[deliverable/linux.git] / drivers / tty / serial / kgdb_nmi.c

/*
 * KGDB NMI serial console
 *
 * Copyright 2010 Google, Inc.
 *		  Arve Hjønnevåg <arve@android.com>
 *		  Colin Cross <ccross@android.com>
 * Copyright 2012 Linaro Ltd.
 *		  Anton Vorontsov <anton.vorontsov@linaro.org>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/compiler.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/atomic.h>
#include <linux/console.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/interrupt.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include <linux/kfifo.h>
#include <linux/kgdb.h>
#include <linux/kdb.h>

static int kgdb_nmi_knock = 1;
module_param_named(knock, kgdb_nmi_knock, int, 0600);
MODULE_PARM_DESC(knock, "if set to 1 (default), the special '$3#33' command " \
			"must be used to enter the debugger; when set to 0, " \
			"hitting return key is enough to enter the debugger; " \
			"when set to -1, the debugger is entered immediately " \
			"upon NMI");

static char *kgdb_nmi_magic = "$3#33";
module_param_named(magic, kgdb_nmi_magic, charp, 0600);
MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)");

static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0);

static int kgdb_nmi_console_setup(struct console *co, char *options)
{
	arch_kgdb_ops.enable_nmi(1);

	/* The NMI console uses the dbg_io_ops to issue console messages. To
	 * avoid duplicate messages during kdb sessions we must inform kdb's
	 * I/O utilities that messages sent to the console will automatically
	 * be displayed on the dbg_io.
	 */
	dbg_io_ops->is_console = true;

	return 0;
}

static void kgdb_nmi_console_write(struct console *co, const char *s, uint c)
{
	int i;

	for (i = 0; i < c; i++)
		dbg_io_ops->write_char(s[i]);
}

static struct tty_driver *kgdb_nmi_tty_driver;

static struct tty_driver *kgdb_nmi_console_device(struct console *co, int *idx)
{
	*idx = co->index;
	return kgdb_nmi_tty_driver;
}

static struct console kgdb_nmi_console = {
	.name	= "ttyNMI",
	.setup  = kgdb_nmi_console_setup,
	.write	= kgdb_nmi_console_write,
	.device	= kgdb_nmi_console_device,
	.flags	= CON_PRINTBUFFER | CON_ANYTIME,
	.index	= -1,
};

/*
 * This is usually the maximum rate on debug ports. We make fifo large enough
 * to make copy-pasting to the terminal usable.
 */
#define KGDB_NMI_BAUD		115200
#define KGDB_NMI_FIFO_SIZE	roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ)

struct kgdb_nmi_tty_priv {
	struct tty_port port;
	struct timer_list timer;
	STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo;
};

static struct tty_port *kgdb_nmi_port;

static void kgdb_tty_recv(int ch)
{
	struct kgdb_nmi_tty_priv *priv;
	char c = ch;

	if (!kgdb_nmi_port || ch < 0)
		return;
	/*
	 * Can't use port->tty->driver_data as tty might be not there. Timer
	 * will check for tty and will get the ref, but here we don't have to
	 * do that, and actually, we can't: we're in NMI context, no locks are
	 * possible.
	 */
	priv = container_of(kgdb_nmi_port, struct kgdb_nmi_tty_priv, port);
	kfifo_in(&priv->fifo, &c, 1);
}

static int kgdb_nmi_poll_one_knock(void)
{
	static int n;
	int c = -1;
	const char *magic = kgdb_nmi_magic;
	size_t m = strlen(magic);
	bool printch = 0;

	c = dbg_io_ops->read_char();
	if (c == NO_POLL_CHAR)
		return c;

	if (!kgdb_nmi_knock && (c == '\r' || c == '\n')) {
		return 1;
	} else if (c == magic[n]) {
		n = (n + 1) % m;
		if (!n)
			return 1;
		printch = 1;
	} else {
		n = 0;
	}

	if (atomic_read(&kgdb_nmi_num_readers)) {
		kgdb_tty_recv(c);
		return 0;
	}

	if (printch) {
		kdb_printf("%c", c);
		return 0;
	}

	kdb_printf("\r%s %s to enter the debugger> %*s",
		   kgdb_nmi_knock ? "Type" : "Hit",
		   kgdb_nmi_knock ? magic  : "<return>", (int)m, "");
	while (m--)
		kdb_printf("\b");
	return 0;
}

