tty: move hvc drivers to drivers/tty/hvc/

As requested by Arnd Bergmann, the hvc drivers are now
moved to the drivers/tty/hvc/ directory.  The virtio_console.c driver
was also moved, as it required the hvc_console.h file to be able to be
built, and it really is a hvc driver.

Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 914 insertions, 0 deletions

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
new file mode 100644
index 00000000000..e9cba13ee80
--- /dev/null
+++ b/drivers/tty/hvc/hvc_console.c
@@ -0,0 +1,914 @@
+/*
+ * Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
+ * Copyright (C) 2001 Paul Mackerras <paulus@au.ibm.com>, IBM
+ * Copyright (C) 2004 Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp.
+ * Copyright (C) 2004 IBM Corporation
+ *
+ * Additional Author(s):
+ *  Ryan S. Arnold <rsa@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/console.h>
+#include <linux/cpumask.h>
+#include <linux/init.h>
+#include <linux/kbd_kern.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/major.h>
+#include <linux/sysrq.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/delay.h>
+#include <linux/freezer.h>
+#include <linux/slab.h>
+
+#include <asm/uaccess.h>
+
+#include "hvc_console.h"
+
+#define HVC_MAJOR	229
+#define HVC_MINOR	0
+
+/*
+ * Wait this long per iteration while trying to push buffered data to the
+ * hypervisor before allowing the tty to complete a close operation.
+ */
+#define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
+
+/*
+ * These sizes are most efficient for vio, because they are the
+ * native transfer size. We could make them selectable in the
+ * future to better deal with backends that want other buffer sizes.
+ */
+#define N_OUTBUF	16
+#define N_INBUF		16
+
+#define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
+
+static struct tty_driver *hvc_driver;
+static struct task_struct *hvc_task;
+
+/* Picks up late kicks after list walk but before schedule() */
+static int hvc_kicked;
+
+static int hvc_init(void);
+
+#ifdef CONFIG_MAGIC_SYSRQ
+static int sysrq_pressed;
+#endif
+
+/* dynamic list of hvc_struct instances */
+static LIST_HEAD(hvc_structs);
+
+/*
+ * Protect the list of hvc_struct instances from inserts and removals during
+ * list traversal.
+ */
+static DEFINE_SPINLOCK(hvc_structs_lock);
+
+/*
+ * This value is used to assign a tty->index value to a hvc_struct based
+ * upon order of exposure via hvc_probe(), when we can not match it to
+ * a console candidate registered with hvc_instantiate().
+ */
+static int last_hvc = -1;
+
+/*
+ * Do not call this function with either the hvc_structs_lock or the hvc_struct
+ * lock held.  If successful, this function increments the kref reference
+ * count against the target hvc_struct so it should be released when finished.
+ */
+static struct hvc_struct *hvc_get_by_index(int index)
+{
+	struct hvc_struct *hp;
+	unsigned long flags;
+
+	spin_lock(&hvc_structs_lock);
+
+	list_for_each_entry(hp, &hvc_structs, next) {
+		spin_lock_irqsave(&hp->lock, flags);
+		if (hp->index == index) {
+			kref_get(&hp->kref);
+			spin_unlock_irqrestore(&hp->lock, flags);
+			spin_unlock(&hvc_structs_lock);
+			return hp;
+		}
+		spin_unlock_irqrestore(&hp->lock, flags);
+	}
+	hp = NULL;
+
+	spin_unlock(&hvc_structs_lock);
+	return hp;
+}
+
+
+/*
+ * Initial console vtermnos for console API usage prior to full console
+ * initialization.  Any vty adapter outside this range will not have usable
+ * console interfaces but can still be used as a tty device.  This has to be
+ * static because kmalloc will not work during early console init.
+ */
+static const struct hv_ops *cons_ops[MAX_NR_HVC_CONSOLES];
+static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
+	{[0 ... MAX_NR_HVC_CONSOLES - 1] = -1};
+
+/*
+ * Console APIs, NOT TTY.  These APIs are available immediately when
+ * hvc_console_setup() finds adapters.
