text: /*
   * Copyright (C) 2004 Hollis Blanchard <hollisb@us.ibm.com>, IBM
   *
   * 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
   */
  
  /* Host Virtual Serial Interface (HVSI) is a protocol between the hosted OS
   * and the service processor on IBM pSeries servers. On these servers, there
   * are no serial ports under the OS's control, and sometimes there is no other
   * console available either. However, the service processor has two standard
   * serial ports, so this over-complicated protocol allows the OS to control
   * those ports by proxy.
   *
   * Besides data, the procotol supports the reading/writing of the serial
   * port's DTR line, and the reading of the CD line. This is to allow the OS to
   * control a modem attached to the service processor's serial port. Note that
   * the OS cannot change the speed of the port through this protocol.
   */
  
  #undef DEBUG
  
  #include <linux/console.h>
  #include <linux/ctype.h>
  #include <linux/delay.h>
  #include <linux/init.h>
  #include <linux/interrupt.h>
  #include <linux/module.h>
  #include <linux/major.h>
  #include <linux/kernel.h>
  #include <linux/spinlock.h>
  #include <linux/sysrq.h>
  #include <linux/tty.h>
  #include <linux/tty_flip.h>
  #include <asm/hvcall.h>
  #include <asm/hvconsole.h>
  #include <asm/prom.h>
  #include <asm/uaccess.h>
  #include <asm/vio.h>
  #include <asm/param.h>
  #include <asm/hvsi.h>
  
  #define HVSI_MAJOR	229
  #define HVSI_MINOR	128
  #define MAX_NR_HVSI_CONSOLES 4
  
  #define HVSI_TIMEOUT (5*HZ)
  #define HVSI_VERSION 1
  #define HVSI_MAX_PACKET 256
  #define HVSI_MAX_READ 16
  #define HVSI_MAX_OUTGOING_DATA 12
  #define N_OUTBUF 12
  
  /*
   * we pass data via two 8-byte registers, so we would like our char arrays
   * properly aligned for those loads.
   */
  #define __ALIGNED__	__attribute__((__aligned__(sizeof(long))))
  
  struct hvsi_struct {
  	struct delayed_work writer;
  	struct work_struct handshaker;
  	wait_queue_head_t emptyq; /* woken when outbuf is emptied */
  	wait_queue_head_t stateq; /* woken when HVSI state changes */
  	spinlock_t lock;
  	int index;
  	struct tty_struct *tty;
  	int count;
  	uint8_t throttle_buf[128];
  	uint8_t outbuf[N_OUTBUF]; /* to implement write_room and chars_in_buffer */
  	/* inbuf is for packet reassembly. leave a little room for leftovers. */
  	uint8_t inbuf[HVSI_MAX_PACKET + HVSI_MAX_READ];
  	uint8_t *inbuf_end;
  	int n_throttle;
  	int n_outbuf;
  	uint32_t vtermno;
  	uint32_t virq;
  	atomic_t seqno; /* HVSI packet sequence number */
  	uint16_t mctrl;
  	uint8_t state;  /* HVSI protocol state */
  	uint8_t flags;
  #ifdef CONFIG_MAGIC_SYSRQ
  	uint8_t sysrq;
  #endif /* CONFIG_MAGIC_SYSRQ */
  };
  static struct hvsi_struct hvsi_ports[MAX_NR_HVSI_CONSOLES];
  
  static struct tty_driver *hvsi_driver;
  static int hvsi_count;
  static int (*hvsi_wait)(struct hvsi_struct *hp, int state);
  
  enum HVSI_PROTOCOL_STATE {
  	HVSI_CLOSED,
  	HVSI_WAIT_FOR_VER_RESPONSE,
  	HVSI_WAIT_FOR_VER_QUERY,
  	HVSI_OPEN,
  	HVSI_WAIT_FOR_MCTRL_RESPONSE,
  	HVSI_FSP_DIED,
  };
  #define HVSI_CONSOLE 0x1
  
  static inline int is_console(struct hvsi_struct *hp)
  {
  	return hp->flags & HVSI_CONSOLE;
  }
  
  static inline int is_open(struct hvsi_struct *hp)
  {
  	/* if we're waiting for an mctrl then we're already open */
  	return (hp->state == HVSI_OPEN)
  			|| (hp->state == HVSI_WAIT_FOR_MCTRL_RESPONSE);
  }
  
  static inline void print_state(struct hvsi_struct *hp)
  {
  #ifdef DEBUG
  	static const char *state_names[] = {
  		"HVSI_CLOSED",
  		"HVSI_WAIT_FOR_VER_RESPONSE",
  		"HVSI_WAIT_FOR_VER_QUERY",
  		"HVSI_OPEN",
  		"HVSI_WAIT_FOR_MCTRL_RESPONSE",
  		"HVSI_FSP_DIED",
  	};
  	const char *name = (hp->state < ARRAY_SIZE(state_names))
  		? state_names[hp->state] : "UNKNOWN";
  
  	pr_debug("hvsi%i: state = %s\n", hp->index, name);
  #endif /* DEBUG */
  }
  
  static inline void __set_state(struct hvsi_struct *hp, int state)
  {
  	hp->state = state;
  	print_state(hp);
  	wake_up_all(&hp->stateq);
  }
  
