arch/um/drivers/stderr_console.c

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