diff --git a/drivers/sn/ioc4.c b/drivers/sn/ioc4.c
index d9e4ee2..70862d7 100644
--- a/drivers/sn/ioc4.c
+++ b/drivers/sn/ioc4.c
@@ -6,60 +6,294 @@
  * Copyright (C) 2005 Silicon Graphics, Inc.  All Rights Reserved.
  */
 
-/*
- * This file contains a shim driver for the IOC4 IDE and serial drivers.
+/* This file contains the master driver module for use by SGI IOC4 subdrivers.
+ *
+ * It allocates any resources shared between multiple subdevices, and
+ * provides accessor functions (where needed) and the like for those
+ * resources.  It also provides a mechanism for the subdevice modules
+ * to support loading and unloading.
+ *
+ * Non-shared resources (e.g. external interrupt A_INT_OUT register page
+ * alias, serial port and UART registers) are handled by the subdevice
+ * modules themselves.
+ *
+ * This is all necessary because IOC4 is not implemented as a multi-function
+ * PCI device, but an amalgamation of disparate registers for several
+ * types of device (ATA, serial, external interrupts).  The normal
+ * resource management in the kernel doesn't have quite the right interfaces
+ * to handle this situation (e.g. multiple modules can't claim the same
+ * PCI ID), thus this IOC4 master module.
  */
 
 #include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/pci.h>
-#include <linux/ioc4_common.h>
-#include <linux/ide.h>
+#include <linux/ioc4.h>
+#include <linux/rwsem.h>
 
+/************************
+ * Submodule management *
+ ************************/
 
-static int __devinit
-ioc4_probe_one(struct pci_dev *pdev, const struct pci_device_id *pci_id)
+static LIST_HEAD(ioc4_devices);
+static DECLARE_RWSEM(ioc4_devices_rwsem);
+
+static LIST_HEAD(ioc4_submodules);
+static DECLARE_RWSEM(ioc4_submodules_rwsem);
+
+/* Register an IOC4 submodule */
+int
+ioc4_register_submodule(struct ioc4_submodule *is)
 {
+	struct ioc4_driver_data *idd;
+
+	down_write(&ioc4_submodules_rwsem);
+	list_add(&is->is_list, &ioc4_submodules);
+	up_write(&ioc4_submodules_rwsem);
+
+	/* Initialize submodule for each IOC4 */
+	if (!is->is_probe)
+		return 0;
+
+	down_read(&ioc4_devices_rwsem);
+	list_for_each_entry(idd, &ioc4_devices, idd_list) {
+		if (is->is_probe(idd)) {
+			printk(KERN_WARNING
+			       "%s: IOC4 submodule %s probe failed "
+			       "for pci_dev %s",
+			       __FUNCTION__, module_name(is->is_owner),
+			       pci_name(idd->idd_pdev));
+		}
+	}
+	up_read(&ioc4_devices_rwsem);
+
+	return 0;
+}
+
+/* Unregister an IOC4 submodule */
+void
+ioc4_unregister_submodule(struct ioc4_submodule *is)
+{
+	struct ioc4_driver_data *idd;
+
+	down_write(&ioc4_submodules_rwsem);
+	list_del(&is->is_list);
+	up_write(&ioc4_submodules_rwsem);
+
+	/* Remove submodule for each IOC4 */
+	if (!is->is_remove)
+		return;
+
+	down_read(&ioc4_devices_rwsem);
+	list_for_each_entry(idd, &ioc4_devices, idd_list) {
+		if (is->is_remove(idd)) {
+			printk(KERN_WARNING
+			       "%s: IOC4 submodule %s remove failed "
+			       "for pci_dev %s.\n",
+			       __FUNCTION__, module_name(is->is_owner),
+			       pci_name(idd->idd_pdev));
+		}
+	}
+	up_read(&ioc4_devices_rwsem);
+}
+
+/*********************
+ * Device management *
+ *********************/
+
+/* Adds a new instance of an IOC4 card */
+static int
+ioc4_probe(struct pci_dev *pdev, const struct pci_device_id *pci_id)
+{
+	struct ioc4_driver_data *idd;
+	struct ioc4_submodule *is;
+	uint32_t pcmd;
 	int ret;
 
