/*
 * Based on the same principle as kgdboe using the NETPOLL api, this
 * driver uses a console polling api to implement a gdb serial inteface
 * which is multiplexed on a console port.
 *
 * Maintainer: Jason Wessel <jason.wessel@windriver.com>
 *
 * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */
#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/kgdb.h>
#include <linux/kdb.h>
#include <linux/tty.h>
#include <linux/console.h>
#include <linux/vt_kern.h>
#include <linux/input.h>
#include <linux/module.h>

#define MAX_CONFIG_LEN          40

static struct kgdb_io           kgdboc_io_ops;

/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
static int configured           = -1;

static char config[MAX_CONFIG_LEN];
static struct kparam_string kps = {
        .string                 = config,
        .maxlen                 = MAX_CONFIG_LEN,
};

static int kgdboc_use_kms;  /* 1 if we use kernel mode switching */
static struct tty_driver        *kgdb_tty_driver;
static int                      kgdb_tty_line;

#ifdef CONFIG_KDB_KEYBOARD
static int kgdboc_reset_connect(struct input_handler *handler,
                                struct input_dev *dev,
                                const struct input_device_id *id)
{
        input_reset_device(dev);

        /* Return an error - we do not want to bind, just to reset */
        return -ENODEV;
}

static void kgdboc_reset_disconnect(struct input_handle *handle)
{
        /* We do not expect anyone to actually bind to us */
        BUG();
}

static const struct input_device_id kgdboc_reset_ids[] = {
        {
                .flags = INPUT_DEVICE_ID_MATCH_EVBIT,
                .evbit = { BIT_MASK(EV_KEY) },
        },
        { }
};

static struct input_handler kgdboc_reset_handler = {
        .connect        = kgdboc_reset_connect,
        .disconnect     = kgdboc_reset_disconnect,
        .name           = "kgdboc_reset",
        .id_table       = kgdboc_reset_ids,
};

static DEFINE_MUTEX(kgdboc_reset_mutex);

static void kgdboc_restore_input_helper(struct work_struct *dummy)
{
        /*
         * We need to take a mutex to prevent several instances of
         * this work running on different CPUs so they don't try
         * to register again already registered handler.
         */
        mutex_lock(&kgdboc_reset_mutex);

        if (input_register_handler(&kgdboc_reset_handler) == 0)
                input_unregister_handler(&kgdboc_reset_handler);

        mutex_unlock(&kgdboc_reset_mutex);
}

static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);

static void kgdboc_restore_input(void)
{
        if (likely(system_state == SYSTEM_RUNNING))
                schedule_work(&kgdboc_restore_input_work);
}

static int kgdboc_register_kbd(char **cptr)
{
        if (strncmp(*cptr, "kbd", 3) == 0 ||
                strncmp(*cptr, "kdb", 3) == 0) {
                if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
                        kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
                        kdb_poll_idx++;
                        if (cptr[0][3] == ',')
                                *cptr += 4;
                        else
                                return 1;
                }
        }
        return 0;
}

static void kgdboc_unregister_kbd(void)
{
        int i;

        for (i = 0; i < kdb_poll_idx; i++) {
                if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
                        kdb_poll_idx--;
                        kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
                        kdb_poll_funcs[kdb_poll_idx] = NULL;
                        i--;
                }
        }
        flush_work(&kgdboc_restore_input_work);
}
#else /* ! CONFIG_KDB_KEYBOARD */
#define kgdboc_register_kbd(x) 0
#define kgdboc_unregister_kbd()
#define kgdboc_restore_input()
#endif /* ! CONFIG_KDB_KEYBOARD */

static int kgdboc_option_setup(char *opt)
{
        if (strlen(opt) >= MAX_CONFIG_LEN) {
                printk(KERN_ERR "kgdboc: config string too long\n");
                return -ENOSPC;
        }
        strcpy(config, opt);

        return 0;
}

__setup("kgdboc=", kgdboc_option_setup);

static void cleanup_kgdboc(void)
{
        if (kgdb_unregister_nmi_console())
                return;
        kgdboc_unregister_kbd();
        if (configured == 1)
                kgdb_unregister_io_module(&kgdboc_io_ops);
}

static int configure_kgdboc(void)
{
        struct tty_driver *p;
        int tty_line = 0;
        int err;
        char *cptr = config;
        struct console *cons;

        err = kgdboc_option_setup(config);
        if (err || !strlen(config) || isspace(config[0]))
                goto noconfig;