  static inline void set_state(struct hvsi_struct *hp, int state)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&hp->lock, flags);
  	__set_state(hp, state);
  	spin_unlock_irqrestore(&hp->lock, flags);
  }
  
  static inline int len_packet(const uint8_t *packet)
  {
  	return (int)((struct hvsi_header *)packet)->len;
  }
  
  static inline int is_header(const uint8_t *packet)
  {
  	struct hvsi_header *header = (struct hvsi_header *)packet;
  	return header->type >= VS_QUERY_RESPONSE_PACKET_HEADER;
  }
  
  static inline int got_packet(const struct hvsi_struct *hp, uint8_t *packet)
  {
  	if (hp->inbuf_end < packet + sizeof(struct hvsi_header))
  		return 0; /* don't even have the packet header */
  
  	if (hp->inbuf_end < (packet + len_packet(packet)))
  		return 0; /* don't have the rest of the packet */
  
  	return 1;
  }
  
  /* shift remaining bytes in packetbuf down */
  static void compact_inbuf(struct hvsi_struct *hp, uint8_t *read_to)
  {
  	int remaining = (int)(hp->inbuf_end - read_to);
  
  	pr_debug("%s: %i chars remain\n", __func__, remaining);
  
  	if (read_to != hp->inbuf)
  		memmove(hp->inbuf, read_to, remaining);
  
  	hp->inbuf_end = hp->inbuf + remaining;
  }
  
  #ifdef DEBUG
  #define dbg_dump_packet(packet) dump_packet(packet)
  #define dbg_dump_hex(data, len) dump_hex(data, len)
  #else
  #define dbg_dump_packet(packet) do { } while (0)
  #define dbg_dump_hex(data, len) do { } while (0)
  #endif
  
  static void dump_hex(const uint8_t *data, int len)
  {
  	int i;
  
  	printk("    ");
  	for (i=0; i < len; i++)
  		printk("%.2x", data[i]);
  
  	printk("\n    ");
  	for (i=0; i < len; i++) {
  		if (isprint(data[i]))
  			printk("%c", data[i]);
  		else
  			printk(".");
  	}
  	printk("\n");
  }
  
  static void dump_packet(uint8_t *packet)
  {
  	struct hvsi_header *header = (struct hvsi_header *)packet;
  
  	printk("type 0x%x, len %i, seqno %i:\n", header->type, header->len,
  			header->seqno);
  
  	dump_hex(packet, header->len);
  }
  
  static int hvsi_read(struct hvsi_struct *hp, char *buf, int count)
  {
  	unsigned long got;
  
  	got = hvc_get_chars(hp->vtermno, buf, count);
  
  	return got;
  }
  
  static void hvsi_recv_control(struct hvsi_struct *hp, uint8_t *packet,
  	struct tty_struct **to_hangup, struct hvsi_struct **to_handshake)
  {
  	struct hvsi_control *header = (struct hvsi_control *)packet;
  
  	switch (header->verb) {
  		case VSV_MODEM_CTL_UPDATE:
  			if ((header->word & HVSI_TSCD) == 0) {
  				/* CD went away; no more connection */
  				pr_debug("hvsi%i: CD dropped\n", hp->index);
  				hp->mctrl &= TIOCM_CD;
  				/* If userland hasn't done an open(2) yet, hp->tty is NULL. */
  				if (hp->tty && !(hp->tty->flags & CLOCAL))
  					*to_hangup = hp->tty;
  			}
  			break;
  		case VSV_CLOSE_PROTOCOL:
  			pr_debug("hvsi%i: service processor came back\n", hp->index);
  			if (hp->state != HVSI_CLOSED) {
  				*to_handshake = hp;
  			}
  			break;
  		default:
  			printk(KERN_WARNING "hvsi%i: unknown HVSI control packet: ",
  				hp->index);
  			dump_packet(packet);
  			break;
  	}
  }
  
  static void hvsi_recv_response(struct hvsi_struct *hp, uint8_t *packet)
  {
  	struct hvsi_query_response *resp = (struct hvsi_query_response *)packet;
  
  	switch (hp->state) {
  		case HVSI_WAIT_FOR_VER_RESPONSE:
  			__set_state(hp, HVSI_WAIT_FOR_VER_QUERY);
  			break;
  		case HVSI_WAIT_FOR_MCTRL_RESPONSE:
  			hp->mctrl = 0;
  			if (resp->u.mctrl_word & HVSI_TSDTR)
  				hp->mctrl |= TIOCM_DTR;
  			if (resp->u.mctrl_word & HVSI_TSCD)
  				hp->mctrl |= TIOCM_CD;
  			__set_state(hp, HVSI_OPEN);
  			break;
  		default:
  			printk(KERN_ERR "hvsi%i: unexpected query response: ", hp->index);
  			dump_packet(packet);
  			break;
  	}
  }
  
