early_printk.c

Go to the documentation of this file.

/*
 *  linux/arch/arm/kernel/early_printk.c
 *
 *  Copyright (C) 2009 Sascha Hauer <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/console.h>
#include <linux/init.h>

extern void printch(int);

static void early_write(const char *s, unsigned n)
{
    while (n-- > 0) {
        if (*s == '\n')
            printch('\r');
        printch(*s);
        s++;
    }
}

static void early_console_write(struct console *con, const char *s, unsigned n)
{
    early_write(s, n);
}

static struct console early_console = {
    .name =     "earlycon",
    .write =    early_console_write,
    .flags =    CON_PRINTBUFFER | CON_BOOT,
    .index =    -1,
};

asmlinkage void early_printk(const char *fmt, ...)
{
    char buf[512];
    int n;
    va_list ap;

    va_start(ap, fmt);
    n = vscnprintf(buf, sizeof(buf), fmt, ap);
    early_write(buf, n);
    va_end(ap);
}

static int __init setup_early_printk(char *buf)
{
    register_console(&early_console);
    return 0;
}

early_param("earlyprintk", setup_early_printk);