speakup-test.c

#include <linux/module.h>    // included for all kernel modules
#include <linux/kernel.h>    // included for KERN_INFO
#include <linux/init.h>      // included for __init and __exit macros
#include <linux/tty.h>


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Okash");
MODULE_DESCRIPTION("Speakup Test");

static int speakup_test_open(struct tty_struct *tty)
{
    int rv;

    pr_warn("speakup_test_open(): tty->name: %s; tty->ldisc->ops->name: %s\n",
        tty->name, tty->ldisc->ops->name);
    rv = tty->ops->write(tty, "hi ldisc\n", 9);
    pr_warn("speakup_test_open(): done writing. rv=%d\n", rv);

    return 0;
}

static void speakup_test_close(struct tty_struct *tty)
{
    pr_warn("speakup_test_close()\n");
}

static struct tty_ldisc_ops hello_ldisc_ops = {
    .owner          = THIS_MODULE,
    .magic          = TTY_LDISC_MAGIC,
    .name           = "speakup_test_ldisc",
    .open           = speakup_test_open,
    .close          = speakup_test_close,
};

static struct tty_struct *tty;

static int __init speakup_test_init(void)
{
    int ret = 0;

    ret = tty_register_ldisc(N_SPEAKUP, &hello_ldisc_ops);
    if (ret) {
    pr_err("speakup_test_init(): Error registering line discipline.\n");
    return ret;
    }


    tty = tty_open_by_driver(MKDEV(4, 64), NULL, NULL);
    if (IS_ERR(tty))
        return PTR_ERR(tty);

    printk("got tty %p\n", tty);

    if (tty->ops->open)
        ret = tty->ops->open(tty, NULL);
    else
        ret = -ENODEV;

/* to be put in ldisc open */
    if (tty->ops->write == NULL)
        ret = -EOPNOTSUPP;
/* */

    if (ret) {
        tty_unlock(tty);
        return ret;
    }

    clear_bit(TTY_HUPPED, &tty->flags);
    tty_unlock(tty);

    tty_set_ldisc(tty, N_SPEAKUP);

    tty->ops->write(tty, "test\n", 5);

    return  ret;
}

static void __exit speakup_test_cleanup(void)
{
    /* Very much like tty_release, perhaps the tty_release code should be moved to a function which only takes (tty,filp) and we'd call it with (tty,NULL) */

    int idx;
    tty_lock(tty);
    idx = tty->index;

#if 0
    if (tty_release_checks(tty, idx)) {
            tty_unlock(tty);
            return 0;
    }
#endif

    if (tty->ops->close)
            tty->ops->close(tty, NULL);
    tty_unlock(tty);
#if 0
    tty_flush_works(tty);
#endif
#if 0
    mutex_lock(&tty_mutex);
    release_tty(tty, idx);
    mutex_unlock(&tty_mutex);
#endif

    printk("exit\n");
}

module_init(speakup_test_init);
module_exit(speakup_test_cleanup);