前言

现在很多车载大屏都是基于Android系统，其中都会有一个开机 logo 替换程序，任你选择各大车商 logo 替换，一开机就能查看效果。

一直对这块很感兴趣，研究了发现 MTK 平台可以通过 Nvram 来存储数据，这是一种可行的方案，应用层写入index，uboot 和

kernel 读取 index 绘制对应的 logo 以达到动态替换效果。

100余款车商logo资源

开机Logo加载原理

1、u-boot logo显示原理

Little Kernel 会在 platform_early_init 阶段首先会获取 lcm params，其工作流程就是透过读id找到现在插入的LCM，

根据 LCM 的分辨率申请相应大小的 frame buffer并确定 frame buffer 起始地址，接着为 logo.bin 预留4M Ram

之后在 platform_init 阶段，直接将 logo.bin 载入到 4M Ram 中

完成载入后，在 platform_init 中 mt_disp_show_boot_logo() 会调用show_logo(0);完成第一张logo显示。

其中的index=0代表在 logo.bin 中压缩的第一张图片，logo.bin 中的图片压缩顺序可以察看文件

vendor\mediatek\proprietary\bootable\bootloader\lk\dev\logo\rules.mk

2、kernel logo 显示原理

Kernel logo 的工作方式与 U-boot logo 不同，是透过init.rc中注册的，boot_logo_updater service 完成读取raw data文件，

进行绘画的，所以在 kernel logo 只是经过了 bmp 向 raw 的转换，在目录 vendor\mediatek\proprietary\bootable\bootloader\lk\dev\logo\ 下

通过 bmp_to_raw 工具将 bmp 转换为 raw 文件，之后透过脚本文件将 boot_logo 文件搬移到

out\target\product\xxx\obj\BOOTLOADER_OBJ\build-xxx\dev\logo\wxga下，打包到 logo.bin，download 到手机中

3、logo.bin生成过程

注:图片来自

https://blog.csdn.net/u011784994/article/details/105561958

4、替换原理

U-boot logo，将不同分辨率的图片压缩至 logo.bin 中，在读取时根据不同的 NVflag 显示相应的图片即可

platform.c 中 lk_display_show_logo(void) 读取 NVflag 传递给 mt_logo.c 调用 void mt_disp_show_boot_logo(int logo_index)

Kernel logo，需要将不同分辨率的 boot_logo raw data文件生成出来并 copy 到手机中，boot_logo_updater根据不同的分辨率进行识别，

读取相应的logo文件。在 boot_logo_updater 识别部分对 NVflag 进行判断，进而调用不同的boot_logo。

charging_animation.cpp 中 void show_kernel_logo() 读取 NVflag

开机Logo制作

根据 device/mediateksample/xxx/ProjectConfig.mk 中 BOOT_LOGO= wxga 对应字段，找到

vendor\mediatek\proprietary\bootable\bootloader\lk\dev\logo\wxga 文件夹中对应的图片分辨率

在 PS 中新建同等分辨率，置入素材，最终保存为 bmp 格式即可。

知识储备

1、实现思路

2、NVram 相关介绍

NVRAM（ Non-Volatile Random Access Memory）是非易失性随机访问存储器，指断电后仍能保持数据的一种 RAM。

MTK 源码中提供了相关的工具类读写，写入 NVRam 中的数据恢复出厂也不会丢失。

有关 NVRAM 可查看 MTK NVRAM

3、不同区域读取 NVRam 数据

应用层读写 Nvram 方法网上有很多，而且很容易验证。uboot 和 kernel 读取比较稀少，找了很久参考如下的文章

不同区域读取NVRAM数据

经过N次不停修改尝试后，最终苍天不负，终于搞定。

有了以上对于 NVram 相关认知，那我们就来撸代码吧。

动态替换实现

1、java 层读写 NVram

java 层主要通过 INvram 接口来读写，对应的需要导入静态库，

LOCAL_STATIC_JAVA_LIBRARIES += vendor.mediatek.hardware.nvram-V1.0-java-static

显然在AS 中是编译不过的，所以只能放到源码环境通过配置 Android.mk 的方式编译。

测试用 Android.mk 文件

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
#引入静态库读写nvram
LOCAL_STATIC_JAVA_LIBRARIES += vendor.mediatek.hardware.nvram-V1.0-java-static
LOCAL_MODULE_TAGS :=  optional
LOCAL_SRC_FILES := $(call all-subdir-java-files)
LOCAL_PACKAGE_NAME := NvramDemo
#编译后的apk路径在data目录下
LOCAL_MODULE_PATH := $(TARGET_OUT_DATA_APPS)
include $(BUILD_PACKAGE)

