/*
   * 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
  ");
  		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
  ");
  		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.
  ");
  
  		return -EBUSY;
  	}
  
  	strcpy(config, kmessage);
  	/* Chop out 
   char as a result of echo */
  	if (config[len - 1] == '
  ')
  		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");