/**
 * kgdb_nmi_poll_knock - Check if it is time to enter the debugger
 *
 * "Serial ports are often noisy, especially when muxed over another port (we
 * often use serial over the headset connector). Noise on the async command
 * line just causes characters that are ignored, on a command line that blocked
 * execution noise would be catastrophic." -- Colin Cross
 *
 * So, this function implements KGDB/KDB knocking on the serial line: we won't
 * enter the debugger until we receive a known magic phrase (which is actually
 * "$3#33", known as "escape to KDB" command. There is also a relaxed variant
 * of knocking, i.e. just pressing the return key is enough to enter the
 * debugger. And if knocking is disabled, the function always returns 1.
 */
bool kgdb_nmi_poll_knock(void)
{
	if (kgdb_nmi_knock < 0)
		return true;

	while (1) {
		int ret;

		ret = kgdb_nmi_poll_one_knock();
		if (ret == NO_POLL_CHAR)
			return false;
		else if (ret == 1)
			break;
	}
	return true;
}

/*
 * The tasklet is cheap, it does not cause wakeups when reschedules itself,
 * instead it waits for the next tick.
 */
static void kgdb_nmi_tty_receiver(unsigned long data)
{
	struct kgdb_nmi_tty_priv *priv = (void *)data;
	char ch;

	priv->timer.expires = jiffies + (HZ/100);
	add_timer(&priv->timer);

	if (likely(!atomic_read(&kgdb_nmi_num_readers) ||
		   !kfifo_len(&priv->fifo)))
		return;

	while (kfifo_out(&priv->fifo, &ch, 1))
		tty_insert_flip_char(&priv->port, ch, TTY_NORMAL);
	tty_flip_buffer_push(&priv->port);
}

static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty)
{
	struct kgdb_nmi_tty_priv *priv =
	    container_of(port, struct kgdb_nmi_tty_priv, port);

	kgdb_nmi_port = port;
	priv->timer.expires = jiffies + (HZ/100);
	add_timer(&priv->timer);

	return 0;
}

static void kgdb_nmi_tty_shutdown(struct tty_port *port)
{
	struct kgdb_nmi_tty_priv *priv =
	    container_of(port, struct kgdb_nmi_tty_priv, port);

	del_timer(&priv->timer);
	kgdb_nmi_port = NULL;
}

static const struct tty_port_operations kgdb_nmi_tty_port_ops = {
	.activate	= kgdb_nmi_tty_activate,
	.shutdown	= kgdb_nmi_tty_shutdown,
};

static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty)
{
	struct kgdb_nmi_tty_priv *priv;
	int ret;

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	INIT_KFIFO(priv->fifo);
	setup_timer(&priv->timer, kgdb_nmi_tty_receiver, (unsigned long)priv);
	tty_port_init(&priv->port);
	priv->port.ops = &kgdb_nmi_tty_port_ops;
	tty->driver_data = priv;

	ret = tty_port_install(&priv->port, drv, tty);
	if (ret) {
		pr_err("%s: can't install tty port: %d\n", __func__, ret);
		goto err;
	}
	return 0;
err:
	tty_port_destroy(&priv->port);
	kfree(priv);
	return ret;
}

static void kgdb_nmi_tty_cleanup(struct tty_struct *tty)
{
	struct kgdb_nmi_tty_priv *priv = tty->driver_data;

	tty->driver_data = NULL;
	tty_port_destroy(&priv->port);
	kfree(priv);
}

static int kgdb_nmi_tty_open(struct tty_struct *tty, struct file *file)
{
	struct kgdb_nmi_tty_priv *priv = tty->driver_data;
	unsigned int mode = file->f_flags & O_ACCMODE;
	int ret;

