/* -*- linux-c -*-
 * viodasd.c
 *  Authors: Dave Boutcher <boutcher@us.ibm.com>
 *           Ryan Arnold <ryanarn@us.ibm.com>
 *           Colin Devilbiss <devilbis@us.ibm.com>
 *           Stephen Rothwell
 *
 * (C) Copyright 2000-2004 IBM Corporation
 *
 * 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
 *
 * This routine provides access to disk space (termed "DASD" in historical
 * IBM terms) owned and managed by an OS/400 partition running on the
 * same box as this Linux partition.
 *
 * All disk operations are performed by sending messages back and forth to
 * the OS/400 partition.
 */

#define pr_fmt(fmt) "viod: " fmt

#include <linux/major.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/genhd.h>
#include <linux/hdreg.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/dma-mapping.h>
#include <linux/completion.h>
#include <linux/device.h>
#include <linux/scatterlist.h>

#include <asm/uaccess.h>
#include <asm/vio.h>
#include <asm/iseries/hv_types.h>
#include <asm/iseries/hv_lp_event.h>
#include <asm/iseries/hv_lp_config.h>
#include <asm/iseries/vio.h>
#include <asm/firmware.h>

MODULE_DESCRIPTION("iSeries Virtual DASD");
MODULE_AUTHOR("Dave Boutcher");
MODULE_LICENSE("GPL");

/*
 * We only support 7 partitions per physical disk....so with minor
 * numbers 0-255 we get a maximum of 32 disks.
 */
#define VIOD_GENHD_NAME		"iseries/vd"

#define VIOD_VERS		"1.64"

enum {
	PARTITION_SHIFT = 3,
	MAX_DISKNO = HVMAXARCHITECTEDVIRTUALDISKS,
	MAX_DISK_NAME = FIELD_SIZEOF(struct gendisk, disk_name)
};

static DEFINE_SPINLOCK(viodasd_spinlock);

#define VIOMAXREQ		16

#define DEVICE_NO(cell)	((struct viodasd_device *)(cell) - &viodasd_devices[0])

struct viodasd_waitevent {
	struct completion	com;
	int			rc;
	u16			sub_result;
	int			max_disk;	/* open */
};

static const struct vio_error_entry viodasd_err_table[] = {
	{ 0x0201, EINVAL, "Invalid Range" },
	{ 0x0202, EINVAL, "Invalid Token" },
	{ 0x0203, EIO, "DMA Error" },
	{ 0x0204, EIO, "Use Error" },
	{ 0x0205, EIO, "Release Error" },
	{ 0x0206, EINVAL, "Invalid Disk" },
	{ 0x0207, EBUSY, "Cant Lock" },
	{ 0x0208, EIO, "Already Locked" },
	{ 0x0209, EIO, "Already Unlocked" },
	{ 0x020A, EIO, "Invalid Arg" },
	{ 0x020B, EIO, "Bad IFS File" },
	{ 0x020C, EROFS, "Read Only Device" },
	{ 0x02FF, EIO, "Internal Error" },
	{ 0x0000, 0, NULL },
};

/*
 * Figure out the biggest I/O request (in sectors) we can accept
 */
#define VIODASD_MAXSECTORS (4096 / 512 * VIOMAXBLOCKDMA)

/*
 * Number of disk I/O requests we've sent to OS/400
 */
static int num_req_outstanding;

/*
 * This is our internal structure for keeping track of disk devices
 */
struct viodasd_device {
	u16		cylinders;
	u16		tracks;
	u16		sectors;
	u16		bytes_per_sector;
	u64		size;
	int		read_only;
	spinlock_t	q_lock;
	struct gendisk	*disk;
	struct device	*dev;
} viodasd_devices[MAX_DISKNO];

/*
 * External open entry point.
 */
static int viodasd_open(struct block_device *bdev, fmode_t mode)
{
	struct viodasd_device *d = bdev->bd_disk->private_data;
	HvLpEvent_Rc hvrc;
	struct viodasd_waitevent we;
	u16 flags = 0;

	if (d->read_only) {
		if (mode & FMODE_WRITE)
			return -EROFS;
		flags = vioblockflags_ro;
	}

	init_completion(&we.com);

