http://blog.csdn.net/joard_yang/article/details/7834772
CameraService.cpp (frameworks\base\services\camera\libcameraservice)
中调用hw_get_module
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void CameraService::onFirstRef()
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{
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BnCameraService::onFirstRef();
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"color:#ff0000;">if (hw_get_module(CAMERA_HARDWARE_MODULE_ID,
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(const hw_module_t **)&mModule) < 0) {
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LOGE("Could not load camera HAL module");
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mNumberOfCameras = 0;
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}
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else {
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mNumberOfCameras = mModule->get_number_of_cameras();
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if (mNumberOfCameras > MAX_CAMERAS) {
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LOGE("Number of cameras(%d) > MAX_CAMERAS(%d).",
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mNumberOfCameras, MAX_CAMERAS);
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mNumberOfCameras = MAX_CAMERAS;
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}
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for (int i = 0; i < mNumberOfCameras; i++) {
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setCameraFree(i);
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}
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}
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}
看一下hw_get_module是怎么回事
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int hw_get_module(const char *id, const struct hw_module_t **module)
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{
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return "color:#ff0000;">hw_get_module_by_class(id, NULL, module);
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}
他只是一个封装实际调用了hw_get_module_by_class@Hardware.c (hardware\libhardware)
好在不长,看看吧
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int hw_get_module_by_class(const char *class_id, const char *inst,
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const struct hw_module_t **module)
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{
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int status;
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int i;
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const struct hw_module_t *hmi = NULL;
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"color:#ff0000;"> char prop[PATH_MAX];
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char path[PATH_MAX];
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char name[PATH_MAX];
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if (inst)
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snprintf(name, PATH_MAX, "%s.%s", class_id, inst);
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else
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strlcpy(name, class_id, PATH_MAX);
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for (i=0 ; i
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if (i < HAL_VARIANT_KEYS_COUNT) {
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if (property_get(variant_keys[i], prop, NULL) == 0)
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"color:#ff0000;">
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"ro.hardware[qcom]"
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"ro.product.board"[7x27],
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"ro.board.platform"[msm7627a],
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"ro.arch",
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"ro.hw_platform"[QRD_SKU3-1100]
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这几个属性文件中获得硬件的信息
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有些硬件信息的字符串会出现在编译后生成的.so名字中
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{
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continue;
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}
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snprintf(path, sizeof(path), "%s/%s.%s.so",
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HAL_LIBRARY_PATH2, name, prop);
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if (access(path, R_OK) == 0) break;
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snprintf(path, sizeof(path), "%s/%s.%s.so",
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HAL_LIBRARY_PATH1, name, prop);"color:#ff0000;">
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这样一个路径,这个库里有QualcommCamera.cpp,这是
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camera模块HAL代码开始的地方
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if (access(path, R_OK) == 0) break;
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} else {
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snprintf(path, sizeof(path), "%s/%s.default.so",
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HAL_LIBRARY_PATH1, name);
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if (access(path, R_OK) == 0) break;
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}
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}
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status = -ENOENT;
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if (i < HAL_VARIANT_KEYS_COUNT+1) {
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-
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status = load(class_id, path, module);"color:#ff0000;">
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到path(/system/lib/hw/camera.msm7627a.so)这个路径下找到一个id(camera)匹配的module
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}
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return status;
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}
再来看看load这个函数@hardware.c (hardware\libhardware)
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static int load(const char *id,
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const char *path,
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const struct hw_module_t **pHmi)
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{
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int status;
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void *handle;
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struct hw_module_t *hmi;
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handle = dlopen(path, RTLD_NOW);
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if (handle == NULL) {
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char const *err_str = dlerror();
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LOGE("load: module=%s\n%s", path, err_str?err_str:"unknown");
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status = -EINVAL;
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goto done;
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}
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"color:#ff0000;">
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const char *sym = HAL_MODULE_INFO_SYM_AS_STR;
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hmi = (struct hw_module_t *)dlsym(handle, sym);
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if (hmi == NULL) {
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LOGE("load: couldn't find symbol %s", sym);
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status = -EINVAL;
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goto done;
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}
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if (strcmp(id, hmi->id) != 0) {
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LOGE("load: id=%s != hmi->id=%s", id, hmi->id);
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status = -EINVAL;
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goto done;
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}
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hmi->dso = handle;
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status = 0;
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done:
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if (status != 0) {
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hmi = NULL;
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if (handle != NULL) {
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dlclose(handle);
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handle = NULL;
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}
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} else {
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LOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",
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id, path, *pHmi, handle);
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}
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*pHmi = hmi;
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return status;
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}
在打开的.so(camera.msm7627a.so)中查找HMI符号的地址,并保存在hmi中。至此,.so中的hw_module_t已经被成功获取,从而可以根
据它获取别的相关接口。
1)HAL通过hw_get_module函数获取hw_module_t
2)HAL通过hw_module_t->methods->open获取hw_device_t指针,并在此open函数中初始化hw_device_t的包装结构中的
函数及hw_device_t中的close函数,如gralloc_device_open。
3)三个重要的数据结构:
a) struct hw_device_t: 表示硬件设备,存储了各种硬件设备的公共属性和方法
b)struct hw_module_t: 可用hw_get_module进行加载的module
c)struct hw_module_methods_t: 用于定义操作设备的方法,其中只定义了一个打开设备的方法open.
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