	ret = tty_port_open(&priv->port, tty, file);
	if (!ret && (mode == O_RDONLY || mode == O_RDWR))
		atomic_inc(&kgdb_nmi_num_readers);

	return ret;
}

static void kgdb_nmi_tty_close(struct tty_struct *tty, struct file *file)
{
	struct kgdb_nmi_tty_priv *priv = tty->driver_data;
	unsigned int mode = file->f_flags & O_ACCMODE;

	if (mode == O_RDONLY || mode == O_RDWR)
		atomic_dec(&kgdb_nmi_num_readers);

	tty_port_close(&priv->port, tty, file);
}

static void kgdb_nmi_tty_hangup(struct tty_struct *tty)
{
	struct kgdb_nmi_tty_priv *priv = tty->driver_data;

	tty_port_hangup(&priv->port);
}

static int kgdb_nmi_tty_write_room(struct tty_struct *tty)
{
	/* Actually, we can handle any amount as we use polled writes. */
	return 2048;
}

static int kgdb_nmi_tty_write(struct tty_struct *tty, const unchar *buf, int c)
{
	int i;

	for (i = 0; i < c; i++)
		dbg_io_ops->write_char(buf[i]);
	return c;
}

static const struct tty_operations kgdb_nmi_tty_ops = {
	.open		= kgdb_nmi_tty_open,
	.close		= kgdb_nmi_tty_close,
	.install	= kgdb_nmi_tty_install,
	.cleanup	= kgdb_nmi_tty_cleanup,
	.hangup		= kgdb_nmi_tty_hangup,
	.write_room	= kgdb_nmi_tty_write_room,
	.write		= kgdb_nmi_tty_write,
};

int kgdb_register_nmi_console(void)
{
	int ret;

	if (!arch_kgdb_ops.enable_nmi)
		return 0;

	kgdb_nmi_tty_driver = alloc_tty_driver(1);
	if (!kgdb_nmi_tty_driver) {
		pr_err("%s: cannot allocate tty\n", __func__);
		return -ENOMEM;
	}
	kgdb_nmi_tty_driver->driver_name	= "ttyNMI";
	kgdb_nmi_tty_driver->name		= "ttyNMI";
	kgdb_nmi_tty_driver->num		= 1;
	kgdb_nmi_tty_driver->type		= TTY_DRIVER_TYPE_SERIAL;
	kgdb_nmi_tty_driver->subtype		= SERIAL_TYPE_NORMAL;
	kgdb_nmi_tty_driver->flags		= TTY_DRIVER_REAL_RAW;
	kgdb_nmi_tty_driver->init_termios	= tty_std_termios;
	tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios,
				     KGDB_NMI_BAUD, KGDB_NMI_BAUD);
	tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops);

	ret = tty_register_driver(kgdb_nmi_tty_driver);
	if (ret) {
		pr_err("%s: can't register tty driver: %d\n", __func__, ret);
		goto err_drv_reg;
	}

	register_console(&kgdb_nmi_console);

	return 0;
err_drv_reg:
	put_tty_driver(kgdb_nmi_tty_driver);
	return ret;
}
EXPORT_SYMBOL_GPL(kgdb_register_nmi_console);

int kgdb_unregister_nmi_console(void)
{
	int ret;

	if (!arch_kgdb_ops.enable_nmi)
		return 0;
	arch_kgdb_ops.enable_nmi(0);

	ret = unregister_console(&kgdb_nmi_console);
	if (ret)
		return ret;

	ret = tty_unregister_driver(kgdb_nmi_tty_driver);
	if (ret)
		return ret;
	put_tty_driver(kgdb_nmi_tty_driver);