+ */
+
+static void hvc_console_print(struct console *co, const char *b,
+			      unsigned count)
+{
+	char c[N_OUTBUF] __ALIGNED__;
+	unsigned i = 0, n = 0;
+	int r, donecr = 0, index = co->index;
+
+	/* Console access attempt outside of acceptable console range. */
+	if (index >= MAX_NR_HVC_CONSOLES)
+		return;
+
+	/* This console adapter was removed so it is not usable. */
+	if (vtermnos[index] == -1)
+		return;
+
+	while (count > 0 || i > 0) {
+		if (count > 0 && i < sizeof(c)) {
+			if (b[n] == '\n' && !donecr) {
+				c[i++] = '\r';
+				donecr = 1;
+			} else {
+				c[i++] = b[n++];
+				donecr = 0;
+				--count;
+			}
+		} else {
+			r = cons_ops[index]->put_chars(vtermnos[index], c, i);
+			if (r <= 0) {
+				/* throw away chars on error */
+				i = 0;
+			} else if (r > 0) {
+				i -= r;
+				if (i > 0)
+					memmove(c, c+r, i);
+			}
+		}
+	}
+}
+
+static struct tty_driver *hvc_console_device(struct console *c, int *index)
+{
+	if (vtermnos[c->index] == -1)
+		return NULL;
+
+	*index = c->index;
+	return hvc_driver;
+}
+
+static int __init hvc_console_setup(struct console *co, char *options)
+{
+	if (co->index < 0 || co->index >= MAX_NR_HVC_CONSOLES)
+		return -ENODEV;
+
+	if (vtermnos[co->index] == -1)
+		return -ENODEV;
+
+	return 0;
+}
+
+static struct console hvc_console = {
+	.name		= "hvc",
+	.write		= hvc_console_print,
+	.device		= hvc_console_device,
+	.setup		= hvc_console_setup,
+	.flags		= CON_PRINTBUFFER,
+	.index		= -1,
+};
+
+/*
+ * Early console initialization.  Precedes driver initialization.
+ *
+ * (1) we are first, and the user specified another driver
+ * -- index will remain -1
+ * (2) we are first and the user specified no driver
+ * -- index will be set to 0, then we will fail setup.
+ * (3)  we are first and the user specified our driver
+ * -- index will be set to user specified driver, and we will fail
+ * (4) we are after driver, and this initcall will register us
+ * -- if the user didn't specify a driver then the console will match
+ *
+ * Note that for cases 2 and 3, we will match later when the io driver
+ * calls hvc_instantiate() and call register again.
+ */
+static int __init hvc_console_init(void)
+{
+	register_console(&hvc_console);
+	return 0;
+}
+console_initcall(hvc_console_init);
+
+/* callback when the kboject ref count reaches zero. */
+static void destroy_hvc_struct(struct kref *kref)
+{
+	struct hvc_struct *hp = container_of(kref, struct hvc_struct, kref);
+	unsigned long flags;
+
+	spin_lock(&hvc_structs_lock);
+
+	spin_lock_irqsave(&hp->lock, flags);
+	list_del(&(hp->next));
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	spin_unlock(&hvc_structs_lock);
+
+	kfree(hp);
+}
+
+/*
+ * hvc_instantiate() is an early console discovery method which locates
+ * consoles * prior to the vio subsystem discovering them.  Hotplugged
+ * vty adapters do NOT get an hvc_instantiate() callback since they
+ * appear after early console init.
+ */
+int hvc_instantiate(uint32_t vtermno, int index, const struct hv_ops *ops)
+{
+	struct hvc_struct *hp;
+
+	if (index < 0 || index >= MAX_NR_HVC_CONSOLES)
+		return -1;
+
+	if (vtermnos[index] != -1)
+		return -1;
+
+	/* make sure no no tty has been registered in this index */
+	hp = hvc_get_by_index(index);
+	if (hp) {
+		kref_put(&hp->kref, destroy_hvc_struct);
+		return -1;
+	}
+
+	vtermnos[index] = vtermno;
+	cons_ops[index] = ops;
+
+	/* reserve all indices up to and including this index */
+	if (last_hvc < index)
+		last_hvc = index;
+
+	/* if this index is what the user requested, then register
+	 * now (setup won't fail at this point).  It's ok to just
+	 * call register again if previously .setup failed.
