diff --git a/drivers/char/snsc.c b/drivers/char/snsc.c
new file mode 100644
index 0000000..ffb9143
--- /dev/null
+++ b/drivers/char/snsc.c
@@ -0,0 +1,448 @@
+/*
+ * SN Platform system controller communication support
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2004 Silicon Graphics, Inc. All rights reserved.
+ */
+
+/*
+ * System controller communication driver
+ *
+ * This driver allows a user process to communicate with the system
+ * controller (a.k.a. "IRouter") network in an SGI SN system.
+ */
+
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/device.h>
+#include <linux/poll.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <asm/sn/io.h>
+#include <asm/sn/sn_sal.h>
+#include <asm/sn/module.h>
+#include <asm/sn/geo.h>
+#include <asm/sn/nodepda.h>
+#include "snsc.h"
+
+#define SYSCTL_BASENAME	"snsc"
+
+#define SCDRV_BUFSZ	2048
+#define SCDRV_TIMEOUT	1000
+
+static irqreturn_t
+scdrv_interrupt(int irq, void *subch_data, struct pt_regs *regs)
+{
+	struct subch_data_s *sd = subch_data;
+	unsigned long flags;
+	int status;
+
+	spin_lock_irqsave(&sd->sd_rlock, flags);
+	spin_lock(&sd->sd_wlock);
+	status = ia64_sn_irtr_intr(sd->sd_nasid, sd->sd_subch);
+
+	if (status > 0) {
+		if (status & SAL_IROUTER_INTR_RECV) {
+			wake_up(&sd->sd_rq);
+		}
+		if (status & SAL_IROUTER_INTR_XMIT) {
+			ia64_sn_irtr_intr_disable
+			    (sd->sd_nasid, sd->sd_subch,
+			     SAL_IROUTER_INTR_XMIT);
+			wake_up(&sd->sd_wq);
+		}
+	}
+	spin_unlock(&sd->sd_wlock);
+	spin_unlock_irqrestore(&sd->sd_rlock, flags);
+	return IRQ_HANDLED;
+}
+
+/*
+ * scdrv_open
+ *
+ * Reserve a subchannel for system controller communication.
+ */
+
+static int
+scdrv_open(struct inode *inode, struct file *file)
+{
+	struct sysctl_data_s *scd;
+	struct subch_data_s *sd;
+	int rv;
+
+	/* look up device info for this device file */
+	scd = container_of(inode->i_cdev, struct sysctl_data_s, scd_cdev);
+
+	/* allocate memory for subchannel data */
+	sd = kmalloc(sizeof (struct subch_data_s), GFP_KERNEL);
+	if (sd == NULL) {
+		printk("%s: couldn't allocate subchannel data\n",
+		       __FUNCTION__);
+		return -ENOMEM;
+	}
+
+	/* initialize subch_data_s fields */
+	memset(sd, 0, sizeof (struct subch_data_s));
+	sd->sd_nasid = scd->scd_nasid;
+	sd->sd_subch = ia64_sn_irtr_open(scd->scd_nasid);
+
+	if (sd->sd_subch < 0) {
+		kfree(sd);
+		printk("%s: couldn't allocate subchannel\n", __FUNCTION__);
+		return -EBUSY;
+	}
+
+	spin_lock_init(&sd->sd_rlock);
+	spin_lock_init(&sd->sd_wlock);
+	init_waitqueue_head(&sd->sd_rq);
+	init_waitqueue_head(&sd->sd_wq);
+	sema_init(&sd->sd_rbs, 1);
+	sema_init(&sd->sd_wbs, 1);
+
+	file->private_data = sd;
+
+	/* hook this subchannel up to the system controller interrupt */
+	rv = request_irq(SGI_UART_VECTOR, scdrv_interrupt,
+			 SA_SHIRQ | SA_INTERRUPT,
+			 SYSCTL_BASENAME, sd);
+	if (rv) {
+		ia64_sn_irtr_close(sd->sd_nasid, sd->sd_subch);
+		kfree(sd);
+		printk("%s: irq request failed (%d)\n", __FUNCTION__, rv);
+		return -EBUSY;
+	}
+
+	return 0;
+}
+
+/*
+ * scdrv_release
+ *
+ * Release a previously-reserved subchannel.
+ */
+
+static int
+scdrv_release(struct inode *inode, struct file *file)
+{
+	struct subch_data_s *sd = (struct subch_data_s *) file->private_data;
+	int rv;
+
+	/* free the interrupt */
+	free_irq(SGI_UART_VECTOR, sd);
+
+	/* ask SAL to close the subchannel */
+	rv = ia64_sn_irtr_close(sd->sd_nasid, sd->sd_subch);
+
+	kfree(sd);
+	return rv;
+}
+
+/*
+ * scdrv_read
+ *
+ * Called to read bytes from the open IRouter pipe.