	return 0;
}
EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console);
Commit	Line	Data
0c57dfcc AV	1	/*
	2	* KGDB NMI serial console
	3	*
	4	* Copyright 2010 Google, Inc.
	5	* Arve Hjønnevåg <arve@android.com>
	6	* Colin Cross <ccross@android.com>
	7	* Copyright 2012 Linaro Ltd.
	8	* Anton Vorontsov <anton.vorontsov@linaro.org>
	9	*
	10	* This program is free software; you can redistribute it and/or modify it
	11	* under the terms of the GNU General Public License version 2 as published
	12	* by the Free Software Foundation.
	13	*/
	14
	15	#include <linux/kernel.h>
	16	#include <linux/module.h>
	17	#include <linux/compiler.h>
0c57dfcc AV	18	#include <linux/slab.h>
	19	#include <linux/errno.h>
	20	#include <linux/atomic.h>
	21	#include <linux/console.h>
	22	#include <linux/tty.h>
	23	#include <linux/tty_driver.h>
	24	#include <linux/tty_flip.h>
16559ae4	25	#include <linux/serial_core.h>
0c57dfcc AV	26	#include <linux/interrupt.h>
	27	#include <linux/hrtimer.h>
	28	#include <linux/tick.h>
	29	#include <linux/kfifo.h>
	30	#include <linux/kgdb.h>
	31	#include <linux/kdb.h>
	32
	33	static int kgdb_nmi_knock = 1;
	34	module_param_named(knock, kgdb_nmi_knock, int, 0600);
	35	MODULE_PARM_DESC(knock, "if set to 1 (default), the special '$3#33' command " \
	36	"must be used to enter the debugger; when set to 0, " \
	37	"hitting return key is enough to enter the debugger; " \
	38	"when set to -1, the debugger is entered immediately " \
	39	"upon NMI");
	40
	41	static char *kgdb_nmi_magic = "$3#33";
	42	module_param_named(magic, kgdb_nmi_magic, charp, 0600);
	43	MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)");
	44
c8b29f04	45	static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0);
0c57dfcc	46
bd71a1c0 DT	47	static int kgdb_nmi_console_setup(struct console co, char options)
bd71a1c0 DT	48	{
287f03c0 DT	49	arch_kgdb_ops.enable_nmi(1);
287f03c0 DT	50
bd71a1c0 DT	51	/* The NMI console uses the dbg_io_ops to issue console messages. To
	52	* avoid duplicate messages during kdb sessions we must inform kdb's
	53	* I/O utilities that messages sent to the console will automatically
	54	* be displayed on the dbg_io.
	55	*/
	56	dbg_io_ops->is_console = true;
	57
	58	return 0;
	59	}
	60
0c57dfcc AV	61	static void kgdb_nmi_console_write(struct console co, const char s, uint c)
	62	{
	63	int i;
	64
0c57dfcc AV	65	for (i = 0; i < c; i++)
	66	dbg_io_ops->write_char(s[i]);
	67	}
	68
	69	static struct tty_driver *kgdb_nmi_tty_driver;
	70
	71	static struct tty_driver kgdb_nmi_console_device(struct console co, int *idx)
	72	{
	73	*idx = co->index;
	74	return kgdb_nmi_tty_driver;
	75	}
	76
	77	static struct console kgdb_nmi_console = {
	78	.name = "ttyNMI",
bd71a1c0	79	.setup = kgdb_nmi_console_setup,
0c57dfcc AV	80	.write = kgdb_nmi_console_write,
0c57dfcc AV	81	.device = kgdb_nmi_console_device,
287f03c0	82	.flags = CON_PRINTBUFFER \| CON_ANYTIME,
0c57dfcc AV	83	.index = -1,
	84	};
	85
	86	/*
	87	* This is usually the maximum rate on debug ports. We make fifo large enough