	/* Send the open event to OS/400 */
	hvrc = HvCallEvent_signalLpEventFast(viopath_hostLp,
			HvLpEvent_Type_VirtualIo,
			viomajorsubtype_blockio | vioblockopen,
			HvLpEvent_AckInd_DoAck, HvLpEvent_AckType_ImmediateAck,
			viopath_sourceinst(viopath_hostLp),
			viopath_targetinst(viopath_hostLp),
			(u64)(unsigned long)&we, VIOVERSION << 16,
			((u64)DEVICE_NO(d) << 48) | ((u64)flags << 32),
			0, 0, 0);
	if (hvrc != 0) {
		pr_warning("HV open failed %d\n", (int)hvrc);
		return -EIO;
	}

	wait_for_completion(&we.com);

	/* Check the return code */
	if (we.rc != 0) {
		const struct vio_error_entry *err =
			vio_lookup_rc(viodasd_err_table, we.sub_result);

		pr_warning("bad rc opening disk: %d:0x%04x (%s)\n",
			   (int)we.rc, we.sub_result, err->msg);
		return -EIO;
	}

	return 0;
}

/*
 * External release entry point.
 */
static int viodasd_release(struct gendisk *disk, fmode_t mode)
{
	struct viodasd_device *d = disk->private_data;
	HvLpEvent_Rc hvrc;

	/* Send the event to OS/400.  We DON'T expect a response */
	hvrc = HvCallEvent_signalLpEventFast(viopath_hostLp,
			HvLpEvent_Type_VirtualIo,
			viomajorsubtype_blockio | vioblockclose,
			HvLpEvent_AckInd_NoAck, HvLpEvent_AckType_ImmediateAck,
			viopath_sourceinst(viopath_hostLp),
			viopath_targetinst(viopath_hostLp),
			0, VIOVERSION << 16,
			((u64)DEVICE_NO(d) << 48) /* | ((u64)flags << 32) */,
			0, 0, 0);
	if (hvrc != 0)
		pr_warning("HV close call failed %d\n", (int)hvrc);
	return 0;
}


/* External ioctl entry point.
 */
static int viodasd_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
	struct gendisk *disk = bdev->bd_disk;
	struct viodasd_device *d = disk->private_data;

	geo->sectors = d->sectors ? d->sectors : 32;
	geo->heads = d->tracks ? d->tracks  : 64;
	geo->cylinders = d->cylinders ? d->cylinders :
		get_capacity(disk) / (geo->sectors * geo->heads);

	return 0;
}

/*
 * Our file operations table
 */
static const struct block_device_operations viodasd_fops = {
	.owner = THIS_MODULE,
	.open = viodasd_open,
	.release = viodasd_release,
	.getgeo = viodasd_getgeo,
};

/*
 * End a request
 */
static void viodasd_end_request(struct request *req, int error,
		int num_sectors)
{
	__blk_end_request(req, error, num_sectors << 9);
}

/*
 * Send an actual I/O request to OS/400
 */
static int send_request(struct request *req)
{
	u64 start;
	int direction;
	int nsg;
	u16 viocmd;
	HvLpEvent_Rc hvrc;
	struct vioblocklpevent *bevent;
	struct HvLpEvent *hev;
	struct scatterlist sg[VIOMAXBLOCKDMA];
	int sgindex;
	struct viodasd_device *d;
	unsigned long flags;

	start = (u64)blk_rq_pos(req) << 9;

	if (rq_data_dir(req) == READ) {
		direction = DMA_FROM_DEVICE;
		viocmd = viomajorsubtype_blockio | vioblockread;
	} else {
		direction = DMA_TO_DEVICE;
		viocmd = viomajorsubtype_blockio | vioblockwrite;
	}

        d = req->rq_disk->private_data;

	/* Now build the scatter-gather list */
	sg_init_table(sg, VIOMAXBLOCKDMA);
	nsg = blk_rq_map_sg(req->q, req, sg);
	nsg = dma_map_sg(d->dev, sg, nsg, direction);

	spin_lock_irqsave(&viodasd_spinlock, flags);
	num_req_outstanding++;

	/* This optimization handles a single DMA block */
	if (nsg == 1)
		hvrc = HvCallEvent_signalLpEventFast(viopath_hostLp,
				HvLpEvent_Type_VirtualIo, viocmd,
				HvLpEvent_AckInd_DoAck,
				HvLpEvent_AckType_ImmediateAck,
				viopath_sourceinst(viopath_hostLp),
				viopath_targetinst(viopath_hostLp),
				(u64)(unsigned long)req, VIOVERSION << 16,
				((u64)DEVICE_NO(d) << 48), start,
				((u64)sg_dma_address(&sg[0])) << 32,
				sg_dma_len(&sg[0]));
	else {
		bevent = (struct vioblocklpevent *)
			vio_get_event_buffer(viomajorsubtype_blockio);
		if (bevent == NULL) {
			pr_warning("error allocating disk event buffer\n");
			goto error_ret;
		}

