获取色彩深度问题

[Mack_liu]

本人最近调试飞凌开发板的显示问题，有问题请教一下：
平台：iMX6DL
内核：3.0.35
在fbmem.c文件中fb_prepare_logo函数中，函数开始获取色深

int fb_prepare_logo(struct fb_info *info, int rotate)
{
	//获取当前图片的色深
        int depth = fb_get_color_depth(&info->var, &info->fix);
        unsigned int yres;
//初始化fb_logo
        memset(&fb_logo, 0, sizeof(struct logo_data));
//-------?--start
        if (info->flags & FBINFO_MISC_TILEBLITTING ||
            info->flags & FBINFO_MODULE)
                return 0;

        if (info->fix.visual == FB_VISUAL_DIRECTCOLOR) {
                depth = info->var.blue.length;
                if (info->var.red.length < depth)
                        depth = info->var.red.length;
                if (info->var.green.length < depth)
                        depth = info->var.green.length;
        }
//-------?--end
        if (info->fix.visual == FB_VISUAL_STATIC_PSEUDOCOLOR && depth > 4) {
                /* assume console colormap */
                depth = 4;
        }

        /* Return if no suitable logo was found */
        fb_logo.logo = fb_find_logo(depth);

上面这部分代码中

int depth = fb_get_color_depth(&info->var, &info->fix);

已经获取了色深在线面为什么还要

        if (info->flags & FBINFO_MISC_TILEBLITTING ||
            info->flags & FBINFO_MODULE)
                return 0;

        if (info->fix.visual == FB_VISUAL_DIRECTCOLOR) {
                depth = info->var.blue.length;
                if (info->var.red.length < depth)
                        depth = info->var.red.length;
                if (info->var.green.length < depth)
                        depth = info->var.green.length;
        }
//-------?--end
        if (info->fix.visual == FB_VISUAL_STATIC_PSEUDOCOLOR && depth > 4) {
                /* assume console colormap */
                depth = 4;
        }

有懂显示的大牛，麻烦解答一下