Linux开机液晶屏Logo显示：boot-logo bigger than screen

前不久，因为工作需要更换了液晶屏，分辨率由原来的800*480换成了800*600。

当然首先更改了液晶屏驱动，修改了相应的参数。把开机Logo也进行了更换，分辨率修改为800*600。

但是开机时，Logo无法显示，提示以下错误。

fbcon_init: disable boot-logo (boot-logo bigger than screen).

真是扯淡啊，查看源代码，该提示在drvers/video/console/Fbcon.c下，在此截取这段代码。

static void fbcon_prepare_logo(struct vc_data *vc, struct fb_info *info,
			       int cols, int rows, int new_cols, int new_rows)
{
	/* Need to make room for the logo */
	struct fbcon_ops *ops = info->fbcon_par;
	int cnt, erase = vc->vc_video_erase_char, step;
	unsigned short *save = NULL, *r, *q;
	int logo_height;

	if (info->flags & FBINFO_MODULE) {
		logo_shown = FBCON_LOGO_DONTSHOW;
		return;
	}

	/*
	 * remove underline attribute from erase character
	 * if black and white framebuffer.
	 */
	if (fb_get_color_depth(&info->var, &info->fix) == 1)
		erase &= ~0x400;
	logo_height = fb_prepare_logo(info, ops->rotate);
        
	//logo_lines在此赋值
	logo_lines = DIV_ROUND_UP(logo_height, vc->vc_font.height);
	q = (unsigned short *) (vc->vc_origin +
				vc->vc_size_row * rows);
	step = logo_lines * cols;
	for (r = q - logo_lines * cols; r < q; r++)
		if (scr_readw(r) != vc->vc_video_erase_char)
			break;
	if (r != q && new_rows >= rows + logo_lines) {
		save = kmalloc(logo_lines * new_cols * 2, GFP_KERNEL);
		if (save) {
			int i = cols < new_cols ? cols : new_cols;
			scr_memsetw(save, erase, logo_lines * new_cols * 2);
			r = q - step;
			for (cnt = 0; cnt < logo_lines; cnt++, r += i)
				scr_memcpyw(save + cnt * new_cols, r, 2 * i);
			r = q;
		}
	}
	if (r == q) {
		/* We can scroll screen down */
		r = q - step - cols;
		for (cnt = rows - logo_lines; cnt > 0; cnt--) {
			scr_memcpyw(r + step, r, vc->vc_size_row);
			r -= cols;
		}
		if (!save) {
			int lines;
			if (vc->vc_y + logo_lines >= rows)
				lines = rows - vc->vc_y - 1;
			else
				lines = logo_lines;
			vc->vc_y += lines;
			vc->vc_pos += lines * vc->vc_size_row;
		}
	}
	scr_memsetw((unsigned short *) vc->vc_origin,
		    erase,
		    vc->vc_size_row * logo_lines);

	if (CON_IS_VISIBLE(vc) && vc->vc_mode == KD_TEXT) {
		fbcon_clear_margins(vc, 0);
		update_screen(vc);
	}

	if (save) {
		q = (unsigned short *) (vc->vc_origin +
					vc->vc_size_row *
					rows);
		scr_memcpyw(q, save, logo_lines * new_cols * 2);
		vc->vc_y += logo_lines;
		vc->vc_pos += logo_lines * vc->vc_size_row;
		kfree(save);
	}

	//错误提示在此
	if (logo_lines > vc->vc_bottom) {
		logo_shown = FBCON_LOGO_CANSHOW;
		printk(KERN_INFO
		       "fbcon_init: disable boot-logo (boot-logo bigger than screen).\n");
	} else if (logo_shown != FBCON_LOGO_DONTSHOW) {
		logo_shown = FBCON_LOGO_DRAW;
		vc->vc_top = logo_lines;
	}
}

可以发现是因为logo_lines > vc->vc_bottom引起的。

其中logo_lines = DIV_ROUND_UP(logo_height, vc->vc_font.height);    //（DIV_ROUND_UP是向上取整的意思）

而vc->vc_bottom代码读下来为vc->vc_bottom  = info->var.yres/ vc->vc_font.height;

其关键就是vc->vc_font.height了，Linux下vc->vc_font.height默认为16，所以当液晶屏和Logo的分辨率都为800*600时，600/16无法整除，故取整logo_lines =38;  vc->vc_bottom = 37;提示错误无法显示。

只要把logo的改小一下，改为592，则logo_lines = 592/16=37；  vc->vc_bottom = 600/16=37；就可以正常显示了。

//~End