+	 */
+	if (index == hvc_console.index)
+		register_console(&hvc_console);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hvc_instantiate);
+
+/* Wake the sleeping khvcd */
+void hvc_kick(void)
+{
+	hvc_kicked = 1;
+	wake_up_process(hvc_task);
+}
+EXPORT_SYMBOL_GPL(hvc_kick);
+
+static void hvc_unthrottle(struct tty_struct *tty)
+{
+	hvc_kick();
+}
+
+/*
+ * The TTY interface won't be used until after the vio layer has exposed the vty
+ * adapter to the kernel.
+ */
+static int hvc_open(struct tty_struct *tty, struct file * filp)
+{
+	struct hvc_struct *hp;
+	unsigned long flags;
+	int rc = 0;
+
+	/* Auto increments kref reference if found. */
+	if (!(hp = hvc_get_by_index(tty->index)))
+		return -ENODEV;
+
+	spin_lock_irqsave(&hp->lock, flags);
+	/* Check and then increment for fast path open. */
+	if (hp->count++ > 0) {
+		tty_kref_get(tty);
+		spin_unlock_irqrestore(&hp->lock, flags);
+		hvc_kick();
+		return 0;
+	} /* else count == 0 */
+
+	tty->driver_data = hp;
+
+	hp->tty = tty_kref_get(tty);
+
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	if (hp->ops->notifier_add)
+		rc = hp->ops->notifier_add(hp, hp->data);
+
+	/*
+	 * If the notifier fails we return an error.  The tty layer
+	 * will call hvc_close() after a failed open but we don't want to clean
+	 * up there so we'll clean up here and clear out the previously set
+	 * tty fields and return the kref reference.
+	 */
+	if (rc) {
+		spin_lock_irqsave(&hp->lock, flags);
+		hp->tty = NULL;
+		spin_unlock_irqrestore(&hp->lock, flags);
+		tty_kref_put(tty);
+		tty->driver_data = NULL;
+		kref_put(&hp->kref, destroy_hvc_struct);
+		printk(KERN_ERR "hvc_open: request_irq failed with rc %d.\n", rc);
+	}
+	/* Force wakeup of the polling thread */
+	hvc_kick();
+
+	return rc;
+}
+
+static void hvc_close(struct tty_struct *tty, struct file * filp)
+{
+	struct hvc_struct *hp;
+	unsigned long flags;
+
+	if (tty_hung_up_p(filp))
+		return;
+
+	/*
+	 * No driver_data means that this close was issued after a failed
+	 * hvc_open by the tty layer's release_dev() function and we can just
+	 * exit cleanly because the kref reference wasn't made.
+	 */
+	if (!tty->driver_data)
+		return;
+
+	hp = tty->driver_data;
+
+	spin_lock_irqsave(&hp->lock, flags);
+
+	if (--hp->count == 0) {
+		/* We are done with the tty pointer now. */
+		hp->tty = NULL;
+		spin_unlock_irqrestore(&hp->lock, flags);
+
+		if (hp->ops->notifier_del)
+			hp->ops->notifier_del(hp, hp->data);
+
+		/* cancel pending tty resize work */
+		cancel_work_sync(&hp->tty_resize);
+
+		/*
+		 * Chain calls chars_in_buffer() and returns immediately if
+		 * there is no buffered data otherwise sleeps on a wait queue
+		 * waking periodically to check chars_in_buffer().
