识别和匹配idc配置文件

void EventHub::loadConfigurationLocked(Device* device) {
    device->configurationFile = getInputDeviceConfigurationFilePathByDeviceIdentifier(
            device->identifier, INPUT_DEVICE_CONFIGURATION_FILE_TYPE_CONFIGURATION);//get IDC文件
    if (device->configurationFile.isEmpty()) {
        ALOGD("No input device configuration file found for device '%s'.",
                device->identifier.name.string());
    } else {
        status_t status = PropertyMap::load(device->configurationFile,
                &device->configuration);//找到配置文件，解析出来保存到device->configuration中
        if (status) {//解析出错，
            ALOGE("Error loading input device configuration file for device '%s'.  "
                    "Using default configuration.",
                    device->identifier.name.string());
        }
    }
}

String8 getInputDeviceConfigurationFilePathByDeviceIdentifier(
        const InputDeviceIdentifier& deviceIdentifier,
        InputDeviceConfigurationFileType type) {
    if (deviceIdentifier.vendor !=0 && deviceIdentifier.product != 0) {
        if (deviceIdentifier.version != 0) {
            // Try vendor product version.
            String8 versionPath(getInputDeviceConfigurationFilePathByName(
                    String8::format("Vendor_%04x_Product_%04x_Version_%04x",
                            deviceIdentifier.vendor, deviceIdentifier.product,
                            deviceIdentifier.version),
                    type));
            if (!versionPath.isEmpty()) {
                return versionPath;
            }
        }

        // Try vendor product.
        String8 productPath(getInputDeviceConfigurationFilePathByName(
                String8::format("Vendor_%04x_Product_%04x",
                        deviceIdentifier.vendor, deviceIdentifier.product),
                type));
        if (!productPath.isEmpty()) {
            return productPath;
        }
    }

    // Try device name.
    return getInputDeviceConfigurationFilePathByName(deviceIdentifier.name, type);
}

String8 getInputDeviceConfigurationFilePathByName(
        const String8& name, InputDeviceConfigurationFileType type) {
    // Search system repository.
    String8 path;
    path.setTo(getenv("ANDROID_ROOT"));
    path.append("/usr/");
    appendInputDeviceConfigurationFileRelativePath(path, name, type);
#if DEBUG_PROBE
    ALOGD("Probing for system provided input device configuration file: path='%s'", path.string());
#endif
    if (!access(path.string(), R_OK)) {
#if DEBUG_PROBE
        ALOGD("Found");
#endif
        return path;
    }

    // Search user repository.
    // TODO Should only look here if not in safe mode.
    path.setTo(getenv("ANDROID_DATA"));
    path.append("/system/devices/");
    appendInputDeviceConfigurationFileRelativePath(path, name, type);
#if DEBUG_PROBE
    ALOGD("Probing for system user input device configuration file: path='%s'", path.string());
#endif
    if (!access(path.string(), R_OK)) {
#if DEBUG_PROBE
        ALOGD("Found");
#endif
        return path;
    }

    // Not found.
#if DEBUG_PROBE
    ALOGD("Probe failed to find input device configuration file: name='%s', type=%d",
            name.string(), type);
#endif
    return String8();
}

这里出现了两个环境变量：
echo $ANDROID_ROOT /system
echo $ANDROID_DATA /data
识别和匹配配置文件的顺序为：
/system/usr/idc/Vendor_XXXX_Product_XXXX_Version_XXXX.idc
/data/system/devices/idc/Vendor_XXXX_Product_XXXX_Version_XXXX.idc
/system/usr/idc/Vendor_XXXX_Product_XXXX.idc
/data/system/devices/idc/Vendor_XXXX_Product_XXXX.idc
/system/usr/idc/DEVICE_NAME.idc
/data/system/devices/idc/DEVICE_NAME.idc
需要注意的是文件名中的数字需要小写。例如
input_dev­>id.vendor = 0xDEAD;
input_dev­>id.product = 0xBEEF;
input_dev­>id.version = 0x0102;
对应的配置文件名应该是Vendor_dead_Product_beef_Version_0102.idc或者Vendor_dead_Product_beef.idc。
获取配置文件名的时候，如果发现文件名中含有不是ascii(<=0x7f)的字符；或者是ascii，但不是数字，不是希腊字母，也不是“-”和“_”，比如说空格、tab等，就要转成字符'_'。所以dumpsys input看到的ConfigurationFile: /system/usr/idc/Vendor_dead_Product_beef.idc，也许和我们定义的有点不一样，那就是定义了非法字符，被转了。只要找到ConfigurationFile就可以了。