  /* respond to service processor's version query */
  static int hvsi_version_respond(struct hvsi_struct *hp, uint16_t query_seqno)
  {
  	struct hvsi_query_response packet __ALIGNED__;
  	int wrote;
  
  	packet.hdr.type = VS_QUERY_RESPONSE_PACKET_HEADER;
  	packet.hdr.len = sizeof(struct hvsi_query_response);
  	packet.hdr.seqno = atomic_inc_return(&hp->seqno);
  	packet.verb = VSV_SEND_VERSION_NUMBER;
  	packet.u.version = HVSI_VERSION;
  	packet.query_seqno = query_seqno+1;
  
  	pr_debug("%s: sending %i bytes\n", __func__, packet.hdr.len);
  	dbg_dump_hex((uint8_t*)&packet, packet.hdr.len);
  
  	wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
  	if (wrote != packet.hdr.len) {
  		printk(KERN_ERR "hvsi%i: couldn't send query response!\n",
  			hp->index);
  		return -EIO;
  	}
  
  	return 0;
  }
  
  static void hvsi_recv_query(struct hvsi_struct *hp, uint8_t *packet)
  {
  	struct hvsi_query *query = (struct hvsi_query *)packet;
  
  	switch (hp->state) {
  		case HVSI_WAIT_FOR_VER_QUERY:
  			hvsi_version_respond(hp, query->hdr.seqno);
  			__set_state(hp, HVSI_OPEN);
  			break;
  		default:
  			printk(KERN_ERR "hvsi%i: unexpected query: ", hp->index);
  			dump_packet(packet);
  			break;
  	}
  }
  
  static void hvsi_insert_chars(struct hvsi_struct *hp, const char *buf, int len)
  {
  	int i;
  
  	for (i=0; i < len; i++) {
  		char c = buf[i];
  #ifdef CONFIG_MAGIC_SYSRQ
  		if (c == '\0') {
  			hp->sysrq = 1;
  			continue;
  		} else if (hp->sysrq) {
  			handle_sysrq(c);
  			hp->sysrq = 0;
  			continue;
  		}
  #endif /* CONFIG_MAGIC_SYSRQ */
  		tty_insert_flip_char(hp->tty, c, 0);
  	}
  }
  
  /*
   * We could get 252 bytes of data at once here. But the tty layer only
   * throttles us at TTY_THRESHOLD_THROTTLE (128) bytes, so we could overflow
   * it. Accordingly we won't send more than 128 bytes at a time to the flip
   * buffer, which will give the tty buffer a chance to throttle us. Should the
   * value of TTY_THRESHOLD_THROTTLE change in n_tty.c, this code should be
   * revisited.
   */
  #define TTY_THRESHOLD_THROTTLE 128
  static struct tty_struct *hvsi_recv_data(struct hvsi_struct *hp,
  		const uint8_t *packet)
  {
  	const struct hvsi_header *header = (const struct hvsi_header *)packet;
  	const uint8_t *data = packet + sizeof(struct hvsi_header);
  	int datalen = header->len - sizeof(struct hvsi_header);
  	int overflow = datalen - TTY_THRESHOLD_THROTTLE;
  
  	pr_debug("queueing %i chars '%.*s'\n", datalen, datalen, data);
  
  	if (datalen == 0)
  		return NULL;
  
  	if (overflow > 0) {
  		pr_debug("%s: got >TTY_THRESHOLD_THROTTLE bytes\n", __func__);
  		datalen = TTY_THRESHOLD_THROTTLE;
  	}
  
  	hvsi_insert_chars(hp, data, datalen);
  
  	if (overflow > 0) {
  		/*
  		 * we still have more data to deliver, so we need to save off the
  		 * overflow and send it later
  		 */
  		pr_debug("%s: deferring overflow\n", __func__);
  		memcpy(hp->throttle_buf, data + TTY_THRESHOLD_THROTTLE, overflow);
  		hp->n_throttle = overflow;
  	}
  
  	return hp->tty;
  }
  
  /*
   * Returns true/false indicating data successfully read from hypervisor.
   * Used both to get packets for tty connections and to advance the state
   * machine during console handshaking (in which case tty = NULL and we ignore
   * incoming data).
   */
  static int hvsi_load_chunk(struct hvsi_struct *hp, struct tty_struct **flip,
  		struct tty_struct **hangup, struct hvsi_struct **handshake)
  {
  	uint8_t *packet = hp->inbuf;
  	int chunklen;
  
  	*flip = NULL;
  	*hangup = NULL;
  	*handshake = NULL;
  
  	chunklen = hvsi_read(hp, hp->inbuf_end, HVSI_MAX_READ);
  	if (chunklen == 0) {
  		pr_debug("%s: 0-length read\n", __func__);
  		return 0;
  	}
  
  	pr_debug("%s: got %i bytes\n", __func__, chunklen);
  	dbg_dump_hex(hp->inbuf_end, chunklen);
  
  	hp->inbuf_end += chunklen;
  
  	/* handle all completed packets */
  	while ((packet < hp->inbuf_end) && got_packet(hp, packet)) {
  		struct hvsi_header *header = (struct hvsi_header *)packet;
  
  		if (!is_header(packet)) {
  			printk(KERN_ERR "hvsi%i: got malformed packet\n", hp->index);
  			/* skip bytes until we find a header or run out of data */
  			while ((packet < hp->inbuf_end) && (!is_header(packet)))
  				packet++;
  			continue;
  		}
  
  		pr_debug("%s: handling %i-byte packet\n", __func__,
  				len_packet(packet));
  		dbg_dump_packet(packet);
  
