arch/arm/kernel/early_printk.c

   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);