	88	* to make copy-pasting to the terminal usable.
	89	*/
	90	#define KGDB_NMI_BAUD 115200
	91	#define KGDB_NMI_FIFO_SIZE roundup_pow_of_two(KGDB_NMI_BAUD / 8 / HZ)
	92
	93	struct kgdb_nmi_tty_priv {
	94	struct tty_port port;
8a0ff60f	95	struct timer_list timer;
0c57dfcc AV	96	STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo;
	97	};
	98
0c57dfcc AV	99	static struct tty_port *kgdb_nmi_port;
	100
	101	static void kgdb_tty_recv(int ch)
	102	{
	103	struct kgdb_nmi_tty_priv *priv;
	104	char c = ch;
	105
	106	if (!kgdb_nmi_port \|\| ch < 0)
	107	return;
	108	/*
8a0ff60f	109	* Can't use port->tty->driver_data as tty might be not there. Timer
0c57dfcc AV	110	* will check for tty and will get the ref, but here we don't have to
	111	* do that, and actually, we can't: we're in NMI context, no locks are
	112	* possible.
	113	*/
06d18289	114	priv = container_of(kgdb_nmi_port, struct kgdb_nmi_tty_priv, port);
0c57dfcc	115	kfifo_in(&priv->fifo, &c, 1);
0c57dfcc AV	116	}
	117
	118	static int kgdb_nmi_poll_one_knock(void)
	119	{
	120	static int n;
	121	int c = -1;
	122	const char *magic = kgdb_nmi_magic;
	123	size_t m = strlen(magic);
	124	bool printch = 0;
	125
	126	c = dbg_io_ops->read_char();
	127	if (c == NO_POLL_CHAR)
	128	return c;
	129
	130	if (!kgdb_nmi_knock && (c == '\r' \|\| c == '\n')) {
	131	return 1;
	132	} else if (c == magic[n]) {
	133	n = (n + 1) % m;
	134	if (!n)
	135	return 1;
	136	printch = 1;
	137	} else {
	138	n = 0;
	139	}
	140
c8b29f04	141	if (atomic_read(&kgdb_nmi_num_readers)) {
0c57dfcc AV	142	kgdb_tty_recv(c);
	143	return 0;
	144	}
	145
	146	if (printch) {
	147	kdb_printf("%c", c);
	148	return 0;
	149	}
	150
	151	kdb_printf("\r%s %s to enter the debugger> %*s",
	152	kgdb_nmi_knock ? "Type" : "Hit",
	153	kgdb_nmi_knock ? magic : "<return>", (int)m, "");
	154	while (m--)
	155	kdb_printf("\b");
	156	return 0;
	157	}
	158
	159	/**
	160	* kgdb_nmi_poll_knock - Check if it is time to enter the debugger
	161	*
	162	* "Serial ports are often noisy, especially when muxed over another port (we
	163	* often use serial over the headset connector). Noise on the async command
	164	* line just causes characters that are ignored, on a command line that blocked
	165	* execution noise would be catastrophic." -- Colin Cross
	166	*
	167	* So, this function implements KGDB/KDB knocking on the serial line: we won't
	168	* enter the debugger until we receive a known magic phrase (which is actually
	169	* "$3#33", known as "escape to KDB" command. There is also a relaxed variant
	170	* of knocking, i.e. just pressing the return key is enough to enter the
	171	* debugger. And if knocking is disabled, the function always returns 1.
	172	*/
	173	bool kgdb_nmi_poll_knock(void)
	174	{
	175	if (kgdb_nmi_knock < 0)
cbc7f6bd	176	return true;
0c57dfcc AV	177
	178	while (1) {
	179	int ret;
	180
	181	ret = kgdb_nmi_poll_one_knock();
	182	if (ret == NO_POLL_CHAR)
cbc7f6bd	183	return false;
0c57dfcc AV	184	else if (ret == 1)
	185	break;
	186	}
cbc7f6bd	187	return true;