        err = -ENODEV;
        kgdboc_io_ops.is_console = 0;
        kgdb_tty_driver = NULL;

        kgdboc_use_kms = 0;
        if (strncmp(cptr, "kms,", 4) == 0) {
                cptr += 4;
                kgdboc_use_kms = 1;
        }

        if (kgdboc_register_kbd(&cptr))
                goto do_register;

        p = tty_find_polling_driver(cptr, &tty_line);
        if (!p)
                goto noconfig;

        cons = console_drivers;
        while (cons) {
                int idx;
                if (cons->device && cons->device(cons, &idx) == p &&
                    idx == tty_line) {
                        kgdboc_io_ops.is_console = 1;
                        break;
                }
                cons = cons->next;
        }

        kgdb_tty_driver = p;
        kgdb_tty_line = tty_line;

do_register:
        err = kgdb_register_io_module(&kgdboc_io_ops);
        if (err)
                goto noconfig;

        err = kgdb_register_nmi_console();
        if (err)
                goto nmi_con_failed;

        configured = 1;

        return 0;

nmi_con_failed:
        kgdb_unregister_io_module(&kgdboc_io_ops);
noconfig:
        kgdboc_unregister_kbd();
        config[0] = 0;
        configured = 0;
        cleanup_kgdboc();

        return err;
}

static int __init init_kgdboc(void)
{
        /* Already configured? */
        if (configured == 1)
                return 0;

        return configure_kgdboc();
}

static int kgdboc_get_char(void)
{
        if (!kgdb_tty_driver)
                return -1;
        return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
                                                kgdb_tty_line);
}

static void kgdboc_put_char(u8 chr)
{
        if (!kgdb_tty_driver)
                return;
        kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
                                        kgdb_tty_line, chr);
}

static int param_set_kgdboc_var(const char *kmessage, struct kernel_param *kp)
{
        int len = strlen(kmessage);

        if (len >= MAX_CONFIG_LEN) {
                printk(KERN_ERR "kgdboc: config string too long\n");
                return -ENOSPC;
        }

        /* Only copy in the string if the init function has not run yet */
        if (configured < 0) {
                strcpy(config, kmessage);
                return 0;
        }

        if (kgdb_connected) {
                printk(KERN_ERR
                       "kgdboc: Cannot reconfigure while KGDB is connected.\n");

                return -EBUSY;
        }

        strcpy(config, kmessage);
        /* Chop out \n char as a result of echo */
        if (config[len - 1] == '\n')
                config[len - 1] = '\0';

        if (configured == 1)
                cleanup_kgdboc();

        /* Go and configure with the new params. */
        return configure_kgdboc();
}

static int dbg_restore_graphics;

static void kgdboc_pre_exp_handler(void)
{
        if (!dbg_restore_graphics && kgdboc_use_kms) {
                dbg_restore_graphics = 1;
                con_debug_enter(vc_cons[fg_console].d);
        }
        /* Increment the module count when the debugger is active */
        if (!kgdb_connected)
                try_module_get(THIS_MODULE);
}

static void kgdboc_post_exp_handler(void)
{
        /* decrement the module count when the debugger detaches */
        if (!kgdb_connected)
                module_put(THIS_MODULE);
        if (kgdboc_use_kms && dbg_restore_graphics) {
                dbg_restore_graphics = 0;
                con_debug_leave();
        }
        kgdboc_restore_input();
}

static struct kgdb_io kgdboc_io_ops = {
        .name                   = "kgdboc",
        .read_char              = kgdboc_get_char,
        .write_char             = kgdboc_put_char,
        .pre_exception          = kgdboc_pre_exp_handler,
        .post_exception         = kgdboc_post_exp_handler,
};

#ifdef CONFIG_KGDB_SERIAL_CONSOLE
/* This is only available if kgdboc is a built in for early debugging */
static int __init kgdboc_early_init(char *opt)
{
        /* save the first character of the config string because the
         * init routine can destroy it.
         */
        char save_ch;

        kgdboc_option_setup(opt);
        save_ch = config[0];
        init_kgdboc();
        config[0] = save_ch;
        return 0;
}

early_param("ekgdboc", kgdboc_early_init);
#endif /* CONFIG_KGDB_SERIAL_CONSOLE */

module_init(init_kgdboc);
module_exit(cleanup_kgdboc);
module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
MODULE_DESCRIPTION("KGDB Console TTY Driver");
MODULE_LICENSE("GPL");