From: Mike Christie <[email-masked]>

Multipath support for LSI RDAC.

[FIXME: Needs proper desciption of patch.  Engenio?]

Signed-off-by: Mike Christie <[email-masked]>
Cc: Chandra Seetharaman <[email-masked]>
Signed-off-by: Alasdair G Kergon <[email-masked]>

---
 drivers/md/Kconfig         |    6 
 drivers/md/Makefile        |    1 
 drivers/md/dm-mpath-rdac.c |  815 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 822 insertions(+)

Index: linux/drivers/md/Kconfig
===================================================================
--- linux.orig/drivers/md/Kconfig	2007-06-07 18:47:10.000000000 +0100
+++ linux/drivers/md/Kconfig	2007-06-07 18:47:25.000000000 +0100
@@ -262,6 +262,12 @@ config DM_MULTIPATH_EMC
 	---help---
 	  Multipath support for EMC CX/AX series hardware.
 
+config DM_MULTIPATH_RDAC
+	tristate "LSI RDAC multipath support (EXPERIMENTAL)"
+	depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
+	---help---
+	  Multipath support for LSI RDAC.
+
 config DM_DELAY
 	tristate "I/O delaying target (EXPERIMENTAL)"
 	depends on BLK_DEV_DM && EXPERIMENTAL
Index: linux/drivers/md/Makefile
===================================================================
--- linux.orig/drivers/md/Makefile	2007-06-07 18:47:10.000000000 +0100
+++ linux/drivers/md/Makefile	2007-06-07 18:47:25.000000000 +0100
@@ -34,6 +34,7 @@ obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
 obj-$(CONFIG_DM_DELAY)		+= dm-delay.o
 obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
 obj-$(CONFIG_DM_MULTIPATH_EMC)	+= dm-emc.o
+obj-$(CONFIG_DM_MULTIPATH_RDAC)	+= dm-mpath-rdac.o
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
 obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
Index: linux/drivers/md/dm-mpath-rdac.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux/drivers/md/dm-mpath-rdac.c	2007-06-07 18:47:25.000000000 +0100
@@ -0,0 +1,815 @@
+/*
+ * Engenio/LSI RDAC DM HW handler
+ *
+ * Copyright (C) 2005 Mike Christie. All rights reserved.
+ * Copyright (C) Chandra Seetharaman, IBM Corp. 2007
+ *
+ * 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 <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_eh.h>
+
+#define DM_MSG_PREFIX "multipath rdac"
+
+#include "dm.h"
+#include "dm-hw-handler.h"
+
+#define RDAC_DM_HWH_NAME "rdac"
+#define RDAC_DM_HWH_VER "0.4"
+
+/*
+ * LSI mode page stuff
+ *
+ * These struct definitions and the forming of the
+ * mode page were taken from the LSI RDAC 2.4 GPL'd
+ * driver, and then converted to Linux conventions.
+ */
+#define RDAC_QUIESCENCE_TIME 20;
+/*
+ * Page Codes
+ */
+#define RDAC_PAGE_CODE_REDUNDANT_CONTROLLER 0x2c
+
+/*
+ * Controller modes definitions
+ */
+#define RDAC_MODE_TRANSFER_ALL_LUNS		0x01
+#define RDAC_MODE_TRANSFER_SPECIFIED_LUNS	0x02
+
+/*
+ * RDAC Options field
+ */
+#define RDAC_FORCED_QUIESENCE 0x02
+
+/*
+ * default value TODO - make configurable
+ */
+#define RDAC_FAILOVER_TIMEOUT (60 * HZ)
+
+struct rdac_mode_6_hdr {
+	u8	data_len;
+	u8	medium_type;
+	u8	device_params;
+	u8	block_desc_len;
+};
+
+struct rdac_mode_10_hdr {
+	u16	data_len;
+	u8	medium_type;
+	u8	device_params;
+	u16	reserved;
+	u16	block_desc_len;
+};
+
+struct rdac_mode_common {
+	u8	controller_serial[16];
+	u8	alt_controller_serial[16];
+	u8	rdac_mode[2];
+	u8	alt_rdac_mode[2];
+	u8	quiescence_timeout;
+	u8	rdac_options;
+};
+
+struct rdac_pg_legacy {
+	struct rdac_mode_6_hdr hdr;
+	u8	page_code;
+	u8	page_len;
+	struct rdac_mode_common common;
+#define MODE6_MAX_LUN	32
+	u8	lun_table[MODE6_MAX_LUN];
+	u8	reserved2[32];
+	u8	reserved3;
+	u8	reserved4;
+};
+
+struct rdac_pg_expanded {
+	struct rdac_mode_10_hdr hdr;
+	u8	page_code;
+	u8	subpage_code;
+	u8	page_len[2];
+	struct rdac_mode_common common;
+	u8	lun_table[256];
+	u8	reserved3;
+	u8	reserved4;
+};
+