+ *
+ */
+
+static inline int
+read_status_check(struct subch_data_s *sd, int *len)
+{
+	return ia64_sn_irtr_recv(sd->sd_nasid, sd->sd_subch, sd->sd_rb, len);
+}
+
+static ssize_t
+scdrv_read(struct file *file, char __user *buf, size_t count, loff_t *f_pos)
+{
+	int status;
+	int len;
+	unsigned long flags;
+	struct subch_data_s *sd = (struct subch_data_s *) file->private_data;
+
+	/* try to get control of the read buffer */
+	if (down_trylock(&sd->sd_rbs)) {
+		/* somebody else has it now;
+		 * if we're non-blocking, then exit...
+		 */
+		if (file->f_flags & O_NONBLOCK) {
+			return -EAGAIN;
+		}
+		/* ...or if we want to block, then do so here */
+		if (down_interruptible(&sd->sd_rbs)) {
+			/* something went wrong with wait */
+			return -ERESTARTSYS;
+		}
+	}
+
+	/* anything to read? */
+	len = CHUNKSIZE;
+	spin_lock_irqsave(&sd->sd_rlock, flags);
+	status = read_status_check(sd, &len);
+
+	/* if not, and we're blocking I/O, loop */
+	while (status < 0) {
+		DECLARE_WAITQUEUE(wait, current);
+
+		if (file->f_flags & O_NONBLOCK) {
+			spin_unlock_irqrestore(&sd->sd_rlock, flags);
+			up(&sd->sd_rbs);
+			return -EAGAIN;
+		}
+
+		len = CHUNKSIZE;
+		set_current_state(TASK_INTERRUPTIBLE);
+		add_wait_queue(&sd->sd_rq, &wait);
+		spin_unlock_irqrestore(&sd->sd_rlock, flags);
+
+		schedule_timeout(SCDRV_TIMEOUT);
+
+		remove_wait_queue(&sd->sd_rq, &wait);
+		if (signal_pending(current)) {
+			/* wait was interrupted */
+			up(&sd->sd_rbs);
+			return -ERESTARTSYS;
+		}
+
+		spin_lock_irqsave(&sd->sd_rlock, flags);
+		status = read_status_check(sd, &len);
+	}
+	spin_unlock_irqrestore(&sd->sd_rlock, flags);
+
+	if (len > 0) {
+		/* we read something in the last read_status_check(); copy
+		 * it out to user space
+		 */
+		if (count < len) {
+			pr_debug("%s: only accepting %d of %d bytes\n",
+				 __FUNCTION__, (int) count, len);
+		}
+		len = min((int) count, len);
+		if (copy_to_user(buf, sd->sd_rb, len))
+			len = -EFAULT;
+	}
+
+	/* release the read buffer and wake anyone who might be
+	 * waiting for it
+	 */
+	up(&sd->sd_rbs);
+
+	/* return the number of characters read in */
+	return len;
+}
+
+/*
+ * scdrv_write
+ *
+ * Writes a chunk of an IRouter packet (or other system controller data)
+ * to the system controller.
+ *
+ */
+static inline int
+write_status_check(struct subch_data_s *sd, int count)
+{
+	return ia64_sn_irtr_send(sd->sd_nasid, sd->sd_subch, sd->sd_wb, count);
+}
+
+static ssize_t
+scdrv_write(struct file *file, const char __user *buf,
+	    size_t count, loff_t *f_pos)
+{
+	unsigned long flags;
+	int status;
+	struct subch_data_s *sd = (struct subch_data_s *) file->private_data;
+
+	/* try to get control of the write buffer */
+	if (down_trylock(&sd->sd_wbs)) {
+		/* somebody else has it now;
+		 * if we're non-blocking, then exit...
+		 */
+		if (file->f_flags & O_NONBLOCK) {
+			return -EAGAIN;
+		}
+		/* ...or if we want to block, then do so here */
+		if (down_interruptible(&sd->sd_wbs)) {
+			/* something went wrong with wait */
+			return -ERESTARTSYS;
+		}
+	}
+
+	count = min((int) count, CHUNKSIZE);
+	if (copy_from_user(sd->sd_wb, buf, count)) {
+		up(&sd->sd_wbs);
+		return -EFAULT;
+	}
+
+	/* try to send the buffer */
+	spin_lock_irqsave(&sd->sd_wlock, flags);
+	status = write_status_check(sd, count);
+
+	/* if we failed, and we want to block, then loop */
+	while (status <= 0) {
+		DECLARE_WAITQUEUE(wait, current);
+
+		if (file->f_flags & O_NONBLOCK) {
+			spin_unlock(&sd->sd_wlock);
+			up(&sd->sd_wbs);
+			return -EAGAIN;
+		}
+
+		set_current_state(TASK_INTERRUPTIBLE);
+		add_wait_queue(&sd->sd_wq, &wait);
+		spin_unlock_irqrestore(&sd->sd_wlock, flags);
+
+		schedule_timeout(SCDRV_TIMEOUT);
+
+		remove_wait_queue(&sd->sd_wq, &wait);
+		if (signal_pending(current)) {
+			/* wait was interrupted */
+			up(&sd->sd_wbs);