也有可能你的源码中 nvram 版本不是 V1.0,可以通过 find -name “*.java” | xargs grep “/vendor/nvdata/” 命令搜索

那个 app 也操作了 nvram，复制对应mk中的版本号就行。

测试用 NVActivity 代码如下

package com.android.qrdc;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.Arrays;

import vendor.mediatek.hardware.nvram.V1_0.INvram;
import com.android.internal.util.HexDump;

public class NVActivity extends Activity {

    private static final String TAG = "NVActivity";
    private TextView tv_result;
    private EditText cmdEt;

    private static void log(String msg) {
        Log.e("NVActivity", msg);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.nv_layout);

        tv_result = findViewById(R.id.tv_result);
        cmdEt = findViewById(R.id.cmdEt);
    }

    public void readNv(View v) {
        log("readNv click");

        tv_result.setText("read result"+ readData());
    }

    public void writeNv(View v) {
        String cmd = cmdEt.getText().toString();
        log("writeNv click -----" + cmd);
         writeData(Integer.parseInt(cmd));
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }

    public static final String PRODUCT_INFO_FILENAME = "/vendor/nvdata/APCFG/APRDEB/PRODUCT_INFO";
    private static  void writeData(int n) {
        byte[] write_buff = new byte[]{0, 0, 0, 0};
        byte[] by = getBytes(n);
        for (int i = 0; i < 4; i++) {
            write_buff[i] = by[i];
        }
        try {
            INvram agent = INvram.getService();
            if (agent != null) {
                ArrayList<Byte> dataArray = new ArrayList<>(4);
                for (byte b : write_buff) {
                    dataArray.add(new Byte(b));
                }
                int ret_1 = agent.writeFileByNamevec(PRODUCT_INFO_FILENAME, 537, dataArray);
                if (ret_1>0){
                    log("write success"+ ret_1);
                }else {
                    log("write failed"+ ret_1);
                }
            } else {
                Log.e(TAG, "writeData: agent null");
            }
        } catch (Exception e) {
            Log.e(TAG, "writeData exception:" + e.getLocalizedMessage());
            e.printStackTrace();
        }
    }

    private static  byte[] getBytes(int data) {
        byte[] bytes = new byte[4];
        bytes[0] = (byte) (data & 0xff);
        bytes[1] = (byte) ((data & 0xff00) >> 8);
        bytes[2] = (byte) ((data & 0xff0000) >> 16);
        bytes[3] = (byte) ((data & 0xff000000) >> 24);
        return bytes;
    }

    public static  int readData() {
        int targets = 0;
        try {
            String buff = null;
            INvram agent = INvram.getService();
            Log.i(TAG, "readData from PRODUCT_INFO_FILENAME");
            if (agent != null) {
                buff = agent.readFileByName(PRODUCT_INFO_FILENAME, 537);
            }
            byte[] buffArr = HexDump.hexStringToByteArray(buff.substring(0, buff.length() - 1));
            targets = (buffArr[0] & 0xff) | ((buffArr[1] << 8) & 0xff00) | ((buffArr[2] << 24) >>> 8) | (buffArr[3] << 24);
            Log.i(TAG, "readData: buffArr=" + Arrays.toString(buffArr) + ", targets == " + targets);
        } catch (Exception e) {
            Log.e(TAG, "readData exception:" + e.getLocalizedMessage());
            e.printStackTrace();
        }
        return targets;
    }
}