+		 */
+		tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
+	} else {
+		if (hp->count < 0)
+			printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
+				hp->vtermno, hp->count);
+		spin_unlock_irqrestore(&hp->lock, flags);
+	}
+
+	tty_kref_put(tty);
+	kref_put(&hp->kref, destroy_hvc_struct);
+}
+
+static void hvc_hangup(struct tty_struct *tty)
+{
+	struct hvc_struct *hp = tty->driver_data;
+	unsigned long flags;
+	int temp_open_count;
+
+	if (!hp)
+		return;
+
+	/* cancel pending tty resize work */
+	cancel_work_sync(&hp->tty_resize);
+
+	spin_lock_irqsave(&hp->lock, flags);
+
+	/*
+	 * The N_TTY line discipline has problems such that in a close vs
+	 * open->hangup case this can be called after the final close so prevent
+	 * that from happening for now.
+	 */
+	if (hp->count <= 0) {
+		spin_unlock_irqrestore(&hp->lock, flags);
+		return;
+	}
+
+	temp_open_count = hp->count;
+	hp->count = 0;
+	hp->n_outbuf = 0;
+	hp->tty = NULL;
+
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	if (hp->ops->notifier_hangup)
+		hp->ops->notifier_hangup(hp, hp->data);
+
+	while(temp_open_count) {
+		--temp_open_count;
+		tty_kref_put(tty);
+		kref_put(&hp->kref, destroy_hvc_struct);
+	}
+}
+
+/*
+ * Push buffered characters whether they were just recently buffered or waiting
+ * on a blocked hypervisor.  Call this function with hp->lock held.
+ */
+static int hvc_push(struct hvc_struct *hp)
+{
+	int n;
+
+	n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
+	if (n <= 0) {
+		if (n == 0) {
+			hp->do_wakeup = 1;
+			return 0;
+		}
+		/* throw away output on error; this happens when
+		   there is no session connected to the vterm. */
+		hp->n_outbuf = 0;
+	} else
+		hp->n_outbuf -= n;
+	if (hp->n_outbuf > 0)
+		memmove(hp->outbuf, hp->outbuf + n, hp->n_outbuf);
+	else
+		hp->do_wakeup = 1;
+
+	return n;
+}
+
+static int hvc_write(struct tty_struct *tty, const unsigned char *buf, int count)
+{
+	struct hvc_struct *hp = tty->driver_data;
+	unsigned long flags;
+	int rsize, written = 0;
+
+	/* This write was probably executed during a tty close. */
+	if (!hp)
+		return -EPIPE;
+
+	if (hp->count <= 0)
+		return -EIO;
+
+	spin_lock_irqsave(&hp->lock, flags);
+
+	/* Push pending writes */
+	if (hp->n_outbuf > 0)
+		hvc_push(hp);
+
+	while (count > 0 && (rsize = hp->outbuf_size - hp->n_outbuf) > 0) {
+		if (rsize > count)
+			rsize = count;
+		memcpy(hp->outbuf + hp->n_outbuf, buf, rsize);
+		count -= rsize;
+		buf += rsize;
+		hp->n_outbuf += rsize;
+		written += rsize;
+		hvc_push(hp);
+	}
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	/*
+	 * Racy, but harmless, kick thread if there is still pending data.
+	 */
+	if (hp->n_outbuf)
+		hvc_kick();
+
+	return written;
+}
+
+/**
+ * hvc_set_winsz() - Resize the hvc tty terminal window.
+ * @work:	work structure.
+ *
+ * The routine shall not be called within an atomic context because it
+ * might sleep.
+ *
+ * Locking:	hp->lock
+ */
+static void hvc_set_winsz(struct work_struct *work)
+{
+	struct hvc_struct *hp;
+	unsigned long hvc_flags;
+	struct tty_struct *tty;
+	struct winsize ws;
+
+	hp = container_of(work, struct hvc_struct, tty_resize);
+
+	spin_lock_irqsave(&hp->lock, hvc_flags);
+	if (!hp->tty) {
+		spin_unlock_irqrestore(&hp->lock, hvc_flags);
+		return;
+	}
+	ws  = hp->ws;
+	tty = tty_kref_get(hp->tty);
+	spin_unlock_irqrestore(&hp->lock, hvc_flags);
+
+	tty_do_resize(tty, &ws);
+	tty_kref_put(tty);
+}
+
+/*
+ * This is actually a contract between the driver and the tty layer outlining
+ * how much write room the driver can guarantee will be sent OR BUFFERED.  This
+ * driver MUST honor the return value.
