arch/um/drivers/stderr_console.c

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