测试 demo 运行图，demo apk 下载链接

简单验证后能正常读写 nvram，那我们就需要对 demo 进行大改造，思路如下

1、预置开机logo缩略图，通过 GridView 加载展示

2、点击 GridView 中图片弹框提示是否需要替换开机logo

3、确定替换将logo缩略图对应index值写入 nvram 中

4、重启可查看效果

核心读写 nvram 方法已提供，其它代码太多就不贴了。

修改代码清单

vendor/mediatek/proprietary/bootable/bootloader/lk/dev/logo/rules.mk  
vendor/mediatek/proprietary/bootable/bootloader/lk/dev/logo/update  
vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6735/include/platform/mt_logo.h  
vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6735/mt_logo.c  
vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6735/platform.c  
vendor/mediatek/proprietary/external/libshowlogo/Android.mk  
vendor/mediatek/proprietary/external/libshowlogo/charging_animation.cpp  
vendor/mediatek/proprietary/external/libshowlogo/charging_animation.h

2、native 层读取 NVram

kernel logo 绘制方法位于 charging_animation.cpp 中 void show_kernel_logo()

头文件中增加 int nvram_read_index(void) 获取 index 方法

vendor\mediatek\proprietary\external\libshowlogo\charging_animation.h

+++ b/alps/vendor/mediatek/proprietary/external/libshowlogo/charging_animation.h
@@ -110,7 +110,7 @@ void anim_surface_deinit(void);
 
 // show logo function
 void anim_show_logo(int index);
-
+int  nvram_read_index(void);
 
 #ifdef __cplusplus
 }

vendor\mediatek\proprietary\external\libshowlogo\charging_animation.cpp

//cczheng add read kernel logo index from nvram
#define MAX_RETRY_COUNT 100
int nvram_read_index(void){
    int logo_index = kernel_logo_position;
    int read_nvram_ready_retry = 0;
    F_ID fid;
    int rec_size = 0;
    int rec_num = 0;
    int nvinfo_lid = AP_CFG_REEB_PRODUCT_INFO_LID;
    char *nvdata_result;
    bool isread = false;
    char nvram_init_val[128] = {0};
    SLOGE("Entry get_barcode_from_nvram");

    while (read_nvram_ready_retry < MAX_RETRY_COUNT) {
        read_nvram_ready_retry++;
        property_get("service.nvram_init", nvram_init_val, NULL);
        if (strcmp(nvram_init_val, "Ready") == 0) {
            break;
        } else {
            usleep(500 * 1000);
        }
    }

    if (read_nvram_ready_retry >= MAX_RETRY_COUNT) {
        SLOGE("Get nvram restore ready failed!");
        return logo_index;
    }
    nvdata_result = (char *) malloc(1024);
    if (nvdata_result == NULL) {
        return logo_index;
    }
    fid = NVM_GetFileDesc(nvinfo_lid, &rec_size, &rec_num, isread);
    if (fid.iFileDesc < 0) {
        SLOGE("fid.iFileDesc < 0");
        free(nvdata_result);
        return logo_index;
    }

    if (rec_size != read(fid.iFileDesc, nvdata_result, rec_size)) {
        free(nvdata_result);
        return logo_index;
    }

   
    free(nvdata_result);
    if (!NVM_CloseFileDesc(fid)) {
        return logo_index;
    }

    SLOGE("nvramstr hex buff[0]%x, buff[1]%x, buff[2]%x, buff[3]%x \n",
    nvdata_result[0],nvdata_result[1],nvdata_result[2],nvdata_result[3]);

    SLOGE("The size of nvdata_result:%d\n", sizeof(nvdata_result));

    SLOGE("nvramstr dex buff[0]=%d, buff[1]=%d, buff[2]=%d, buff[3]=%d \n",
    nvdata_result[0],nvdata_result[1],nvdata_result[2],nvdata_result[3]);

    logo_index = nvdata_result[0];
    return logo_index;
}


void show_kernel_logo()
{
    if (MTK_LOG_ENABLE == 1) {
        SLOGD("[libshowlogo: %s %d]show kernel logo, index = 38 \n",__FUNCTION__,__LINE__);
    }
	if (error_flag == 0) {
#if defined(MTK_CARRIEREXPRESS_PACK)
		anim_show_logo(get_logo_index(false));
        SLOGE("[show_kernel_logo: get_logo_index %d", get_logo_index(false));
#else
        //cczheng add read index from nvram data
        kernel_logo_position = nvram_read_index();
		anim_show_logo(kernel_logo_position);
        SLOGE("[show_kernel_logo: %d %d]show kernel logo, \n",__LINE__, kernel_logo_position);
#endif
    }
}

