1. 根目录:
2. arch
3. x86
4. platform
5. efi
6. early_printk.c

/*
 * Copyright (C) 2013 Intel Corporation; author Matt Fleming
 *
 *  This file is part of the Linux kernel, and is made available under
 *  the terms of the GNU General Public License version 2.
 */

#include <linux/console.h>
#include <linux/efi.h>
#include <linux/font.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <asm/setup.h>

static const struct font_desc *font;
static u32 efi_x, efi_y;

static __init void early_efi_clear_scanline(unsigned int y)
{
	unsigned long base, *dst;
	u16 len;

	base = boot_params.screen_info.lfb_base;
	len = boot_params.screen_info.lfb_linelength;

	dst = early_ioremap(base + y*len, len);
	if (!dst)
		return;

	memset(dst, 0, len);
	early_iounmap(dst, len);
}

static __init void early_efi_scroll_up(void)
{
	unsigned long base, *dst, *src;
	u16 len;
	u32 i, height;

	base = boot_params.screen_info.lfb_base;
	len = boot_params.screen_info.lfb_linelength;
	height = boot_params.screen_info.lfb_height;

	for (i = 0; i < height - font->height; i++) {
		dst = early_ioremap(base + i*len, len);
		if (!dst)
			return;

		src = early_ioremap(base + (i + font->height) * len, len);
		if (!src) {
			early_iounmap(dst, len);
			return;
		}

		memmove(dst, src, len);

		early_iounmap(src, len);
		early_iounmap(dst, len);
	}
}

static void early_efi_write_char(u32 *dst, unsigned char c, unsigned int h)
{
	const u32 color_black = 0x00000000;
	const u32 color_white = 0x00ffffff;
	const u8 *src;
	u8 s8;
	int m;

	src = font->data + c * font->height;
	s8 = *(src + h);

	for (m = 0; m < 8; m++) {
		if ((s8 >> (7 - m)) & 1)
			*dst = color_white;
		else
			*dst = color_black;
		dst++;
	}
}

static __init void
early_efi_write(struct console *con, const char *str, unsigned int num)
{
	struct screen_info *si;
	unsigned long base;
	unsigned int len;
	const char *s;
	void *dst;

	base = boot_params.screen_info.lfb_base;
	si = &boot_params.screen_info;
	len = si->lfb_linelength;

	while (num) {
		unsigned int linemax;
		unsigned int h, count = 0;

		for (s = str; *s && *s != '\n'; s++) {
			if (count == num)
				break;
			count++;
		}

		linemax = (si->lfb_width - efi_x) / font->width;
		if (count > linemax)
			count = linemax;

		for (h = 0; h < font->height; h++) {
			unsigned int n, x;

			dst = early_ioremap(base + (efi_y + h) * len, len);
			if (!dst)
				return;

			s = str;
			n = count;
			x = efi_x;

			while (n-- > 0) {
				early_efi_write_char(dst + x*4, *s, h);
				x += font->width;
				s++;
			}

			early_iounmap(dst, len);
		}

		num -= count;
		efi_x += count * font->width;
		str += count;

		if (num > 0 && *s == '\n') {
			efi_x = 0;
			efi_y += font->height;
			str++;
			num--;
		}

		if (efi_x >= si->lfb_width) {
			efi_x = 0;
			efi_y += font->height;
		}

		if (efi_y + font->height > si->lfb_height) {
			u32 i;

			efi_y -= font->height;
			early_efi_scroll_up();

			for (i = 0; i < font->height; i++)
				early_efi_clear_scanline(efi_y + i);
		}
	}
}

static __init int early_efi_setup(struct console *con, char *options)
{
	struct screen_info *si;
	u16 xres, yres;
	u32 i;

	si = &boot_params.screen_info;
	xres = si->lfb_width;
	yres = si->lfb_height;

	/*
	 * early_efi_write_char() implicitly assumes a framebuffer with
	 * 32-bits per pixel.
	 */
	if (si->lfb_depth != 32)
		return -ENODEV;

	font = get_default_font(xres, yres, -1, -1);
	if (!font)
		return -ENODEV;

	efi_y = rounddown(yres, font->height) - font->height;
	for (i = 0; i < (yres - efi_y) / font->height; i++)
		early_efi_scroll_up();

	return 0;
}

struct console early_efi_console = {
	.name =		"earlyefi",
	.write =	early_efi_write,
	.setup =	early_efi_setup,
	.flags =	CON_PRINTBUFFER,
	.index =	-1,
};