		/*
		 * Now build up the actual request.  Note that we store
		 * the pointer to the request in the correlation
		 * token so we can match the response up later
		 */
		memset(bevent, 0, sizeof(struct vioblocklpevent));
		hev = &bevent->event;
		hev->flags = HV_LP_EVENT_VALID | HV_LP_EVENT_DO_ACK |
			HV_LP_EVENT_INT;
		hev->xType = HvLpEvent_Type_VirtualIo;
		hev->xSubtype = viocmd;
		hev->xSourceLp = HvLpConfig_getLpIndex();
		hev->xTargetLp = viopath_hostLp;
		hev->xSizeMinus1 =
			offsetof(struct vioblocklpevent, u.rw_data.dma_info) +
			(sizeof(bevent->u.rw_data.dma_info[0]) * nsg) - 1;
		hev->xSourceInstanceId = viopath_sourceinst(viopath_hostLp);
		hev->xTargetInstanceId = viopath_targetinst(viopath_hostLp);
		hev->xCorrelationToken = (u64)req;
		bevent->version = VIOVERSION;
		bevent->disk = DEVICE_NO(d);
		bevent->u.rw_data.offset = start;

		/*
		 * Copy just the dma information from the sg list
		 * into the request
		 */
		for (sgindex = 0; sgindex < nsg; sgindex++) {
			bevent->u.rw_data.dma_info[sgindex].token =
				sg_dma_address(&sg[sgindex]);
			bevent->u.rw_data.dma_info[sgindex].len =
				sg_dma_len(&sg[sgindex]);
		}

		/* Send the request */
		hvrc = HvCallEvent_signalLpEvent(&bevent->event);
		vio_free_event_buffer(viomajorsubtype_blockio, bevent);
	}

	if (hvrc != HvLpEvent_Rc_Good) {
		pr_warning("error sending disk event to OS/400 (rc %d)\n",
			   (int)hvrc);
		goto error_ret;
	}
	spin_unlock_irqrestore(&viodasd_spinlock, flags);
	return 0;

error_ret:
	num_req_outstanding--;
	spin_unlock_irqrestore(&viodasd_spinlock, flags);
	dma_unmap_sg(d->dev, sg, nsg, direction);
	return -1;
}

/*
 * This is the external request processing routine
 */
static void do_viodasd_request(struct request_queue *q)
{
	struct request *req;

	/*
	 * If we already have the maximum number of requests
	 * outstanding to OS/400 just bail out. We'll come
	 * back later.
	 */
	while (num_req_outstanding < VIOMAXREQ) {
		req = blk_fetch_request(q);
		if (req == NULL)
			return;
		/* check that request contains a valid command */
		if (!blk_fs_request(req)) {
			viodasd_end_request(req, -EIO, blk_rq_sectors(req));
			continue;
		}
		/* Try sending the request */
		if (send_request(req) != 0)
			viodasd_end_request(req, -EIO, blk_rq_sectors(req));
	}
}

/*
 * Probe a single disk and fill in the viodasd_device structure
 * for it.
 */
static int probe_disk(struct viodasd_device *d)
{
	HvLpEvent_Rc hvrc;
	struct viodasd_waitevent we;
	int dev_no = DEVICE_NO(d);
	struct gendisk *g;
	struct request_queue *q;
	u16 flags = 0;

retry:
	init_completion(&we.com);

	/* Send the open event to OS/400 */
	hvrc = HvCallEvent_signalLpEventFast(viopath_hostLp,
			HvLpEvent_Type_VirtualIo,
			viomajorsubtype_blockio | vioblockopen,
			HvLpEvent_AckInd_DoAck, HvLpEvent_AckType_ImmediateAck,
			viopath_sourceinst(viopath_hostLp),
			viopath_targetinst(viopath_hostLp),
			(u64)(unsigned long)&we, VIOVERSION << 16,
			((u64)dev_no << 48) | ((u64)flags<< 32),
			0, 0, 0);
	if (hvrc != 0) {
		pr_warning("bad rc on HV open %d\n", (int)hvrc);
		return 0;
	}

	wait_for_completion(&we.com);

	if (we.rc != 0) {
		if (flags != 0)
			return 0;
		/* try again with read only flag set */
		flags = vioblockflags_ro;
		goto retry;
	}
	if (we.max_disk > (MAX_DISKNO - 1)) {
		printk_once(KERN_INFO pr_fmt("Only examining the first %d of %d disks connected\n"),
			    MAX_DISKNO, we.max_disk + 1);
	}

