1 /* 2 * linux/arch/arm/kernel/early_printk.c 3 * 4 * Copyright (C) 2009 Sascha Hauer <s.hauer@pengutronix.de> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 */ 10 11 #include <linux/kernel.h> 12 #include <linux/console.h> 13 #include <linux/init.h> 14 15 extern void printch(int); 16 17 static void early_write(const char *s, unsigned n) 18 { 19 while (n-- > 0) { 20 if (*s == '\n') 21 printch('\r'); 22 printch(*s); 23 s++; 24 } 25 } 26 27 static void early_console_write(struct console *con, const char *s, unsigned n) 28 { 29 early_write(s, n); 30 } 31 32 static struct console early_console = { 33 .name = "earlycon", 34 .write = early_console_write, 35 .flags = CON_PRINTBUFFER | CON_BOOT, 36 .index = -1, 37 }; 38 39 asmlinkage void early_printk(const char *fmt, ...) 40 { 41 char buf[512]; 42 int n; 43 va_list ap; 44 45 va_start(ap, fmt); 46 n = vscnprintf(buf, sizeof(buf), fmt, ap); 47 early_write(buf, n); 48 va_end(ap); 49 } 50 51 static int __init setup_early_printk(char *buf) 52 { 53 register_console(&early_console); 54 return 0; 55 } 56 57 early_param("earlyprintk", setup_early_printk); 58