  		switch (header->type) {
  			case VS_DATA_PACKET_HEADER:
  				if (!is_open(hp))
  					break;
  				if (hp->tty == NULL)
  					break; /* no tty buffer to put data in */
  				*flip = hvsi_recv_data(hp, packet);
  				break;
  			case VS_CONTROL_PACKET_HEADER:
  				hvsi_recv_control(hp, packet, hangup, handshake);
  				break;
  			case VS_QUERY_RESPONSE_PACKET_HEADER:
  				hvsi_recv_response(hp, packet);
  				break;
  			case VS_QUERY_PACKET_HEADER:
  				hvsi_recv_query(hp, packet);
  				break;
  			default:
  				printk(KERN_ERR "hvsi%i: unknown HVSI packet type 0x%x\n",
  						hp->index, header->type);
  				dump_packet(packet);
  				break;
  		}
  
  		packet += len_packet(packet);
  
  		if (*hangup || *handshake) {
  			pr_debug("%s: hangup or handshake\n", __func__);
  			/*
  			 * we need to send the hangup now before receiving any more data.
  			 * If we get "data, hangup, data", we can't deliver the second
  			 * data before the hangup.
  			 */
  			break;
  		}
  	}
  
  	compact_inbuf(hp, packet);
  
  	return 1;
  }
  
  static void hvsi_send_overflow(struct hvsi_struct *hp)
  {
  	pr_debug("%s: delivering %i bytes overflow\n", __func__,
  			hp->n_throttle);
  
  	hvsi_insert_chars(hp, hp->throttle_buf, hp->n_throttle);
  	hp->n_throttle = 0;
  }
  
  /*
   * must get all pending data because we only get an irq on empty->non-empty
   * transition
   */
  static irqreturn_t hvsi_interrupt(int irq, void *arg)
  {
  	struct hvsi_struct *hp = (struct hvsi_struct *)arg;
  	struct tty_struct *flip;
  	struct tty_struct *hangup;
  	struct hvsi_struct *handshake;
  	unsigned long flags;
  	int again = 1;
  
  	pr_debug("%s\n", __func__);
  
  	while (again) {
  		spin_lock_irqsave(&hp->lock, flags);
  		again = hvsi_load_chunk(hp, &flip, &hangup, &handshake);
  		spin_unlock_irqrestore(&hp->lock, flags);
  
  		/*
  		 * we have to call tty_flip_buffer_push() and tty_hangup() outside our
  		 * spinlock. But we also have to keep going until we've read all the
  		 * available data.
  		 */
  
  		if (flip) {
  			/* there was data put in the tty flip buffer */
  			tty_flip_buffer_push(flip);
  			flip = NULL;
  		}
  
  		if (hangup) {
  			tty_hangup(hangup);
  		}
  
  		if (handshake) {
  			pr_debug("hvsi%i: attempting re-handshake\n", handshake->index);
  			schedule_work(&handshake->handshaker);
  		}
  	}
  
  	spin_lock_irqsave(&hp->lock, flags);
  	if (hp->tty && hp->n_throttle
  			&& (!test_bit(TTY_THROTTLED, &hp->tty->flags))) {
  		/* we weren't hung up and we weren't throttled, so we can deliver the
  		 * rest now */
  		flip = hp->tty;
  		hvsi_send_overflow(hp);
  	}
  	spin_unlock_irqrestore(&hp->lock, flags);
  
  	if (flip) {
  		tty_flip_buffer_push(flip);
  	}
  
  	return IRQ_HANDLED;
  }
  
  /* for boot console, before the irq handler is running */
  static int __init poll_for_state(struct hvsi_struct *hp, int state)
  {
  	unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;
  
  	for (;;) {
  		hvsi_interrupt(hp->virq, (void *)hp); /* get pending data */
  
  		if (hp->state == state)
  			return 0;
  
  		mdelay(5);
  		if (time_after(jiffies, end_jiffies))
  			return -EIO;
  	}
  }
  
  /* wait for irq handler to change our state */
  static int wait_for_state(struct hvsi_struct *hp, int state)
  {
  	int ret = 0;
  
  	if (!wait_event_timeout(hp->stateq, (hp->state == state), HVSI_TIMEOUT))
  		ret = -EIO;
  
  	return ret;
  }
  
  static int hvsi_query(struct hvsi_struct *hp, uint16_t verb)
  {
  	struct hvsi_query packet __ALIGNED__;
  	int wrote;
  
  	packet.hdr.type = VS_QUERY_PACKET_HEADER;
  	packet.hdr.len = sizeof(struct hvsi_query);
  	packet.hdr.seqno = atomic_inc_return(&hp->seqno);
  	packet.verb = verb;
  
  	pr_debug("%s: sending %i bytes\n", __func__, packet.hdr.len);
  	dbg_dump_hex((uint8_t*)&packet, packet.hdr.len);
  
  	wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
  	if (wrote != packet.hdr.len) {
  		printk(KERN_ERR "hvsi%i: couldn't send query (%i)!\n", hp->index,
  			wrote);
  		return -EIO;
  	}
  
  	return 0;
  }
  
  static int hvsi_get_mctrl(struct hvsi_struct *hp)
  {
  	int ret;
  
  	set_state(hp, HVSI_WAIT_FOR_MCTRL_RESPONSE);
  	hvsi_query(hp, VSV_SEND_MODEM_CTL_STATUS);
  
  	ret = hvsi_wait(hp, HVSI_OPEN);
  	if (ret < 0) {
  		printk(KERN_ERR "hvsi%i: didn't get modem flags\n", hp->index);
  		set_state(hp, HVSI_OPEN);
  		return ret;
  	}
  