	/* Send the close event to OS/400.  We DON'T expect a response */
	hvrc = HvCallEvent_signalLpEventFast(viopath_hostLp,
			HvLpEvent_Type_VirtualIo,
			viomajorsubtype_blockio | vioblockclose,
			HvLpEvent_AckInd_NoAck, HvLpEvent_AckType_ImmediateAck,
			viopath_sourceinst(viopath_hostLp),
			viopath_targetinst(viopath_hostLp),
			0, VIOVERSION << 16,
			((u64)dev_no << 48) | ((u64)flags << 32),
			0, 0, 0);
	if (hvrc != 0) {
		pr_warning("bad rc sending event to OS/400 %d\n", (int)hvrc);
		return 0;
	}

	if (d->dev == NULL) {
		/* this is when we reprobe for new disks */
		if (vio_create_viodasd(dev_no) == NULL) {
			pr_warning("cannot allocate virtual device for disk %d\n",
				   dev_no);
			return 0;
		}
		/*
		 * The vio_create_viodasd will have recursed into this
		 * routine with d->dev set to the new vio device and
		 * will finish the setup of the disk below.
		 */
		return 1;
	}

	/* create the request queue for the disk */
	spin_lock_init(&d->q_lock);
	q = blk_init_queue(do_viodasd_request, &d->q_lock);
	if (q == NULL) {
		pr_warning("cannot allocate queue for disk %d\n", dev_no);
		return 0;
	}
	g = alloc_disk(1 << PARTITION_SHIFT);
	if (g == NULL) {
		pr_warning("cannot allocate disk structure for disk %d\n",
			   dev_no);
		blk_cleanup_queue(q);
		return 0;
	}

	d->disk = g;
	blk_queue_max_segments(q, VIOMAXBLOCKDMA);
	blk_queue_max_hw_sectors(q, VIODASD_MAXSECTORS);
	g->major = VIODASD_MAJOR;
	g->first_minor = dev_no << PARTITION_SHIFT;
	if (dev_no >= 26)
		snprintf(g->disk_name, sizeof(g->disk_name),
				VIOD_GENHD_NAME "%c%c",
				'a' + (dev_no / 26) - 1, 'a' + (dev_no % 26));
	else
		snprintf(g->disk_name, sizeof(g->disk_name),
				VIOD_GENHD_NAME "%c", 'a' + (dev_no % 26));
	g->fops = &viodasd_fops;
	g->queue = q;
	g->private_data = d;
	g->driverfs_dev = d->dev;
	set_capacity(g, d->size >> 9);

	pr_info("disk %d: %lu sectors (%lu MB) CHS=%d/%d/%d sector size %d%s\n",
		dev_no, (unsigned long)(d->size >> 9),
		(unsigned long)(d->size >> 20),
		(int)d->cylinders, (int)d->tracks,
		(int)d->sectors, (int)d->bytes_per_sector,
		d->read_only ? " (RO)" : "");

	/* register us in the global list */
	add_disk(g);
	return 1;
}

/* returns the total number of scatterlist elements converted */
static int block_event_to_scatterlist(const struct vioblocklpevent *bevent,
		struct scatterlist *sg, int *total_len)
{
	int i, numsg;
	const struct rw_data *rw_data = &bevent->u.rw_data;
	static const int offset =
		offsetof(struct vioblocklpevent, u.rw_data.dma_info);
	static const int element_size = sizeof(rw_data->dma_info[0]);

	numsg = ((bevent->event.xSizeMinus1 + 1) - offset) / element_size;
	if (numsg > VIOMAXBLOCKDMA)
		numsg = VIOMAXBLOCKDMA;

	*total_len = 0;
	sg_init_table(sg, VIOMAXBLOCKDMA);
	for (i = 0; (i < numsg) && (rw_data->dma_info[i].len > 0); ++i) {
		sg_dma_address(&sg[i]) = rw_data->dma_info[i].token;
		sg_dma_len(&sg[i]) = rw_data->dma_info[i].len;
		*total_len += rw_data->dma_info[i].len;
	}
	return i;
}