+	/* Enable IOC4 and take ownership of it */
 	if ((ret = pci_enable_device(pdev))) {
 		printk(KERN_WARNING
-			 "%s: Failed to enable device with "
-				"pci_dev 0x%p... returning\n",
-				__FUNCTION__, (void *)pdev);
-		return ret;
+		       "%s: Failed to enable IOC4 device for pci_dev %s.\n",
+		       __FUNCTION__, pci_name(pdev));
+		goto out;
 	}
 	pci_set_master(pdev);
 
-	/* attach each sub-device */
-	ret = ioc4_ide_attach_one(pdev, pci_id);
-	if (ret)
-		return ret;
-	return ioc4_serial_attach_one(pdev, pci_id);
+	/* Set up per-IOC4 data */
+	idd = kmalloc(sizeof(struct ioc4_driver_data), GFP_KERNEL);
+	if (!idd) {
+		printk(KERN_WARNING
+		       "%s: Failed to allocate IOC4 data for pci_dev %s.\n",
+		       __FUNCTION__, pci_name(pdev));
+		ret = -ENODEV;
+		goto out_idd;
+	}
+	idd->idd_pdev = pdev;
+	idd->idd_pci_id = pci_id;
+
+	/* Map IOC4 misc registers.  These are shared between subdevices
+	 * so the main IOC4 module manages them.
+	 */
+	idd->idd_bar0 = pci_resource_start(idd->idd_pdev, 0);
+	if (!idd->idd_bar0) {
+		printk(KERN_WARNING
+		       "%s: Unable to find IOC4 misc resource "
+		       "for pci_dev %s.\n",
+		       __FUNCTION__, pci_name(idd->idd_pdev));
+		ret = -ENODEV;
+		goto out_pci;
+	}
+	if (!request_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs),
+			    "ioc4_misc")) {
+		printk(KERN_WARNING
+		       "%s: Unable to request IOC4 misc region "
+		       "for pci_dev %s.\n",
+		       __FUNCTION__, pci_name(idd->idd_pdev));
+		ret = -ENODEV;
+		goto out_pci;
+	}
+	idd->idd_misc_regs = ioremap(idd->idd_bar0,
+				     sizeof(struct ioc4_misc_regs));
+	if (!idd->idd_misc_regs) {
+		printk(KERN_WARNING
+		       "%s: Unable to remap IOC4 misc region "
+		       "for pci_dev %s.\n",
+		       __FUNCTION__, pci_name(idd->idd_pdev));
+		ret = -ENODEV;
+		goto out_misc_region;
+	}
+
+	/* Failsafe portion of per-IOC4 initialization */
+
+	/* Initialize IOC4 */
+	pci_read_config_dword(idd->idd_pdev, PCI_COMMAND, &pcmd);
+	pci_write_config_dword(idd->idd_pdev, PCI_COMMAND,
+			       pcmd | PCI_COMMAND_PARITY | PCI_COMMAND_SERR);
+
+	/* Disable/clear all interrupts.  Need to do this here lest
+	 * one submodule request the shared IOC4 IRQ, but interrupt
+	 * is generated by a different subdevice.
+	 */
+	/* Disable */
+	writel(~0, &idd->idd_misc_regs->other_iec.raw);
+	writel(~0, &idd->idd_misc_regs->sio_iec);
+	/* Clear (i.e. acknowledge) */
+	writel(~0, &idd->idd_misc_regs->other_ir.raw);
+	writel(~0, &idd->idd_misc_regs->sio_ir);
+
+	/* Track PCI-device specific data */
+	idd->idd_serial_data = NULL;
+	pci_set_drvdata(idd->idd_pdev, idd);
+	down_write(&ioc4_devices_rwsem);
+	list_add(&idd->idd_list, &ioc4_devices);
+	up_write(&ioc4_devices_rwsem);
+
+	/* Add this IOC4 to all submodules */
+	down_read(&ioc4_submodules_rwsem);
+	list_for_each_entry(is, &ioc4_submodules, is_list) {
+		if (is->is_probe && is->is_probe(idd)) {
+			printk(KERN_WARNING
+			       "%s: IOC4 submodule 0x%s probe failed "
+			       "for pci_dev %s.\n",
+			       __FUNCTION__, module_name(is->is_owner),
+			       pci_name(idd->idd_pdev));
+		}
+	}
+	up_read(&ioc4_submodules_rwsem);
+
+	return 0;
+
+out_misc_region:
+	release_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs));
+out_pci:
+	kfree(idd);
+out_idd:
+	pci_disable_device(pdev);
+out:
+	return ret;
 }
 
