stderr_console.c

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#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/console.h>

#include "chan_user.h"

/* ----------------------------------------------------------------------------- */
/* trivial console driver -- simply dump everything to stderr                    */

/*
 * Don't register by default -- as this registers very early in the
 * boot process it becomes the default console.
 *
 * Initialized at init time.
 */
static int use_stderr_console = 0;

static void stderr_console_write(struct console *console, const char *string,
                 unsigned len)
{
    generic_write(2 /* stderr */, string, len, NULL);
}

static struct console stderr_console = {
    .name       = "stderr",
    .write      = stderr_console_write,
    .flags      = CON_PRINTBUFFER,
};

static int __init stderr_console_init(void)
{
    if (use_stderr_console)
        register_console(&stderr_console);
    return 0;
}
console_initcall(stderr_console_init);

static int stderr_setup(char *str)
{
    if (!str)
        return 0;
    use_stderr_console = simple_strtoul(str,&str,0);
    return 1;
}
__setup("stderr=", stderr_setup);

/* The previous behavior of not unregistering led to /dev/console being
 * impossible to open.  My FC5 filesystem started having init die, and the
 * system panicing because of this.  Unregistering causes the real
 * console to become the default console, and /dev/console can then be
 * opened.  Making this an initcall makes this happen late enough that
 * there is no added value in dumping everything to stderr, and the
 * normal console is good enough to show you all available output.
 */
static int __init unregister_stderr(void)
{
    unregister_console(&stderr_console);

    return 0;
}

__initcall(unregister_stderr);