  	pr_debug("%s: mctrl 0x%x\n", __func__, hp->mctrl);
  
  	return 0;
  }
  
  /* note that we can only set DTR */
  static int hvsi_set_mctrl(struct hvsi_struct *hp, uint16_t mctrl)
  {
  	struct hvsi_control packet __ALIGNED__;
  	int wrote;
  
  	packet.hdr.type = VS_CONTROL_PACKET_HEADER,
  	packet.hdr.seqno = atomic_inc_return(&hp->seqno);
  	packet.hdr.len = sizeof(struct hvsi_control);
  	packet.verb = VSV_SET_MODEM_CTL;
  	packet.mask = HVSI_TSDTR;
  
  	if (mctrl & TIOCM_DTR)
  		packet.word = HVSI_TSDTR;
  
  	pr_debug("%s: sending %i bytes\n", __func__, packet.hdr.len);
  	dbg_dump_hex((uint8_t*)&packet, packet.hdr.len);
  
  	wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
  	if (wrote != packet.hdr.len) {
  		printk(KERN_ERR "hvsi%i: couldn't set DTR!\n", hp->index);
  		return -EIO;
  	}
  
  	return 0;
  }
  
  static void hvsi_drain_input(struct hvsi_struct *hp)
  {
  	uint8_t buf[HVSI_MAX_READ] __ALIGNED__;
  	unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;
  
  	while (time_before(end_jiffies, jiffies))
  		if (0 == hvsi_read(hp, buf, HVSI_MAX_READ))
  			break;
  }
  
  static int hvsi_handshake(struct hvsi_struct *hp)
  {
  	int ret;
  
  	/*
  	 * We could have a CLOSE or other data waiting for us before we even try
  	 * to open; try to throw it all away so we don't get confused. (CLOSE
  	 * is the first message sent up the pipe when the FSP comes online. We
  	 * need to distinguish between "it came up a while ago and we're the first
  	 * user" and "it was just reset before it saw our handshake packet".)
  	 */
  	hvsi_drain_input(hp);
  
  	set_state(hp, HVSI_WAIT_FOR_VER_RESPONSE);
  	ret = hvsi_query(hp, VSV_SEND_VERSION_NUMBER);
  	if (ret < 0) {
  		printk(KERN_ERR "hvsi%i: couldn't send version query\n", hp->index);
  		return ret;
  	}
  
  	ret = hvsi_wait(hp, HVSI_OPEN);
  	if (ret < 0)
  		return ret;
  
  	return 0;
  }
  
  static void hvsi_handshaker(struct work_struct *work)
  {
  	struct hvsi_struct *hp =
  		container_of(work, struct hvsi_struct, handshaker);
  
  	if (hvsi_handshake(hp) >= 0)
  		return;
  
  	printk(KERN_ERR "hvsi%i: re-handshaking failed\n", hp->index);
  	if (is_console(hp)) {
  		/*
  		 * ttys will re-attempt the handshake via hvsi_open, but
  		 * the console will not.
  		 */
  		printk(KERN_ERR "hvsi%i: lost console!\n", hp->index);
  	}
  }
  
  static int hvsi_put_chars(struct hvsi_struct *hp, const char *buf, int count)
  {
  	struct hvsi_data packet __ALIGNED__;
  	int ret;
  
  	BUG_ON(count > HVSI_MAX_OUTGOING_DATA);
  
  	packet.hdr.type = VS_DATA_PACKET_HEADER;
  	packet.hdr.seqno = atomic_inc_return(&hp->seqno);
  	packet.hdr.len = count + sizeof(struct hvsi_header);
  	memcpy(&packet.data, buf, count);
  
  	ret = hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
  	if (ret == packet.hdr.len) {
  		/* return the number of chars written, not the packet length */
  		return count;
  	}
  	return ret; /* return any errors */
  }
  
  static void hvsi_close_protocol(struct hvsi_struct *hp)
  {
  	struct hvsi_control packet __ALIGNED__;
  
  	packet.hdr.type = VS_CONTROL_PACKET_HEADER;
  	packet.hdr.seqno = atomic_inc_return(&hp->seqno);
  	packet.hdr.len = 6;
  	packet.verb = VSV_CLOSE_PROTOCOL;
  
  	pr_debug("%s: sending %i bytes\n", __func__, packet.hdr.len);
  	dbg_dump_hex((uint8_t*)&packet, packet.hdr.len);
  
  	hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
  }
  
  static int hvsi_open(struct tty_struct *tty, struct file *filp)
  {
  	struct hvsi_struct *hp;
  	unsigned long flags;
  	int line = tty->index;
  	int ret;
  
  	pr_debug("%s\n", __func__);
  
  	if (line < 0 || line >= hvsi_count)
  		return -ENODEV;
  	hp = &hvsi_ports[line];
  
  	tty->driver_data = hp;
  
  	mb();
  	if (hp->state == HVSI_FSP_DIED)
  		return -EIO;
  
  	spin_lock_irqsave(&hp->lock, flags);
  	hp->tty = tty;
  	hp->count++;
  	atomic_set(&hp->seqno, 0);
  	h_vio_signal(hp->vtermno, VIO_IRQ_ENABLE);
  	spin_unlock_irqrestore(&hp->lock, flags);
  
