xref: /openbmc/linux/arch/um/drivers/stderr_console.c (revision b2441318)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/kernel.h>
3 #include <linux/init.h>
4 #include <linux/console.h>
5 
6 #include "chan_user.h"
7 
8 /* ----------------------------------------------------------------------------- */
9 /* trivial console driver -- simply dump everything to stderr                    */
10 
11 /*
12  * Don't register by default -- as this registers very early in the
13  * boot process it becomes the default console.
14  *
15  * Initialized at init time.
16  */
17 static int use_stderr_console = 0;
18 
stderr_console_write(struct console * console,const char * string,unsigned len)19 static void stderr_console_write(struct console *console, const char *string,
20 				 unsigned len)
21 {
22 	generic_write(2 /* stderr */, string, len, NULL);
23 }
24 
25 static struct console stderr_console = {
26 	.name		= "stderr",
27 	.write		= stderr_console_write,
28 	.flags		= CON_PRINTBUFFER,
29 };
30 
stderr_console_init(void)31 static int __init stderr_console_init(void)
32 {
33 	if (use_stderr_console)
34 		register_console(&stderr_console);
35 	return 0;
36 }
37 console_initcall(stderr_console_init);
38 
stderr_setup(char * str)39 static int stderr_setup(char *str)
40 {
41 	if (!str)
42 		return 0;
43 	use_stderr_console = simple_strtoul(str,&str,0);
44 	return 1;
45 }
46 __setup("stderr=", stderr_setup);
47 
48 /* The previous behavior of not unregistering led to /dev/console being
49  * impossible to open.  My FC5 filesystem started having init die, and the
50  * system panicing because of this.  Unregistering causes the real
51  * console to become the default console, and /dev/console can then be
52  * opened.  Making this an initcall makes this happen late enough that
53  * there is no added value in dumping everything to stderr, and the
54  * normal console is good enough to show you all available output.
55  */
unregister_stderr(void)56 static int __init unregister_stderr(void)
57 {
58 	unregister_console(&stderr_console);
59 
60 	return 0;
61 }
62 
63 __initcall(unregister_stderr);
64