0c57dfcc AV	188	}
	189
	190	/*
	191	* The tasklet is cheap, it does not cause wakeups when reschedules itself,
	192	* instead it waits for the next tick.
	193	*/
	194	static void kgdb_nmi_tty_receiver(unsigned long data)
	195	{
	196	struct kgdb_nmi_tty_priv priv = (void )data;
0c57dfcc AV	197	char ch;
0c57dfcc AV	198
8a0ff60f DT	199	priv->timer.expires = jiffies + (HZ/100);
8a0ff60f DT	200	add_timer(&priv->timer);
0c57dfcc	201
c8b29f04 DT	202	if (likely(!atomic_read(&kgdb_nmi_num_readers) \|\|
c8b29f04 DT	203	!kfifo_len(&priv->fifo)))
0c57dfcc AV	204	return;
0c57dfcc AV	205
0c57dfcc	206	while (kfifo_out(&priv->fifo, &ch, 1))
92a19f9c	207	tty_insert_flip_char(&priv->port, ch, TTY_NORMAL);
2e124b4a	208	tty_flip_buffer_push(&priv->port);
0c57dfcc AV	209	}
	210
	211	static int kgdb_nmi_tty_activate(struct tty_port port, struct tty_struct tty)
	212	{
06d18289 DT	213	struct kgdb_nmi_tty_priv *priv =
06d18289 DT	214	container_of(port, struct kgdb_nmi_tty_priv, port);
0c57dfcc AV	215
0c57dfcc AV	216	kgdb_nmi_port = port;
8a0ff60f DT	217	priv->timer.expires = jiffies + (HZ/100);
	218	add_timer(&priv->timer);
	219
0c57dfcc AV	220	return 0;
	221	}
	222
	223	static void kgdb_nmi_tty_shutdown(struct tty_port *port)
	224	{
06d18289 DT	225	struct kgdb_nmi_tty_priv *priv =
06d18289 DT	226	container_of(port, struct kgdb_nmi_tty_priv, port);
0c57dfcc	227
8a0ff60f	228	del_timer(&priv->timer);
0c57dfcc AV	229	kgdb_nmi_port = NULL;
	230	}
	231
	232	static const struct tty_port_operations kgdb_nmi_tty_port_ops = {
	233	.activate = kgdb_nmi_tty_activate,
	234	.shutdown = kgdb_nmi_tty_shutdown,
	235	};
	236
	237	static int kgdb_nmi_tty_install(struct tty_driver drv, struct tty_struct tty)
	238	{
	239	struct kgdb_nmi_tty_priv *priv;
	240	int ret;
	241
	242	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	243	if (!priv)
	244	return -ENOMEM;
	245
	246	INIT_KFIFO(priv->fifo);
8a0ff60f	247	setup_timer(&priv->timer, kgdb_nmi_tty_receiver, (unsigned long)priv);
0c57dfcc AV	248	tty_port_init(&priv->port);
	249	priv->port.ops = &kgdb_nmi_tty_port_ops;
	250	tty->driver_data = priv;
	251
	252	ret = tty_port_install(&priv->port, drv, tty);
	253	if (ret) {
	254	pr_err("%s: can't install tty port: %d\n", __func__, ret);
	255	goto err;
	256	}
	257	return 0;
	258	err:
191c5f10	259	tty_port_destroy(&priv->port);
0c57dfcc AV	260	kfree(priv);
	261	return ret;
	262	}
	263
	264	static void kgdb_nmi_tty_cleanup(struct tty_struct *tty)
	265	{
	266	struct kgdb_nmi_tty_priv *priv = tty->driver_data;
	267
	268	tty->driver_data = NULL;
191c5f10	269	tty_port_destroy(&priv->port);
0c57dfcc AV	270	kfree(priv);
	271	}
	272
	273	static int kgdb_nmi_tty_open(struct tty_struct tty, struct file file)
	274	{
	275	struct kgdb_nmi_tty_priv *priv = tty->driver_data;
c8b29f04 DT	276	unsigned int mode = file->f_flags & O_ACCMODE;
	277	int ret;
	278
	279	ret = tty_port_open(&priv->port, tty, file);
	280	if (!ret && (mode == O_RDONLY \|\| mode == O_RDWR))
	281	atomic_inc(&kgdb_nmi_num_readers);
0c57dfcc	282
