kbleds.c

/*
 * kbleds.c - Blink keyboard leds until the module is unloaded.
 */

#include <linux/init.h>
#include <linux/kd.h> /* For KDSETLED */
#include <linux/module.h>
#include <linux/tty.h> /* For tty_struct */
#include <linux/vt.h> /* For MAX_NR_CONSOLES */
#include <linux/vt_kern.h> /* for fg_console */
#include <linux/console_struct.h> /* For vc_cons */

MODULE_DESCRIPTION("Example module illustrating the use of Keyboard LEDs.");

static struct timer_list my_timer;
static struct tty_driver *my_driver;
static unsigned long kbledstatus = 0;

#define BLINK_DELAY HZ / 5
#define ALL_LEDS_ON 0x07
#define RESTORE_LEDS 0xFF

/* Function my_timer_func blinks the keyboard LEDs periodically by invoking
 * command KDSETLED of ioctl() on the keyboard driver. To learn more on virtual
 * terminal ioctl operations, please see file:
 *   drivers/tty/vt/vt_ioctl.c, function vt_ioctl().
 *
 * The argument to KDSETLED is alternatively set to 7 (thus causing the led
 * mode to be set to LED_SHOW_IOCTL, and all the leds are lit) and to 0xFF
 * (any value above 7 switches back the led mode to LED_SHOW_FLAGS, thus
 * the LEDs reflect the actual keyboard status).  To learn more on this,
 * please see file: drivers/tty/vt/keyboard.c, function setledstate().
 */
static void my_timer_func(struct timer_list *unused)
{
    struct tty_struct *t = vc_cons[fg_console].d->port.tty;

    if (kbledstatus == ALL_LEDS_ON)
        kbledstatus = RESTORE_LEDS;
    else
        kbledstatus = ALL_LEDS_ON;

    (my_driver->ops->ioctl)(t, KDSETLED, kbledstatus);

    my_timer.expires = jiffies + BLINK_DELAY;
    add_timer(&my_timer);
}

static int __init kbleds_init(void)
{
    int i;

    pr_info("kbleds: loading\n");
    pr_info("kbleds: fgconsole is %x\n", fg_console);
    for (i = 0; i < MAX_NR_CONSOLES; i++) {
        if (!vc_cons[i].d)
            break;
        pr_info("poet_atkm: console[%i/%i] #%i, tty %p\n", i, MAX_NR_CONSOLES,
                vc_cons[i].d->vc_num, (void *)vc_cons[i].d->port.tty);
    }
    pr_info("kbleds: finished scanning consoles\n");

    my_driver = vc_cons[fg_console].d->port.tty->driver;
    pr_info("kbleds: tty driver name %s\n", my_driver->driver_name);

    /* Set up the LED blink timer the first time. */
    timer_setup(&my_timer, my_timer_func, 0);
    my_timer.expires = jiffies + BLINK_DELAY;
    add_timer(&my_timer);

    return 0;
}

static void __exit kbleds_cleanup(void)
{
    pr_info("kbleds: unloading...\n");
    del_timer(&my_timer);
    (my_driver->ops->ioctl)(vc_cons[fg_console].d->port.tty, KDSETLED,
                            RESTORE_LEDS);
}

module_init(kbleds_init);
module_exit(kbleds_cleanup);

MODULE_LICENSE("GPL");