+ */
+static int hvc_write_room(struct tty_struct *tty)
+{
+	struct hvc_struct *hp = tty->driver_data;
+
+	if (!hp)
+		return -1;
+
+	return hp->outbuf_size - hp->n_outbuf;
+}
+
+static int hvc_chars_in_buffer(struct tty_struct *tty)
+{
+	struct hvc_struct *hp = tty->driver_data;
+
+	if (!hp)
+		return 0;
+	return hp->n_outbuf;
+}
+
+/*
+ * timeout will vary between the MIN and MAX values defined here.  By default
+ * and during console activity we will use a default MIN_TIMEOUT of 10.  When
+ * the console is idle, we increase the timeout value on each pass through
+ * msleep until we reach the max.  This may be noticeable as a brief (average
+ * one second) delay on the console before the console responds to input when
+ * there has been no input for some time.
+ */
+#define MIN_TIMEOUT		(10)
+#define MAX_TIMEOUT		(2000)
+static u32 timeout = MIN_TIMEOUT;
+
+#define HVC_POLL_READ	0x00000001
+#define HVC_POLL_WRITE	0x00000002
+
+int hvc_poll(struct hvc_struct *hp)
+{
+	struct tty_struct *tty;
+	int i, n, poll_mask = 0;
+	char buf[N_INBUF] __ALIGNED__;
+	unsigned long flags;
+	int read_total = 0;
+	int written_total = 0;
+
+	spin_lock_irqsave(&hp->lock, flags);
+
+	/* Push pending writes */
+	if (hp->n_outbuf > 0)
+		written_total = hvc_push(hp);
+
+	/* Reschedule us if still some write pending */
+	if (hp->n_outbuf > 0) {
+		poll_mask |= HVC_POLL_WRITE;
+		/* If hvc_push() was not able to write, sleep a few msecs */
+		timeout = (written_total) ? 0 : MIN_TIMEOUT;
+	}
+
+	/* No tty attached, just skip */
+	tty = tty_kref_get(hp->tty);
+	if (tty == NULL)
+		goto bail;
+
+	/* Now check if we can get data (are we throttled ?) */
+	if (test_bit(TTY_THROTTLED, &tty->flags))
+		goto throttled;
+
+	/* If we aren't notifier driven and aren't throttled, we always
+	 * request a reschedule
+	 */
+	if (!hp->irq_requested)
+		poll_mask |= HVC_POLL_READ;
+
+	/* Read data if any */
+	for (;;) {
+		int count = tty_buffer_request_room(tty, N_INBUF);
+
+		/* If flip is full, just reschedule a later read */
+		if (count == 0) {
+			poll_mask |= HVC_POLL_READ;
+			break;
+		}
+
+		n = hp->ops->get_chars(hp->vtermno, buf, count);
+		if (n <= 0) {
+			/* Hangup the tty when disconnected from host */
+			if (n == -EPIPE) {
+				spin_unlock_irqrestore(&hp->lock, flags);
+				tty_hangup(tty);
+				spin_lock_irqsave(&hp->lock, flags);
+			} else if ( n == -EAGAIN ) {
+				/*
+				 * Some back-ends can only ensure a certain min
+				 * num of bytes read, which may be > 'count'.
+				 * Let the tty clear the flip buff to make room.
