early_printk.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 *    Copyright IBM Corp. 2017
 4 */
 5
 6#include <linux/console.h>
 7#include <linux/kernel.h>
 8#include <linux/init.h>
 9#include <asm/setup.h>
10#include <asm/sclp.h>
11
12static void sclp_early_write(struct console *con, const char *s, unsigned int len)
13{
14	__sclp_early_printk(s, len);
15}
16
17static struct console sclp_early_console = {
18	.name  = "earlysclp",
19	.write = sclp_early_write,
20	.flags = CON_PRINTBUFFER | CON_BOOT,
21	.index = -1,
22};
23
24void __init register_early_console(void)
25{
26	if (early_console)
27		return;
28	if (!sclp.has_linemode && !sclp.has_vt220)
29		return;
30	early_console = &sclp_early_console;
31	register_console(early_console);
32}
33
34static int __init setup_early_printk(char *buf)
35{
36	if (early_console)
37		return 0;
38	/* Accept only "earlyprintk" and "earlyprintk=sclp" */
39	if (buf && !str_has_prefix(buf, "sclp"))
40		return 0;
41	register_early_console();
42	return 0;
43}
44early_param("earlyprintk", setup_early_printk);