xref: /linux/arch/s390/kernel/early_printk.c (revision bde5d79d00255db609fe9d859eef8c7b6d38b137)
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 
12 static void sclp_early_write(struct console *con, const char *s, unsigned int len)
13 {
14 	__sclp_early_printk(s, len);
15 }
16 
17 static struct console sclp_early_console = {
18 	.name  = "earlysclp",
19 	.write = sclp_early_write,
20 	.flags = CON_PRINTBUFFER | CON_BOOT,
21 	.index = -1,
22 };
23 
24 void __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 
34 static 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 }
44 early_param("earlyprintk", setup_early_printk);
45