+				 */
+				poll_mask |= HVC_POLL_READ;
+			}
+			break;
+		}
+		for (i = 0; i < n; ++i) {
+#ifdef CONFIG_MAGIC_SYSRQ
+			if (hp->index == hvc_console.index) {
+				/* Handle the SysRq Hack */
+				/* XXX should support a sequence */
+				if (buf[i] == '\x0f') {	/* ^O */
+					/* if ^O is pressed again, reset
+					 * sysrq_pressed and flip ^O char */
+					sysrq_pressed = !sysrq_pressed;
+					if (sysrq_pressed)
+						continue;
+				} else if (sysrq_pressed) {
+					handle_sysrq(buf[i]);
+					sysrq_pressed = 0;
+					continue;
+				}
+			}
+#endif /* CONFIG_MAGIC_SYSRQ */
+			tty_insert_flip_char(tty, buf[i], 0);
+		}
+
+		read_total += n;
+	}
+ throttled:
+	/* Wakeup write queue if necessary */
+	if (hp->do_wakeup) {
+		hp->do_wakeup = 0;
+		tty_wakeup(tty);
+	}
+ bail:
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	if (read_total) {
+		/* Activity is occurring, so reset the polling backoff value to
+		   a minimum for performance. */
+		timeout = MIN_TIMEOUT;
+
+		tty_flip_buffer_push(tty);
+	}
+	if (tty)
+		tty_kref_put(tty);
+
+	return poll_mask;
+}
+EXPORT_SYMBOL_GPL(hvc_poll);
+
+/**
+ * __hvc_resize() - Update terminal window size information.
+ * @hp:		HVC console pointer
+ * @ws:		Terminal window size structure
+ *
+ * Stores the specified window size information in the hvc structure of @hp.
+ * The function schedule the tty resize update.
+ *
+ * Locking:	Locking free; the function MUST be called holding hp->lock
+ */
+void __hvc_resize(struct hvc_struct *hp, struct winsize ws)
+{
+	hp->ws = ws;
+	schedule_work(&hp->tty_resize);
+}
+EXPORT_SYMBOL_GPL(__hvc_resize);
+
+/*
+ * This kthread is either polling or interrupt driven.  This is determined by
+ * calling hvc_poll() who determines whether a console adapter support
+ * interrupts.
+ */
+static int khvcd(void *unused)
+{
+	int poll_mask;
+	struct hvc_struct *hp;
+
+	set_freezable();
+	do {
+		poll_mask = 0;
+		hvc_kicked = 0;
+		try_to_freeze();
+		wmb();
+		if (!cpus_are_in_xmon()) {
+			spin_lock(&hvc_structs_lock);
+			list_for_each_entry(hp, &hvc_structs, next) {
+				poll_mask |= hvc_poll(hp);
+			}
+			spin_unlock(&hvc_structs_lock);
+		} else
+			poll_mask |= HVC_POLL_READ;
+		if (hvc_kicked)
+			continue;
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (!hvc_kicked) {
+			if (poll_mask == 0)
+				schedule();
+			else {
+				if (timeout < MAX_TIMEOUT)
+					timeout += (timeout >> 6) + 1;
+
+				msleep_interruptible(timeout);
+			}
+		}
+		__set_current_state(TASK_RUNNING);
+	} while (!kthread_should_stop());
+
+	return 0;
+}
+
+static const struct tty_operations hvc_ops = {
+	.open = hvc_open,
+	.close = hvc_close,
+	.write = hvc_write,
+	.hangup = hvc_hangup,
+	.unthrottle = hvc_unthrottle,
+	.write_room = hvc_write_room,
+	.chars_in_buffer = hvc_chars_in_buffer,
+};
+
+struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
+			     const struct hv_ops *ops,
+			     int outbuf_size)
+{
+	struct hvc_struct *hp;
+	int i;
+
+	/* We wait until a driver actually comes along */
+	if (!hvc_driver) {
+		int err = hvc_init();
+		if (err)
+			return ERR_PTR(err);
+	}
+
+	hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
+			GFP_KERNEL);
+	if (!hp)
+		return ERR_PTR(-ENOMEM);
+
+	hp->vtermno = vtermno;
+	hp->data = data;
+	hp->ops = ops;
+	hp->outbuf_size = outbuf_size;
+	hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
+
+	kref_init(&hp->kref);
+
+	INIT_WORK(&hp->tty_resize, hvc_set_winsz);
+	spin_lock_init(&hp->lock);
+	spin_lock(&hvc_structs_lock);
+
+	/*
+	 * find index to use:
+	 * see if this vterm id matches one registered for console.