c8b29f04	283	return ret;
0c57dfcc AV	284	}
	285
	286	static void kgdb_nmi_tty_close(struct tty_struct tty, struct file file)
	287	{
	288	struct kgdb_nmi_tty_priv *priv = tty->driver_data;
c8b29f04 DT	289	unsigned int mode = file->f_flags & O_ACCMODE;
	290
	291	if (mode == O_RDONLY \|\| mode == O_RDWR)
	292	atomic_dec(&kgdb_nmi_num_readers);
0c57dfcc AV	293
	294	tty_port_close(&priv->port, tty, file);
	295	}
	296
	297	static void kgdb_nmi_tty_hangup(struct tty_struct *tty)
	298	{
	299	struct kgdb_nmi_tty_priv *priv = tty->driver_data;
	300
	301	tty_port_hangup(&priv->port);
	302	}
	303
	304	static int kgdb_nmi_tty_write_room(struct tty_struct *tty)
	305	{
	306	/* Actually, we can handle any amount as we use polled writes. */
	307	return 2048;
	308	}
	309
	310	static int kgdb_nmi_tty_write(struct tty_struct tty, const unchar buf, int c)
	311	{
	312	int i;
	313
	314	for (i = 0; i < c; i++)
	315	dbg_io_ops->write_char(buf[i]);
	316	return c;
	317	}
	318
	319	static const struct tty_operations kgdb_nmi_tty_ops = {
	320	.open = kgdb_nmi_tty_open,
	321	.close = kgdb_nmi_tty_close,
	322	.install = kgdb_nmi_tty_install,
	323	.cleanup = kgdb_nmi_tty_cleanup,
	324	.hangup = kgdb_nmi_tty_hangup,
	325	.write_room = kgdb_nmi_tty_write_room,
	326	.write = kgdb_nmi_tty_write,
	327	};
	328
0c57dfcc AV	329	int kgdb_register_nmi_console(void)
	330	{
	331	int ret;
	332
	333	if (!arch_kgdb_ops.enable_nmi)
	334	return 0;
	335
	336	kgdb_nmi_tty_driver = alloc_tty_driver(1);
	337	if (!kgdb_nmi_tty_driver) {
	338	pr_err("%s: cannot allocate tty\n", __func__);
	339	return -ENOMEM;
	340	}
	341	kgdb_nmi_tty_driver->driver_name = "ttyNMI";
	342	kgdb_nmi_tty_driver->name = "ttyNMI";
	343	kgdb_nmi_tty_driver->num = 1;
	344	kgdb_nmi_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
	345	kgdb_nmi_tty_driver->subtype = SERIAL_TYPE_NORMAL;
	346	kgdb_nmi_tty_driver->flags = TTY_DRIVER_REAL_RAW;
	347	kgdb_nmi_tty_driver->init_termios = tty_std_termios;
	348	tty_termios_encode_baud_rate(&kgdb_nmi_tty_driver->init_termios,
	349	KGDB_NMI_BAUD, KGDB_NMI_BAUD);
	350	tty_set_operations(kgdb_nmi_tty_driver, &kgdb_nmi_tty_ops);
	351
	352	ret = tty_register_driver(kgdb_nmi_tty_driver);
	353	if (ret) {
	354	pr_err("%s: can't register tty driver: %d\n", __func__, ret);
	355	goto err_drv_reg;
	356	}
	357
0c57dfcc	358	register_console(&kgdb_nmi_console);
0c57dfcc AV	359
0c57dfcc AV	360	return 0;
0c57dfcc AV	361	err_drv_reg:
	362	put_tty_driver(kgdb_nmi_tty_driver);
	363	return ret;
	364	}
	365	EXPORT_SYMBOL_GPL(kgdb_register_nmi_console);
	366
	367	int kgdb_unregister_nmi_console(void)
	368	{
	369	int ret;
	370
	371	if (!arch_kgdb_ops.enable_nmi)
	372	return 0;
	373	arch_kgdb_ops.enable_nmi(0);
	374
0c57dfcc AV	375	ret = unregister_console(&kgdb_nmi_console);
	376	if (ret)
	377	return ret;
	378
	379	ret = tty_unregister_driver(kgdb_nmi_tty_driver);
	380	if (ret)
	381	return ret;
	382	put_tty_driver(kgdb_nmi_tty_driver);
	383
	384	return 0;
	385	}
	386	EXPORT_SYMBOL_GPL(kgdb_unregister_nmi_console);