  	if (is_console(hp))
  		return 0; /* this has already been handshaked as the console */
  
  	ret = hvsi_handshake(hp);
  	if (ret < 0) {
  		printk(KERN_ERR "%s: HVSI handshaking failed\n", tty->name);
  		return ret;
  	}
  
  	ret = hvsi_get_mctrl(hp);
  	if (ret < 0) {
  		printk(KERN_ERR "%s: couldn't get initial modem flags\n", tty->name);
  		return ret;
  	}
  
  	ret = hvsi_set_mctrl(hp, hp->mctrl | TIOCM_DTR);
  	if (ret < 0) {
  		printk(KERN_ERR "%s: couldn't set DTR\n", tty->name);
  		return ret;
  	}
  
  	return 0;
  }
  
  /* wait for hvsi_write_worker to empty hp->outbuf */
  static void hvsi_flush_output(struct hvsi_struct *hp)
  {
  	wait_event_timeout(hp->emptyq, (hp->n_outbuf <= 0), HVSI_TIMEOUT);
  
  	/* 'writer' could still be pending if it didn't see n_outbuf = 0 yet */
  	cancel_delayed_work_sync(&hp->writer);
  	flush_work_sync(&hp->handshaker);
  
  	/*
  	 * it's also possible that our timeout expired and hvsi_write_worker
  	 * didn't manage to push outbuf. poof.
  	 */
  	hp->n_outbuf = 0;
  }
  
  static void hvsi_close(struct tty_struct *tty, struct file *filp)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  	unsigned long flags;
  
  	pr_debug("%s\n", __func__);
  
  	if (tty_hung_up_p(filp))
  		return;
  
  	spin_lock_irqsave(&hp->lock, flags);
  
  	if (--hp->count == 0) {
  		hp->tty = NULL;
  		hp->inbuf_end = hp->inbuf; /* discard remaining partial packets */
  
  		/* only close down connection if it is not the console */
  		if (!is_console(hp)) {
  			h_vio_signal(hp->vtermno, VIO_IRQ_DISABLE); /* no more irqs */
  			__set_state(hp, HVSI_CLOSED);
  			/*
  			 * any data delivered to the tty layer after this will be
  			 * discarded (except for XON/XOFF)
  			 */
  			tty->closing = 1;
  
  			spin_unlock_irqrestore(&hp->lock, flags);
  
  			/* let any existing irq handlers finish. no more will start. */
  			synchronize_irq(hp->virq);
  
  			/* hvsi_write_worker will re-schedule until outbuf is empty. */
  			hvsi_flush_output(hp);
  
  			/* tell FSP to stop sending data */
  			hvsi_close_protocol(hp);
  
  			/*
  			 * drain anything FSP is still in the middle of sending, and let
  			 * hvsi_handshake drain the rest on the next open.
  			 */
  			hvsi_drain_input(hp);
  
  			spin_lock_irqsave(&hp->lock, flags);
  		}
  	} else if (hp->count < 0)
  		printk(KERN_ERR "hvsi_close %lu: oops, count is %d\n",
  		       hp - hvsi_ports, hp->count);
  
  	spin_unlock_irqrestore(&hp->lock, flags);
  }
  
  static void hvsi_hangup(struct tty_struct *tty)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  	unsigned long flags;
  
  	pr_debug("%s\n", __func__);
  
  	spin_lock_irqsave(&hp->lock, flags);
  
  	hp->count = 0;
  	hp->n_outbuf = 0;
  	hp->tty = NULL;
  
  	spin_unlock_irqrestore(&hp->lock, flags);
  }
  
  /* called with hp->lock held */
  static void hvsi_push(struct hvsi_struct *hp)
  {
  	int n;
  
  	if (hp->n_outbuf <= 0)
  		return;
  
  	n = hvsi_put_chars(hp, hp->outbuf, hp->n_outbuf);
  	if (n > 0) {
  		/* success */
  		pr_debug("%s: wrote %i chars\n", __func__, n);
  		hp->n_outbuf = 0;
  	} else if (n == -EIO) {
  		__set_state(hp, HVSI_FSP_DIED);
  		printk(KERN_ERR "hvsi%i: service processor died\n", hp->index);
  	}
  }
  
  /* hvsi_write_worker will keep rescheduling itself until outbuf is empty */
  static void hvsi_write_worker(struct work_struct *work)
  {
  	struct hvsi_struct *hp =
  		container_of(work, struct hvsi_struct, writer.work);
  	unsigned long flags;
  #ifdef DEBUG
  	static long start_j = 0;
  
  	if (start_j == 0)
  		start_j = jiffies;
  #endif /* DEBUG */
  
  	spin_lock_irqsave(&hp->lock, flags);
  
  	pr_debug("%s: %i chars in buffer\n", __func__, hp->n_outbuf);
  
  	if (!is_open(hp)) {
  		/*
  		 * We could have a non-open connection if the service processor died
  		 * while we were busily scheduling ourselves. In that case, it could
  		 * be minutes before the service processor comes back, so only try
  		 * again once a second.
  		 */
  		schedule_delayed_work(&hp->writer, HZ);
  		goto out;
  	}
  