/*
 * Restart all queues, starting with the one _after_ the disk given,
 * thus reducing the chance of starvation of higher numbered disks.
 */
static void viodasd_restart_all_queues_starting_from(int first_index)
{
	int i;

	for (i = first_index + 1; i < MAX_DISKNO; ++i)
		if (viodasd_devices[i].disk)
			blk_run_queue(viodasd_devices[i].disk->queue);
	for (i = 0; i <= first_index; ++i)
		if (viodasd_devices[i].disk)
			blk_run_queue(viodasd_devices[i].disk->queue);
}

/*
 * For read and write requests, decrement the number of outstanding requests,
 * Free the DMA buffers we allocated.
 */
static int viodasd_handle_read_write(struct vioblocklpevent *bevent)
{
	int num_sg, num_sect, pci_direction, total_len;
	struct request *req;
	struct scatterlist sg[VIOMAXBLOCKDMA];
	struct HvLpEvent *event = &bevent->event;
	unsigned long irq_flags;
	struct viodasd_device *d;
	int error;
	spinlock_t *qlock;

	num_sg = block_event_to_scatterlist(bevent, sg, &total_len);
	num_sect = total_len >> 9;
	if (event->xSubtype == (viomajorsubtype_blockio | vioblockread))
		pci_direction = DMA_FROM_DEVICE;
	else
		pci_direction = DMA_TO_DEVICE;
	req = (struct request *)bevent->event.xCorrelationToken;
	d = req->rq_disk->private_data;

	dma_unmap_sg(d->dev, sg, num_sg, pci_direction);

	/*
	 * Since this is running in interrupt mode, we need to make sure
	 * we're not stepping on any global I/O operations
	 */
	spin_lock_irqsave(&viodasd_spinlock, irq_flags);
	num_req_outstanding--;
	spin_unlock_irqrestore(&viodasd_spinlock, irq_flags);

	error = (event->xRc == HvLpEvent_Rc_Good) ? 0 : -EIO;
	if (error) {
		const struct vio_error_entry *err;
		err = vio_lookup_rc(viodasd_err_table, bevent->sub_result);
		pr_warning("read/write error %d:0x%04x (%s)\n",
			   event->xRc, bevent->sub_result, err->msg);
		num_sect = blk_rq_sectors(req);
	}
	qlock = req->q->queue_lock;
	spin_lock_irqsave(qlock, irq_flags);
	viodasd_end_request(req, error, num_sect);
	spin_unlock_irqrestore(qlock, irq_flags);

	/* Finally, try to get more requests off of this device's queue */
	viodasd_restart_all_queues_starting_from(DEVICE_NO(d));

	return 0;
}

/* This routine handles incoming block LP events */
static void handle_block_event(struct HvLpEvent *event)
{
	struct vioblocklpevent *bevent = (struct vioblocklpevent *)event;
	struct viodasd_waitevent *pwe;

	if (event == NULL)
		/* Notification that a partition went away! */
		return;
	/* First, we should NEVER get an int here...only acks */
	if (hvlpevent_is_int(event)) {
		pr_warning("Yikes! got an int in viodasd event handler!\n");
		if (hvlpevent_need_ack(event)) {
			event->xRc = HvLpEvent_Rc_InvalidSubtype;
			HvCallEvent_ackLpEvent(event);
		}
	}

	switch (event->xSubtype & VIOMINOR_SUBTYPE_MASK) {
	case vioblockopen:
		/*
		 * Handle a response to an open request.  We get all the
		 * disk information in the response, so update it.  The
		 * correlation token contains a pointer to a waitevent
		 * structure that has a completion in it.  update the
		 * return code in the waitevent structure and post the
		 * completion to wake up the guy who sent the request
		 */
		pwe = (struct viodasd_waitevent *)event->xCorrelationToken;
		pwe->rc = event->xRc;
		pwe->sub_result = bevent->sub_result;
		if (event->xRc == HvLpEvent_Rc_Good) {
			const struct open_data *data = &bevent->u.open_data;
			struct viodasd_device *device =
				&viodasd_devices[bevent->disk];
			device->read_only =
				bevent->flags & vioblockflags_ro;
			device->size = data->disk_size;
			device->cylinders = data->cylinders;
			device->tracks = data->tracks;
			device->sectors = data->sectors;
			device->bytes_per_sector = data->bytes_per_sector;
			pwe->max_disk = data->max_disk;
		}
		complete(&pwe->com);
		break;
	case vioblockclose:
		break;
	case vioblockread:
	case vioblockwrite:
		viodasd_handle_read_write(bevent);
		break;

	default:
		pr_warning("invalid subtype!");
		if (hvlpevent_need_ack(event)) {
			event->xRc = HvLpEvent_Rc_InvalidSubtype;
			HvCallEvent_ackLpEvent(event);
		}
	}
}

