres_virtual 1536
I/FslOverlay( 2098): hardware/mx5x/liboverlay/overlay.cpp: create_control_shared_data
I/FslOverlay( 2098): ***************create_control_shared_data mmap in*********************
I/FslOverlay( 2098): ***************create_control_shared_data mmap out:0x2ea3e000****************
I/FslOverlay( 2098): hardware/mx5x/liboverlay/overlay_thread.h: onFirstRef
I/FslOverlay( 2098): Overlay HAL control device Created successfully

/*load egl库*/
I/libEGL  ( 2098): ******eglGetDisplay in egl : 0******
I/FslOverlay( 2098): Overlay thread running pid 2098 tid 2108
D/libEGL  ( 2098): loaded /system/lib/egl/libGLES_android.so
I/libagl  ( 2098): ******eglGetDisplay in libagl : 0******
I/libEGL  ( 2098): ******Egl.cpp IMPL_SOFTWARE dpy=1
D/libEGL  ( 2098): loaded /system/lib/egl/libEGL_imx51.so
D/libEGL  ( 2098): loaded /system/lib/egl/libGLESv1_CM_imx51.so
D/libEGL  ( 2098): loaded /system/lib/egl/libGLESv2_imx51.so
I/libEGL  ( 2098): ******Egl.cpp IMPL_HARDWARE dpy=1
I/SurfaceFlinger( 2098): ******DisplayHardware.cpp display:1******
I/libEGL  ( 2098): ******egl.cpp eglInitialize******
I/libEGL  ( 2098): ******egl.cpp IMX5X,dp->disp[0].dpy=0x2******
I/libEGL  ( 2098): initialized 0 dpy=0x2, ver=1.4, cnx=0x6be08b54
I/libEGL  ( 2098): ******egl.cpp IMX5X,dp->disp[1].dpy=0x1******
I/libagl  ( 2098): ******libagl.cpp eglInitialize******
I/libEGL  ( 2098): initialized 1 dpy=0x1, ver=1.2, cnx=0x6be08c0c
I/libEGL  ( 2098): ******egl egl.cpp eglCreateWindowSurface******
W/SurfaceFlinger( 2098): ro.sf.lcd_de*****************mxcfb_set_par*****************

/*ipu相关，这些都是在kernel和HAL进行的*/
mxc_ipu mxc_ipu: Channel already disabled 7

mxc_ipu mxc_ipu: Channel already uninitialized 7

TVE: fb mode change event: xres=1280, yres=1024

nsity not defined, using 160 dpi**********************fb mmap in:0x2f8c1000*******************

 by default.
I/SurfaceFlinger( *****************************ipuv3 fb mmap in 0x2f8c1000*************************

2098): EGL informations:
I/SurfaceFlinger( 2098): # of configs : 35
I/SurfaceFlinger( 2098): vendor    : Advanced Micro Devices, Inc
I/SurfaceFlinger( 2098): version   : 1.4 Internal version 1.4.1
I/SurfaceFlinger( 2098): extensions: eglCreatePbufferFromClientBuffer EGL_KHR_image EGL_KHR_image_base EGL_KHR_image_pixmap EGL_ANDROID_image_native_buffer EGL_AMD_create_image
I/SurfaceFlinger( 2098): Client API: NULL
I/SurfaceFlinger( 2098): EGLSurface: 5-6-5-0, config=0x6
I/SurfaceFlinger( 2098): OpenGL informations:
I/SurfaceFlinger( 2098): vendor    : Advanced Micro Devices, Inc.
I/SurfaceFlinger( 2098): renderer  : AMD Z430
I/SurfaceFlinger( 2098): version   : OpenGL ES-CM 1.1
I/SurfaceFlinger( 2098): extensions: GL_AMD_compressed_3DC_texture GL_AMD_compressed_ATC_texture GL_AMD_performance_monitor GL_ATI_compressed_texture_atitc GL_ATI_texture_compression_atitc GL_OES_blend_equation_separate GL_OES_blend_func_separate GL_OES_blend_subtract GL_OES_compressed_ETC1_RGB8_texture GL_OES_compressed_paletted_texture GL_OES_draw_texture GL_OES_extended_matrix_palette GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_framebuffer_object GL_OES_matrix_palette GL_OES_point_size_array GL_OES_point_sprite GL_OES_read_format GL_OES_stencil_wrap GL_OES_texture_cube_map GL_OES_texture_env_crossbar GL_OES_texture_mirrored_repeat 
I/SurfaceFlinger( 2098): GL_MAX_TEXTURE_SIZE = 2048
I/SurfaceFlinger( 2098): GL_MAX_VIEWPORT_DIMS = 2048
I/SurfaceFlinger( 2098): flags = 00000000

/*上面是在surfaceflinger.cpp上DisplayHardware* const hw = new DisplayHardware(this, dpy);这个所创建的，下面的则是我自己加入的DisplayHardware* const hw1 = new DisplayHardware(this, 1);这句所创建的，由于目前做的是车载双屏系统，后台一个电视，这里把xres与yres设置成了1280x1024px*/

