arm/kernel/early_printk.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  linux/arch/arm/kernel/early_printk.c
0004  *
0005  *  Copyright (C) 2009 Sascha Hauer <s.hauer@pengutronix.de>
0006  */
0007
0008 #include <linux/kernel.h>
0009 #include <linux/console.h>
0010 #include <linux/init.h>
0011 #include <linux/string.h>
0012
0013 extern void printascii(const char *);
0014
0015 static void early_write(const char *s, unsigned n)
0016 {
0017     char buf[128];
0018     while (n) {
0019         unsigned l = min(n, sizeof(buf)-1);
0020         memcpy(buf, s, l);
0021         buf[l] = 0;
0022         s += l;
0023         n -= l;
0024         printascii(buf);
0025     }
0026 }
0027
0028 static void early_console_write(struct console *con, const char *s, unsigned n)
0029 {
0030     early_write(s, n);
0031 }
0032
0033 static struct console early_console_dev = {
0034     .name =     "earlycon",
0035     .write =    early_console_write,
0036     .flags =    CON_PRINTBUFFER | CON_BOOT,
0037     .index =    -1,
0038 };
0039
0040 static int __init setup_early_printk(char *buf)
0041 {
0042     early_console = &early_console_dev;
0043     register_console(&early_console_dev);
0044     return 0;
0045 }
0046
0047 early_param("earlyprintk", setup_early_printk);