root/arch/um/drivers/stderr_console.c

DEFINITIONS

1. stderr_console_write
2. stderr_console_init
3. stderr_setup
4. unregister_stderr

   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 
  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 
  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 
  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  */
  56 static int __init unregister_stderr(void)
  57 {
  58         unregister_console(&stderr_console);
  59 
  60         return 0;
  61 }
  62 
  63 __initcall(unregister_stderr);