  	hvsi_push(hp);
  	if (hp->n_outbuf > 0)
  		schedule_delayed_work(&hp->writer, 10);
  	else {
  #ifdef DEBUG
  		pr_debug("%s: outbuf emptied after %li jiffies\n", __func__,
  				jiffies - start_j);
  		start_j = 0;
  #endif /* DEBUG */
  		wake_up_all(&hp->emptyq);
  		tty_wakeup(hp->tty);
  	}
  
  out:
  	spin_unlock_irqrestore(&hp->lock, flags);
  }
  
  static int hvsi_write_room(struct tty_struct *tty)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  
  	return N_OUTBUF - hp->n_outbuf;
  }
  
  static int hvsi_chars_in_buffer(struct tty_struct *tty)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  
  	return hp->n_outbuf;
  }
  
  static int hvsi_write(struct tty_struct *tty,
  		     const unsigned char *buf, int count)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  	const char *source = buf;
  	unsigned long flags;
  	int total = 0;
  	int origcount = count;
  
  	spin_lock_irqsave(&hp->lock, flags);
  
  	pr_debug("%s: %i chars in buffer\n", __func__, hp->n_outbuf);
  
  	if (!is_open(hp)) {
  		/* we're either closing or not yet open; don't accept data */
  		pr_debug("%s: not open\n", __func__);
  		goto out;
  	}
  
  	/*
  	 * when the hypervisor buffer (16K) fills, data will stay in hp->outbuf
  	 * and hvsi_write_worker will be scheduled. subsequent hvsi_write() calls
  	 * will see there is no room in outbuf and return.
  	 */
  	while ((count > 0) && (hvsi_write_room(hp->tty) > 0)) {
  		int chunksize = min(count, hvsi_write_room(hp->tty));
  
  		BUG_ON(hp->n_outbuf < 0);
  		memcpy(hp->outbuf + hp->n_outbuf, source, chunksize);
  		hp->n_outbuf += chunksize;
  
  		total += chunksize;
  		source += chunksize;
  		count -= chunksize;
  		hvsi_push(hp);
  	}
  
  	if (hp->n_outbuf > 0) {
  		/*
  		 * we weren't able to write it all to the hypervisor.
  		 * schedule another push attempt.
  		 */
  		schedule_delayed_work(&hp->writer, 10);
  	}
  
  out:
  	spin_unlock_irqrestore(&hp->lock, flags);
  
  	if (total != origcount)
  		pr_debug("%s: wanted %i, only wrote %i\n", __func__, origcount,
  			total);
  
  	return total;
  }
  
  /*
   * I have never seen throttle or unthrottle called, so this little throttle
   * buffering scheme may or may not work.
   */
  static void hvsi_throttle(struct tty_struct *tty)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  
  	pr_debug("%s\n", __func__);
  
  	h_vio_signal(hp->vtermno, VIO_IRQ_DISABLE);
  }
  
  static void hvsi_unthrottle(struct tty_struct *tty)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  	unsigned long flags;
  	int shouldflip = 0;
  
  	pr_debug("%s\n", __func__);
  
  	spin_lock_irqsave(&hp->lock, flags);
  	if (hp->n_throttle) {
  		hvsi_send_overflow(hp);
  		shouldflip = 1;
  	}
  	spin_unlock_irqrestore(&hp->lock, flags);
  
  	if (shouldflip)
  		tty_flip_buffer_push(hp->tty);
  
  	h_vio_signal(hp->vtermno, VIO_IRQ_ENABLE);
  }
  
  static int hvsi_tiocmget(struct tty_struct *tty)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  
  	hvsi_get_mctrl(hp);
  	return hp->mctrl;
  }
  
  static int hvsi_tiocmset(struct tty_struct *tty,
  				unsigned int set, unsigned int clear)
  {
  	struct hvsi_struct *hp = tty->driver_data;
  	unsigned long flags;
  	uint16_t new_mctrl;
  
  	/* we can only alter DTR */
  	clear &= TIOCM_DTR;
  	set &= TIOCM_DTR;
  
  	spin_lock_irqsave(&hp->lock, flags);
  
  	new_mctrl = (hp->mctrl & ~clear) | set;
  
  	if (hp->mctrl != new_mctrl) {
  		hvsi_set_mctrl(hp, new_mctrl);
  		hp->mctrl = new_mctrl;
  	}
  	spin_unlock_irqrestore(&hp->lock, flags);
  
  	return 0;
  }
  
  
  static const struct tty_operations hvsi_ops = {
  	.open = hvsi_open,
  	.close = hvsi_close,
  	.write = hvsi_write,
  	.hangup = hvsi_hangup,
  	.write_room = hvsi_write_room,
  	.chars_in_buffer = hvsi_chars_in_buffer,
  	.throttle = hvsi_throttle,
  	.unthrottle = hvsi_unthrottle,
  	.tiocmget = hvsi_tiocmget,
  	.tiocmset = hvsi_tiocmset,
  };
  
  static int __init hvsi_init(void)
  {
  	int i;
  
  	hvsi_driver = alloc_tty_driver(hvsi_count);
  	if (!hvsi_driver)
  		return -ENOMEM;
  