I/imx5x.gralloc1( 2098): *********gralloc_devide_open : name = fb1********
I/imx5x.gralloc1( 2098): *********gralloc_devide_open : name = gpu1********
I/imx5x.gralloc1( 2098): using (TV_fd=34)
I/imx5x.gralloc1( 2098): id           = DISP3 BG - DI1
I/imx5x.gralloc1( 2098): xres         = 1280 px
I/imx5x.gralloc1( 2098): yres         = 1024 px
I/imx5x.gralloc1( 2098): xres_virtual = 1280 px
I/imx5x.gralloc1( 2098): yres_virtual = 3072 px
I/imx5x.gralloc1( 2098): bpp          = 16
I/imx5x.gralloc1( 2098): r            = 11:5
I/imx5x.gralloc1( 2098): g            =  5:6
I/imx5x.gralloc1( 2098): b            =  0:5
I/imx5x.gralloc1( 2098): width        = 203 mm (160.157639 dpi)
I/imx5x.gralloc1( 2098): height       = 163 mm (159.568100 dpi)
I/imx5x.gralloc1( 2098): refresh rate = 60.56 Hz
I/imx5x.gralloc1( 2098): *********gralloc_devide_open : name = gpu1********
I/imx5x.gralloc1( 2098): ******Gralloc.cpp numBuffers:3******
I/imx5x.gralloc1( 2098): ******Gralloc.cpp numBuffers:3******
I/imx5x.gralloc1( 2098): ******Gralloc.cpp numBuffers:3******
I/FslOverlay( 2098): hardware/mx5x/liboverlay/overlay.cpp: overlay_device_open
I/FslOverlay( 2098): overlay_device_open control pid 2098,tid 2106
I/FslOverlay( 2098): hardware/mx5x/liboverlay/overlay.cpp: overlay_init_fbdev
I/FslOverlay( 209pmem: request for physical address of pmem region from process 2104.

8): /dev/graphics/fb0 fb_var: bits_per_pixel 16,xres 800,yres 480,xres_virtual 800,yres_virtual 1536
I/FslOverlay( 2098): hardware/mx5x/liboverlay/overlay.cpp: create_control_shared_data
I/FslOverlay( 2098): ***************create_control_shared_data mmap in*********************
I/FslOverlay( 2098): ***************create_control_shared_data mmap out:0x2ea48000****************
I/FslOverlay( 2098): hardware/mx5x/liboverlay/overlay_thread.h: onFirstRef
I/FslOverlay( 2098): Overlay HAL control device Created successfully
I/libEGL  ( 2098): ******eglGetDisplay in egl : 1******
I/SurfaceFlinger( 2098): ******DisplayHardware.cpp display:2******
I/libEGL  ( 2098): ******egl.cpp eglInitialize******
I/libEGL  ( 2098): ******egl.cpp IMX5X,dp->disp[0].dpy=0x3******
I/libEGL  ( 2098): initialized 0 dpy=0x3, ver=1.4, cnx=0x6be08b54
I/libEGL  ( 2098): ******egl.cpp IMX5X,dp->disp[1].dpy=0x0******

/*这里还有一些问题需要解决，主要是egl相关的一些东西，目前正在研究中！*/
I/libagl  ( 2098): libagl egl.cpp:display is valid!!******
W/libEGL  ( 2098): 1: eglInitialize(0x0) failed (EGL_BAD_DISPLAY)
I/libEGL  ( 2098): ******egl egl.cpp eglCreateWindowSurface******
E/imx5x.gralloc1( 2098): FBIOPAN_DISPLAY failed
W/SurfaceFlinger( 2098): ro.sf.lcd_density not defined, using 160 dpi by default.
E/imx5x.gralloc1( 2098): FBIOPAN_DISPLAY failed
I/FslOverlay( 2098): Overlay thread running pid 2098 tid 2111
I/SurfaceFlinger( 2098): EGL informations:
I/SurfaceFlinger( 2098): # of configs : 27
I/SurfaceFlinger( 2098): vendor    : Advanced Micro Devices, Inc
I/SurfaceFlinger( 2098): version   : 1.4 Internal version 1.4.1
I/SurfaceFlinger( 2098): extensions: eglCreatePbufferFromClientBuffer EGL_KHR_image EGL_KHR_image_base EGL_KHR_image_pixmap EGL_ANDROID_image_native_buffer EGL_AMD_create_image
I/SurfaceFlinger( 2098): Client API: NULL
I/SurfaceFlinger( 2098): EGLSurface: 5-6-5-0, config=0x6
I/SurfaceFlinger( 2098): OpenGL informations:
I/SurfaceFlinger( 2098): vendor    : Advanced Micro Devices, Inc.
I/SurfaceFlinger( 2098): renderer  : AMD Z430
I/SurfaceFlinger( 2098): version   : OpenGL ES-CM 1.1
I/SurfaceFlinger( 2098): extensions: GL_AMD_compressed_3DC_texture GL_AMD_compressed_ATC_texture GL_AMD_performance_monitor GL_ATI_compressed_texture_atitc GL_ATI_texture_compression_atitc GL_OES_blend_equation_separate GL_OES_blend_func_separate GL_OES_blend_subtract GL_OES_compressed_ETC1_RGB8_texture GL_OES_compressed_paletted_texture GL_OES_draw_texture GL_OES_extended_matrix_palette GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_framebuffer_object GL_OES_matrix_palette GL_OES_point_size_array GL_OES_point_sprite GL_OES_read_format GL_OES_stencil_wrap GL_OES_texture_cube_map GL_OES_texture_env_crossbar GL_OES_texture_mirrored_repeat 
I/SurfaceFlinger( 2098): GL_MAX_TEXTURE_SIZE = 2048
I/SurfaceFlinger( 2098): GL_MAX_VIEWPORT_DIMS = 2048
I/SurfaceFlinger( 2098): flags = 00000000