同时还需要在 Android.mk 中导入所需 nvram 库

vendor\mediatek\proprietary\external\libshowlogo\Android.mk

+++ b/alps/vendor/mediatek/proprietary/external/libshowlogo/Android.mk
@@ -50,8 +50,8 @@ endif
 endif
 endif
 
-LOCAL_SHARED_LIBRARIES := libcutils libutils libc libstdc++ libz libdl liblog libgui libui libsysenv_system libbase
-
+LOCAL_SHARED_LIBRARIES := libcutils libutils libc libstdc++ libz libdl liblog libgui libui libsysenv_system libbase libnvram_mtk libcustom_nvram_mtk

LOCAL_STATIC_LIBRARIES += libfs_mgr
 
 LOCAL_C_INCLUDES += $(MTK_PATH_CUSTOM)/lk/include/target
@@ -62,6 +62,14 @@ LOCAL_C_INCLUDES += $(TOP)/frameworks/native/libs/nativewindow/include
 LOCAL_C_INCLUDES += system/core/fs_mgr/include
 LOCAL_C_INCLUDES += $(TOP)/vendor/mediatek/proprietary/external/libsysenv
 
+LOCAL_C_INCLUDES += vendor/mediatek/proprietary/external/nvram/libnvram \
+                                       vendor/mediatek/proprietary/custom/ \
+                                       $(MTK_PATH_SOURCE)/external/nvram/libfile_op \
+                                       $(MTK_PATH_CUSTOM)/cgen/inc \
+                                       $(MTK_PATH_CUSTOM)/cgen/cfgfileinc \
+                                       vendor/mediatek/proprietary/custom/common/cgen/cfgfileinc \
+                                       vendor/mediatek/proprietary/custom/common/cgen/inc
+
 LOCAL_MODULE := libshowlogo
 #LOCAL_PROPRIETARY_MODULE := true
 #LOCAL_MODULE_OWNER := mtk

调试小技巧

通过 jni log 打印读取的数据，查找其中index值，其中需要进制转换，分别打印了 16 进制和 10 进制，通过 log 查找正确的结果

烧写时只勾选 lk、boot、logo 替换即可，加快烧写验证速度。

3、uboot 区域读取 NVram

uboot 阶段相比 kernel 要困难太多，一开始没法看日志，不知道读取的值是否正确，后来灵机一动，加上去除之前 oem 解锁后屏幕

显示警告文字也是在 uboot 阶段显示，那这里应该也行，果不其然通过 video_printf() 打印日志调试就很方便，mtk 真是太牛逼了！

uboot logo 绘制方法位于 mt_logo.cpp 中 void mt_disp_show_boot_logo(void)

修改头文件，传递 index 值，显示动态替换logo

vendor\mediatek\proprietary\bootable\bootloader\lk\platform\mt6735\include\platform\mt_logo.h

+++ b/alps/vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6735/include/platform/mt_logo.h
@@ -58,7 +58,8 @@ const LOGO_CUST_IF *LOGO_GetCustomIF(void);
 void mt_disp_enter_charging_state(void);
 void mt_disp_show_battery_full(void);
 void mt_disp_show_battery_capacity(UINT32 capacity);
-void mt_disp_show_boot_logo(void);
+// void mt_disp_show_boot_logo(void);
+void mt_disp_show_boot_logo(int logo_index);
 void mt_disp_show_low_battery(void);