/*
 * Get the driver to reprobe for more disks.
 */
static ssize_t probe_disks(struct device_driver *drv, const char *buf,
		size_t count)
{
	struct viodasd_device *d;

	for (d = viodasd_devices; d < &viodasd_devices[MAX_DISKNO]; d++) {
		if (d->disk == NULL)
			probe_disk(d);
	}
	return count;
}
static DRIVER_ATTR(probe, S_IWUSR, NULL, probe_disks);

static int viodasd_probe(struct vio_dev *vdev, const struct vio_device_id *id)
{
	struct viodasd_device *d = &viodasd_devices[vdev->unit_address];

	d->dev = &vdev->dev;
	if (!probe_disk(d))
		return -ENODEV;
	return 0;
}

static int viodasd_remove(struct vio_dev *vdev)
{
	struct viodasd_device *d;

	d = &viodasd_devices[vdev->unit_address];
	if (d->disk) {
		del_gendisk(d->disk);
		blk_cleanup_queue(d->disk->queue);
		put_disk(d->disk);
		d->disk = NULL;
	}
	d->dev = NULL;
	return 0;
}

/**
 * viodasd_device_table: Used by vio.c to match devices that we
 * support.
 */
static struct vio_device_id viodasd_device_table[] __devinitdata = {
	{ "block", "IBM,iSeries-viodasd" },
	{ "", "" }
};
MODULE_DEVICE_TABLE(vio, viodasd_device_table);

static struct vio_driver viodasd_driver = {
	.id_table = viodasd_device_table,
	.probe = viodasd_probe,
	.remove = viodasd_remove,
	.driver = {
		.name = "viodasd",
		.owner = THIS_MODULE,
	}
};

static int need_delete_probe;

/*
 * Initialize the whole device driver.  Handle module and non-module
 * versions
 */
static int __init viodasd_init(void)
{
	int rc;

	if (!firmware_has_feature(FW_FEATURE_ISERIES)) {
		rc = -ENODEV;
		goto early_fail;
	}

	/* Try to open to our host lp */
	if (viopath_hostLp == HvLpIndexInvalid)
		vio_set_hostlp();

	if (viopath_hostLp == HvLpIndexInvalid) {
		pr_warning("invalid hosting partition\n");
		rc = -EIO;
		goto early_fail;
	}

	pr_info("vers " VIOD_VERS ", hosting partition %d\n", viopath_hostLp);

        /* register the block device */
	rc =  register_blkdev(VIODASD_MAJOR, VIOD_GENHD_NAME);
	if (rc) {
		pr_warning("Unable to get major number %d for %s\n",
			   VIODASD_MAJOR, VIOD_GENHD_NAME);
		goto early_fail;
	}
	/* Actually open the path to the hosting partition */
	rc = viopath_open(viopath_hostLp, viomajorsubtype_blockio,
				VIOMAXREQ + 2);
	if (rc) {
		pr_warning("error opening path to host partition %d\n",
			   viopath_hostLp);
		goto unregister_blk;
	}

	/* Initialize our request handler */
	vio_setHandler(viomajorsubtype_blockio, handle_block_event);

	rc = vio_register_driver(&viodasd_driver);
	if (rc) {
		pr_warning("vio_register_driver failed\n");
		goto unset_handler;
	}

	/*
	 * If this call fails, it just means that we cannot dynamically
	 * add virtual disks, but the driver will still work fine for
	 * all existing disk, so ignore the failure.
	 */
	if (!driver_create_file(&viodasd_driver.driver, &driver_attr_probe))
		need_delete_probe = 1;

	return 0;

unset_handler:
	vio_clearHandler(viomajorsubtype_blockio);
	viopath_close(viopath_hostLp, viomajorsubtype_blockio, VIOMAXREQ + 2);
unregister_blk:
	unregister_blkdev(VIODASD_MAJOR, VIOD_GENHD_NAME);
early_fail:
	return rc;
}
module_init(viodasd_init);

void __exit viodasd_exit(void)
{
	if (need_delete_probe)
		driver_remove_file(&viodasd_driver.driver, &driver_attr_probe);
	vio_unregister_driver(&viodasd_driver);
	vio_clearHandler(viomajorsubtype_blockio);
	viopath_close(viopath_hostLp, viomajorsubtype_blockio, VIOMAXREQ + 2);
	unregister_blkdev(VIODASD_MAJOR, VIOD_GENHD_NAME);
}
module_exit(viodasd_exit);