+	 */
+	for (i=0; i < MAX_NR_HVC_CONSOLES; i++)
+		if (vtermnos[i] == hp->vtermno &&
+		    cons_ops[i] == hp->ops)
+			break;
+
+	/* no matching slot, just use a counter */
+	if (i >= MAX_NR_HVC_CONSOLES)
+		i = ++last_hvc;
+
+	hp->index = i;
+
+	list_add_tail(&(hp->next), &hvc_structs);
+	spin_unlock(&hvc_structs_lock);
+
+	return hp;
+}
+EXPORT_SYMBOL_GPL(hvc_alloc);
+
+int hvc_remove(struct hvc_struct *hp)
+{
+	unsigned long flags;
+	struct tty_struct *tty;
+
+	spin_lock_irqsave(&hp->lock, flags);
+	tty = tty_kref_get(hp->tty);
+
+	if (hp->index < MAX_NR_HVC_CONSOLES)
+		vtermnos[hp->index] = -1;
+
+	/* Don't whack hp->irq because tty_hangup() will need to free the irq. */
+
+	spin_unlock_irqrestore(&hp->lock, flags);
+
+	/*
+	 * We 'put' the instance that was grabbed when the kref instance
+	 * was initialized using kref_init().  Let the last holder of this
+	 * kref cause it to be removed, which will probably be the tty_vhangup
+	 * below.
+	 */
+	kref_put(&hp->kref, destroy_hvc_struct);
+
+	/*
+	 * This function call will auto chain call hvc_hangup.
+	 */
+	if (tty) {
+		tty_vhangup(tty);
+		tty_kref_put(tty);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hvc_remove);
+
+/* Driver initialization: called as soon as someone uses hvc_alloc(). */
+static int hvc_init(void)
+{
+	struct tty_driver *drv;
+	int err;
+
+	/* We need more than hvc_count adapters due to hotplug additions. */
+	drv = alloc_tty_driver(HVC_ALLOC_TTY_ADAPTERS);
+	if (!drv) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	drv->owner = THIS_MODULE;
+	drv->driver_name = "hvc";
+	drv->name = "hvc";
+	drv->major = HVC_MAJOR;
+	drv->minor_start = HVC_MINOR;
+	drv->type = TTY_DRIVER_TYPE_SYSTEM;
+	drv->init_termios = tty_std_termios;
+	drv->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_RESET_TERMIOS;
+	tty_set_operations(drv, &hvc_ops);
+
+	/* Always start the kthread because there can be hotplug vty adapters
+	 * added later. */
+	hvc_task = kthread_run(khvcd, NULL, "khvcd");
+	if (IS_ERR(hvc_task)) {
+		printk(KERN_ERR "Couldn't create kthread for console.\n");
+		err = PTR_ERR(hvc_task);
+		goto put_tty;
+	}
+
+	err = tty_register_driver(drv);
+	if (err) {
+		printk(KERN_ERR "Couldn't register hvc console driver\n");
+		goto stop_thread;
+	}
+
+	/*
+	 * Make sure tty is fully registered before allowing it to be
+	 * found by hvc_console_device.
+	 */
+	smp_mb();
+	hvc_driver = drv;
+	return 0;
+
+stop_thread:
+	kthread_stop(hvc_task);
+	hvc_task = NULL;
+put_tty:
+	put_tty_driver(drv);
+out:
+	return err;
+}
+
+/* This isn't particularly necessary due to this being a console driver
+ * but it is nice to be thorough.
+ */
+static void __exit hvc_exit(void)
+{
+	if (hvc_driver) {
+		kthread_stop(hvc_task);
+
+		tty_unregister_driver(hvc_driver);
+		/* return tty_struct instances allocated in hvc_init(). */
+		put_tty_driver(hvc_driver);
+		unregister_console(&hvc_console);
+	}
+}
+module_exit(hvc_exit);