Android::开机logo

系统开机第一个程序的进程是init，它的源码位于system/core/init/init.c，其中函数load_565rle_image负责logo的显示，如果读取成功，就在/dev/graphics/fb0显示图片，如果读取失败，则将/dev/tty0设为文本模式，并打开/dev/tty0并输出android字样。之后会显示android开机动画(其实两张图片做成的效果)，logo图片由INIT_IMAGE_FILE(在init.h中)指定。

int load_565rle_image(char *fn)
{
    struct FB fb;
    struct stat s;
    unsigned short *data, *bits, *ptr;
    unsigned count, max;
    int fd;

    if (vt_set_mode(1))
        return -1;

    fd = open(fn, O_RDONLY);
    if (fd < 0) {
        ERROR("cannot open '%s'\n", fn);
        goto fail_restore_text;
    }

    if (fstat(fd, &s) < 0) {
        goto fail_close_file;
    }

    data = mmap(0, s.st_size, PROT_READ, MAP_SHARED, fd, 0);
    if (data == MAP_FAILED)
        goto fail_close_file;

    if (fb_open(&fb))
        goto fail_unmap_data;

    max = fb_width(&fb) * fb_height(&fb);
    ptr = data;
    count = s.st_size;
    bits = fb.bits;
    while (count > 3) {
        unsigned n = ptr[0];
        if (n > max)
            break;
        android_memset16(bits, ptr[1], n << 1);
        bits += n;
        max -= n;
        ptr += 2;
        count -= 4;
    }

    munmap(data, s.st_size);
    fb_update(&fb);
    fb_close(&fb);
    close(fd);
    unlink(fn);
    return 0;

fail_unmap_data:
    munmap(data, s.st_size);
fail_close_file:
    close(fd);
fail_restore_text:
    vt_set_mode(0);
    return -1;
}

如果是显示文本的话，则是和/dev/tty0打交道，而如果是图片的话，则是通过mmap将图片内容写到framebuffer的存储空间来完成。

static int console_init_action(int nargs, char **args)
{
    int fd;
    char tmp[PROP_VALUE_MAX];

    if (console[0]) {
        snprintf(tmp, sizeof(tmp), "/dev/%s", console);
        console_name = strdup(tmp);
    }

    fd = open(console_name, O_RDWR);
    if (fd >= 0)
        have_console = 1;
    close(fd);

    if( load_565rle_image(INIT_IMAGE_FILE) ) {
        fd = open("/dev/tty0", O_WRONLY);
        if (fd >= 0) {
            const char *msg;
                msg = "\n"
            "\n"
            "\n"
            "\n"
            "\n"
            "\n"
            "\n" // console is 40 cols x 30 lines
            "\n"
            "\n"
            "\n"
            "\n"
            "\n"
            "\n"
            "\n"
            " A N D R O I D ";
            write(fd, msg, strlen(msg));
            close(fd);
        }
    }
    return 0;
}

而开机的那段动画即晃动的android字样是由两幅图片组成，一张前景，一张背景，位于

代码位于frameworks/base/cmds/bootanimation/BootAnimation.cpp

if(ForcePortraitLCD == true){
        initTexture(&mAndroid[0], mAssets, "images/android-logo-mask-vertical.png");
        initTexture(&mAndroid[1], mAssets, "images/android-logo-shine-vertical.png");
    }else{
        initTexture(&mAndroid[0], mAssets, "images/android-logo-mask.png");
        initTexture(&mAndroid[1], mAssets, "images/android-logo-shine.png");
    }