  	hvsi_driver->owner = THIS_MODULE;
  	hvsi_driver->driver_name = "hvsi";
  	hvsi_driver->name = "hvsi";
  	hvsi_driver->major = HVSI_MAJOR;
  	hvsi_driver->minor_start = HVSI_MINOR;
  	hvsi_driver->type = TTY_DRIVER_TYPE_SYSTEM;
  	hvsi_driver->init_termios = tty_std_termios;
  	hvsi_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL;
  	hvsi_driver->init_termios.c_ispeed = 9600;
  	hvsi_driver->init_termios.c_ospeed = 9600;
  	hvsi_driver->flags = TTY_DRIVER_REAL_RAW;
  	tty_set_operations(hvsi_driver, &hvsi_ops);
  
  	for (i=0; i < hvsi_count; i++) {
  		struct hvsi_struct *hp = &hvsi_ports[i];
  		int ret = 1;
  
  		ret = request_irq(hp->virq, hvsi_interrupt, 0, "hvsi", hp);
  		if (ret)
  			printk(KERN_ERR "HVSI: couldn't reserve irq 0x%x (error %i)\n",
  				hp->virq, ret);
  	}
  	hvsi_wait = wait_for_state; /* irqs active now */
  
  	if (tty_register_driver(hvsi_driver))
  		panic("Couldn't register hvsi console driver\n");
  
  	printk(KERN_DEBUG "HVSI: registered %i devices\n", hvsi_count);
  
  	return 0;
  }
  device_initcall(hvsi_init);
  
  /***** console (not tty) code: *****/
  
  static void hvsi_console_print(struct console *console, const char *buf,
  		unsigned int count)
  {
  	struct hvsi_struct *hp = &hvsi_ports[console->index];
  	char c[HVSI_MAX_OUTGOING_DATA] __ALIGNED__;
  	unsigned int i = 0, n = 0;
  	int ret, donecr = 0;
  
  	mb();
  	if (!is_open(hp))
  		return;
  
  	/*
  	 * ugh, we have to translate LF -> CRLF ourselves, in place.
  	 * copied from hvc_console.c:
  	 */
  	while (count > 0 || i > 0) {
  		if (count > 0 && i < sizeof(c)) {
  			if (buf[n] == '\n' && !donecr) {
  				c[i++] = '\r';
  				donecr = 1;
  			} else {
  				c[i++] = buf[n++];
  				donecr = 0;
  				--count;
  			}
  		} else {
  			ret = hvsi_put_chars(hp, c, i);
  			if (ret < 0)
  				i = 0;
  			i -= ret;
  		}
  	}
  }
  
  static struct tty_driver *hvsi_console_device(struct console *console,
  	int *index)
  {
  	*index = console->index;
  	return hvsi_driver;
  }
  
  static int __init hvsi_console_setup(struct console *console, char *options)
  {
  	struct hvsi_struct *hp;
  	int ret;
  
  	if (console->index < 0 || console->index >= hvsi_count)
  		return -1;
  	hp = &hvsi_ports[console->index];
  
  	/* give the FSP a chance to change the baud rate when we re-open */
  	hvsi_close_protocol(hp);
  
  	ret = hvsi_handshake(hp);
  	if (ret < 0)
  		return ret;
  
  	ret = hvsi_get_mctrl(hp);
  	if (ret < 0)
  		return ret;
  
  	ret = hvsi_set_mctrl(hp, hp->mctrl | TIOCM_DTR);
  	if (ret < 0)
  		return ret;
  
  	hp->flags |= HVSI_CONSOLE;
  
  	return 0;
  }
  
  static struct console hvsi_console = {
  	.name		= "hvsi",
  	.write		= hvsi_console_print,
  	.device		= hvsi_console_device,
  	.setup		= hvsi_console_setup,
  	.flags		= CON_PRINTBUFFER,
  	.index		= -1,
  };
  
  static int __init hvsi_console_init(void)
  {
  	struct device_node *vty;
  
  	hvsi_wait = poll_for_state; /* no irqs yet; must poll */
  
  	/* search device tree for vty nodes */
  	for (vty = of_find_compatible_node(NULL, "serial", "hvterm-protocol");
  			vty != NULL;
  			vty = of_find_compatible_node(vty, "serial", "hvterm-protocol")) {
  		struct hvsi_struct *hp;
  		const uint32_t *vtermno, *irq;
  
  		vtermno = of_get_property(vty, "reg", NULL);
  		irq = of_get_property(vty, "interrupts", NULL);
  		if (!vtermno || !irq)
  			continue;
  
  		if (hvsi_count >= MAX_NR_HVSI_CONSOLES) {
  			of_node_put(vty);
  			break;
  		}
  
  		hp = &hvsi_ports[hvsi_count];
  		INIT_DELAYED_WORK(&hp->writer, hvsi_write_worker);
  		INIT_WORK(&hp->handshaker, hvsi_handshaker);
  		init_waitqueue_head(&hp->emptyq);
  		init_waitqueue_head(&hp->stateq);
  		spin_lock_init(&hp->lock);
  		hp->index = hvsi_count;
  		hp->inbuf_end = hp->inbuf;
  		hp->state = HVSI_CLOSED;
  		hp->vtermno = *vtermno;
  		hp->virq = irq_create_mapping(NULL, irq[0]);
  		if (hp->virq == NO_IRQ) {
  			printk(KERN_ERR "%s: couldn't create irq mapping for 0x%x\n",
  				__func__, irq[0]);
  			continue;
  		}
  
  		hvsi_count++;
  	}
  
  	if (hvsi_count)
  		register_console(&hvsi_console);
  	return 0;
  }
  console_initcall(hvsi_console_init);
  