+			return -ERESTARTSYS;
+		}
+
+		spin_lock_irqsave(&sd->sd_wlock, flags);
+		status = write_status_check(sd, count);
+	}
+	spin_unlock_irqrestore(&sd->sd_wlock, flags);
+
+	/* release the write buffer and wake anyone who's waiting for it */
+	up(&sd->sd_wbs);
+
+	/* return the number of characters accepted (should be the complete
+	 * "chunk" as requested)
+	 */
+	if ((status >= 0) && (status < count)) {
+		pr_debug("Didn't accept the full chunk; %d of %d\n",
+			 status, (int) count);
+	}
+	return status;
+}
+
+static unsigned int
+scdrv_poll(struct file *file, struct poll_table_struct *wait)
+{
+	unsigned int mask = 0;
+	int status = 0;
+	struct subch_data_s *sd = (struct subch_data_s *) file->private_data;
+	unsigned long flags;
+
+	poll_wait(file, &sd->sd_rq, wait);
+	poll_wait(file, &sd->sd_wq, wait);
+
+	spin_lock_irqsave(&sd->sd_rlock, flags);
+	spin_lock(&sd->sd_wlock);
+	status = ia64_sn_irtr_intr(sd->sd_nasid, sd->sd_subch);
+	spin_unlock(&sd->sd_wlock);
+	spin_unlock_irqrestore(&sd->sd_rlock, flags);
+
+	if (status > 0) {
+		if (status & SAL_IROUTER_INTR_RECV) {
+			mask |= POLLIN | POLLRDNORM;
+		}
+		if (status & SAL_IROUTER_INTR_XMIT) {
+			mask |= POLLOUT | POLLWRNORM;
+		}
+	}
+
+	return mask;
+}
+
+static struct file_operations scdrv_fops = {
+	.owner =	THIS_MODULE,
+	.read =		scdrv_read,
+	.write =	scdrv_write,
+	.poll =		scdrv_poll,
+	.open =		scdrv_open,
+	.release =	scdrv_release,
+};
+
+/*
+ * scdrv_init
+ *
+ * Called at boot time to initialize the system controller communication
+ * facility.
+ */
+int __init
+scdrv_init(void)
+{
+	geoid_t geoid;
+	cnodeid_t cnode;
+	char devname[32];
+	char *devnamep;
+	struct sysctl_data_s *scd;
+	void *salbuf;
+	struct class_simple *snsc_class;
+	dev_t first_dev, dev;
+
+	if (alloc_chrdev_region(&first_dev, 0, numionodes,
+				SYSCTL_BASENAME) < 0) {
+		printk("%s: failed to register SN system controller device\n",
+		       __FUNCTION__);
+		return -ENODEV;
+	}
+	snsc_class = class_simple_create(THIS_MODULE, SYSCTL_BASENAME);
+
+	for (cnode = 0; cnode < numionodes; cnode++) {
+			geoid = cnodeid_get_geoid(cnode);
+			devnamep = devname;
+			format_module_id(devnamep, geo_module(geoid),
+					 MODULE_FORMAT_BRIEF);
+			devnamep = devname + strlen(devname);
+			sprintf(devnamep, "#%d", geo_slab(geoid));
+
+			/* allocate sysctl device data */
+			scd = kmalloc(sizeof (struct sysctl_data_s),
+				      GFP_KERNEL);
+			if (!scd) {
+				printk("%s: failed to allocate device info"
+				       "for %s/%s\n", __FUNCTION__,
+				       SYSCTL_BASENAME, devname);
+				continue;
+			}
+			memset(scd, 0, sizeof (struct sysctl_data_s));
+
+			/* initialize sysctl device data fields */
+			scd->scd_nasid = cnodeid_to_nasid(cnode);
+			if (!(salbuf = kmalloc(SCDRV_BUFSZ, GFP_KERNEL))) {
+				printk("%s: failed to allocate driver buffer"
+				       "(%s%s)\n", __FUNCTION__,
+				       SYSCTL_BASENAME, devname);
+				kfree(scd);
+				continue;
+			}
+
+			if (ia64_sn_irtr_init(scd->scd_nasid, salbuf,
+					      SCDRV_BUFSZ) < 0) {
+				printk
+				    ("%s: failed to initialize SAL for"
+				     " system controller communication"
+				     " (%s/%s): outdated PROM?\n",
+				     __FUNCTION__, SYSCTL_BASENAME, devname);
+				kfree(scd);
+				kfree(salbuf);
+				continue;
+			}
+
+			dev = first_dev + cnode;
+			cdev_init(&scd->scd_cdev, &scdrv_fops);
+			if (cdev_add(&scd->scd_cdev, dev, 1)) {
+				printk("%s: failed to register system"
+				       " controller device (%s%s)\n",
+				       __FUNCTION__, SYSCTL_BASENAME, devname);
+				kfree(scd);
+				kfree(salbuf);
+				continue;
+			}
+
+			class_simple_device_add(snsc_class, dev, NULL,
+						"%s", devname);
+
+			ia64_sn_irtr_intr_enable(scd->scd_nasid,
+						 0 /*ignored */ ,
+						 SAL_IROUTER_INTR_RECV);
+	}
+	return 0;
+}
+
+module_init(scdrv_init);