-/* pci device struct */
-static struct pci_device_id ioc4_s_id_table[] = {
+/* Removes a particular instance of an IOC4 card. */
+static void
+ioc4_remove(struct pci_dev *pdev)
+{
+	struct ioc4_submodule *is;
+	struct ioc4_driver_data *idd;
+
+	idd = pci_get_drvdata(pdev);
+
+	/* Remove this IOC4 from all submodules */
+	down_read(&ioc4_submodules_rwsem);
+	list_for_each_entry(is, &ioc4_submodules, is_list) {
+		if (is->is_remove && is->is_remove(idd)) {
+			printk(KERN_WARNING
+			       "%s: IOC4 submodule 0x%s remove failed "
+			       "for pci_dev %s.\n",
+			       __FUNCTION__, module_name(is->is_owner),
+			       pci_name(idd->idd_pdev));
+		}
+	}
+	up_read(&ioc4_submodules_rwsem);
+
+	/* Release resources */
+	iounmap(idd->idd_misc_regs);
+	if (!idd->idd_bar0) {
+		printk(KERN_WARNING
+		       "%s: Unable to get IOC4 misc mapping for pci_dev %s. "
+		       "Device removal may be incomplete.\n",
+		       __FUNCTION__, pci_name(idd->idd_pdev));
+	}
+	release_region(idd->idd_bar0, sizeof(struct ioc4_misc_regs));
+
+	/* Disable IOC4 and relinquish */
+	pci_disable_device(pdev);
+
+	/* Remove and free driver data */
+	down_write(&ioc4_devices_rwsem);
+	list_del(&idd->idd_list);
+	up_write(&ioc4_devices_rwsem);
+	kfree(idd);
+}
+
+static struct pci_device_id ioc4_id_table[] = {
 	{PCI_VENDOR_ID_SGI, PCI_DEVICE_ID_SGI_IOC4, PCI_ANY_ID,
 	 PCI_ANY_ID, 0x0b4000, 0xFFFFFF},
 	{0}
 };
-MODULE_DEVICE_TABLE(pci, ioc4_s_id_table);
 
-static struct pci_driver __devinitdata ioc4_s_driver = {
-	.name	= "IOC4",
-	.id_table = ioc4_s_id_table,
-	.probe	= ioc4_probe_one,
+static struct pci_driver __devinitdata ioc4_driver = {
+	.name = "IOC4",
+	.id_table = ioc4_id_table,
+	.probe = ioc4_probe,
+	.remove = ioc4_remove,
 };
 
-static int __devinit ioc4_detect(void)
+MODULE_DEVICE_TABLE(pci, ioc4_id_table);
+
+/*********************
+ * Module management *
+ *********************/
+
+/* Module load */
+static int __devinit
+ioc4_init(void)
 {
-	ioc4_serial_init();
-
-	return pci_register_driver(&ioc4_s_driver);
+	return pci_register_driver(&ioc4_driver);
 }
-module_init(ioc4_detect);
 
-MODULE_AUTHOR("Pat Gefre - Silicon Graphics Inc. (SGI) <pfg@sgi.com>");
-MODULE_DESCRIPTION("PCI driver module for SGI IOC4 Base-IO Card");
+/* Module unload */
+static void __devexit
+ioc4_exit(void)
+{
+	pci_unregister_driver(&ioc4_driver);
+}
+
+module_init(ioc4_init);
+module_exit(ioc4_exit);
+
+MODULE_AUTHOR("Brent Casavant - Silicon Graphics, Inc. <bcasavan@sgi.com>");
+MODULE_DESCRIPTION("PCI driver master module for SGI IOC4 Base-IO Card");
 MODULE_LICENSE("GPL");
+
+EXPORT_SYMBOL(ioc4_register_submodule);
+EXPORT_SYMBOL(ioc4_unregister_submodule);