修改实现方法，参数传递 logo_index

vendor\mediatek\proprietary\bootable\bootloader\lk\platform\mt6735\mt_logo.c

+++ b/alps/vendor/mediatek/proprietary/bootable/bootloader/lk/platform/mt6735/mt_logo.c
@@ -266,9 +266,12 @@ void mt_logo_get_custom_if(void)
  * Show first boot logo when phone boot up
  *
  */
-void mt_disp_show_boot_logo(void)
-{
-       int logo_index = 0;
+//cczheng change param void to int
+// void mt_disp_show_boot_logo(void)
+void mt_disp_show_boot_logo(int logo_index)
+{      
+       //cczheng annotaion
+       //int logo_index = 0;
        dprintf(INFO, "[lk logo: %s %d]\n",__FUNCTION__,__LINE__);
        mt_logo_get_custom_if();
 		
		if (logo_cust_if->show_boot_logo) {
			logo_cust_if->show_boot_logo();
		} else {
			///show_logo(0);
			init_fb_screen();
			fill_animation_logo(logo_index, mt_get_fb_addr(), mt_get_tempfb_addr(), logo_addr, phical_screen);
			mt_disp_update(0, 0, CFG_DISPLAY_WIDTH, CFG_DISPLAY_HEIGHT);
		}
	
		return;
}

platform 中读取 nvram 值传递给 mt_logo

vendor\mediatek\proprietary\bootable\bootloader\lk\platform\mt6735\platform.c

//cczheng add uboot read nvram logo index
int get_bootlogo_flag(void) {
    long len, length;
    u64 start_address;
    part_t *part;
    part_dev_t *dev;
    char *part_name = "proinfo";
    dev = mt_part_get_device();
    if (!dev) {
        video_printf(" => !dev is true...\n");
        return 0;
    }

    part = mt_part_get_partition(part_name);
    if (!part) {
        video_printf(" => mboot_get_boot_logo_flag--- part = NULL\n");
        dprintf(INFO, "mboot_get_boot_logo_flag--- part = NULL");
        return 0;
    }

    dprintf(INFO, "mboot_get_boot_logo_flag--- get_partition 1\n");
    length = 1024;

    start_address = (u64)part->start_sect * dev->blkdev->blksz;
    video_printf(" => start_address=%llu\n", start_address);//524288
			
    unsigned char *addr;
    addr = (unsigned char *) malloc(length * sizeof(unsigned char));
    
    int index = partition_get_index(part_name);
    if (index == -1) {
        video_printf(" => partition_get_index == -1\n");
        dprintf(INFO, "mboot_get_boot_logo_flag--- partition_get_index =%d\n", index);
        return 0;
    }
    unsigned int part_id = partition_get_region(index);
	len = dev->read(dev, start_address, (uchar *) addr, length, part_id);

    if (len < 0) {
        video_printf(" => dev->read len < 0\n");
        dprintf(INFO, "mboot_get_boot_logo_flag--- dev->read len=%ld\n", len);
        return 0;
    }

    video_printf(" => part_dev->read addr=%s\n", addr);//&
	video_printf("The size of nvdata_result:%d\n", sizeof(addr));//4
	video_printf("nvramstr dex buff[0]=%d, buff[1]=%d, buff[2]=%d, buff[3]=%d \n",
    addr[0],addr[1],addr[2],addr[3]);//26

    int result = addr[0];//boot logo flag
    dprintf(INFO,"mboot_get_boot_logo_flag addr = %d\n",result);
    video_printf(" => result=%d\n", result);

    return result;
}

static void lk_display_show_logo(void)
{
#ifdef LK_PROFILING
	unsigned int time_show_logo = get_timer(0);
#endif // LK_PROFILING

#ifndef MACH_FPGA_NO_DISPLAY
	// mt_disp_show_boot_logo();

	//cczheng add read logo index and pass to mt_logo 
	int logo_index = get_bootlogo_flag();
	video_printf(" => mt_disp_show_boot_logo==%d\n", logo_index);
	mt_disp_show_boot_logo(logo_index);
#endif // MACH_FPGA_NO_DISPLAY

	logo_lk_t = ((unsigned int)get_timer(boot_time));

#ifdef LK_PROFILING
	dprintf(CRITICAL, "[PROFILE] show logo takes %d ms\n", (int)get_timer(time_show_logo));
#endif // LK_PROFILING
}

4、预置logo资源打包到rom中

经过上面修改，读写 nvram 都已正常，最后预置 logo bmp 图片打包即可，还需修改如下两个地方

在 (BOOT_LOGO)_kernel.raw 后面增加要打包进的资源图片名称，可配置 N 个，index值在 kernel 后依次累加。