+struct c9_inquiry {
+	u8	peripheral_info;
+	u8	page_code;	/* 0xC9 */
+	u8	reserved1;
+	u8	page_len;
+	u8	page_id[4];	/* "vace" */
+	u8	avte_cvp;
+	u8	path_prio;
+	u8	reserved2[38];
+};
+
+#define SUBSYS_ID_LEN	16
+#define SLOT_ID_LEN	2
+
+struct c4_inquiry {
+	u8	peripheral_info;
+	u8	page_code;	/* 0xC4 */
+	u8	reserved1;
+	u8	page_len;
+	u8	page_id[4];	/* "subs" */
+	u8	subsys_id[SUBSYS_ID_LEN];
+	u8	revision[4];
+	u8	slot_id[SUBSYS_ID_LEN];
+	u8	reserved[2];
+};
+
+struct rdac_handler {
+	unsigned		timeout;
+	struct rdac_controller	*ctlr;
+#define UNINITIALIZED_LUN	(1 << 8)
+	unsigned		lun;
+	unsigned char		sense[SCSI_SENSE_BUFFERSIZE];
+};
+
+struct rdac_private {
+	struct request		*req;
+	struct rdac_handler	*h;
+	struct dm_path		*path;
+	struct list_head	entry; /* list of all controllers */
+};
+
+struct rdac_controller {
+	u8			subsys_id[SUBSYS_ID_LEN];
+	u8			slot_id[SLOT_ID_LEN];
+	int			use_10_ms;
+	struct kref		kref;
+	struct list_head	node; /* list of all controllers */
+	spinlock_t		lock;
+	int			submitted;
+	struct list_head	cmd_list; /* list of commands to be submitted */
+};
+
+struct c8_inquiry {
+	u8	peripheral_info;
+	u8	page_code; /* 0xC8 */
+	u8	reserved1;
+	u8	page_len;
+	u8	page_id[4]; /* "edid" */
+	u8	reserved2[3];
+	u8	vol_uniq_id_len;
+	u8	vol_uniq_id[16];
+	u8	vol_user_label_len;
+	u8	vol_user_label[60];
+	u8	array_uniq_id_len;
+	u8	array_unique_id[16];
+	u8	array_user_label_len;
+	u8	array_user_label[60];
+	u8	lun[8];
+};
+
+struct c2_inquiry {
+	u8	peripheral_info;
+	u8	page_code;	/* 0xC2 */
+	u8	reserved1;
+	u8	page_len;
+	u8	page_id[4];	/* "swr4" */
+	u8	sw_version[3];
+	u8	sw_date[3];
+	u8	features_enabled;
+	u8	max_lun_supported;
+	u8	partitions[239]; /* Total allocation length should be 0xFF */
+};
+
+static LIST_HEAD(ctlr_list);
+static spinlock_t list_lock = SPIN_LOCK_UNLOCKED;
+
+static inline void free_bio(struct bio *bio)
+{
+	__free_page(bio->bi_io_vec[0].bv_page);
+	bio_put(bio);
+}
+
+static void submit_inquiry(struct rdac_handler *, struct dm_path *, int,
+		unsigned, bio_end_io_t);
+static int c9_inquiry_endio(struct bio *, unsigned, int);
+#define submit_c9_inquiry(h, path) \
+	submit_inquiry(h, path, 0xC9, sizeof(struct c9_inquiry), \
+				c9_inquiry_endio)
+#define submit_c4_inquiry(h, path) \
+	submit_inquiry(h, path, 0xC4, sizeof(struct c4_inquiry), \
+				c4_inquiry_endio)
+
+#define submit_c8_inquiry(h, path) \
+	submit_inquiry(h, path, 0xC8, sizeof(struct c8_inquiry), \
+				c8_inquiry_endio)
+#define submit_c2_inquiry(h, path) \
+	submit_inquiry(h, path, 0xC2, sizeof(struct c2_inquiry), \
+				c2_inquiry_endio)
+
+static inline int had_failures(struct request *req, int error)
+{
+	return (error || host_byte(req->errors) != DID_OK ||
+			msg_byte(req->errors) != COMMAND_COMPLETE);
+}
+
+static void rdac_resubmit_all(struct rdac_handler *h)
+{
+	struct rdac_private *tmp, *p;
+	struct rdac_controller *ctlr = h->ctlr;
+
+	spin_lock(&ctlr->lock);
+	list_for_each_entry_safe(p, tmp, &ctlr->cmd_list, entry) {
+		submit_c9_inquiry(p->h, p->path);
+		list_del(&p->entry);
+		kfree(p);
+	}
+	ctlr->submitted = 0;
+	spin_unlock(&ctlr->lock);
+}
+
+static int mode_select_endio(struct bio *bio, unsigned done, int error)
+{
+	struct rdac_private *p = bio->bi_private;
+	struct rdac_handler *h = p->h;
+	struct request *req = p->req;
+	struct dm_path *path = p->path;
+	struct scsi_sense_hdr sense_hdr;
+	int sense = 0, fail = 0;
+
+	kfree(p);
+	if (bio->bi_size)
+		return 1;
+
+	if (had_failures(req, error)) {
+		fail = 1;
+		goto failed;
+	}
+
+	if (status_byte(req->errors) == CHECK_CONDITION) {
+		scsi_normalize_sense(req->sense, SCSI_SENSE_BUFFERSIZE,
+				&sense_hdr);
+		sense = (sense_hdr.sense_key << 16) | (sense_hdr.asc << 8) |
+				sense_hdr.ascq;
+		/* If it is retryable failure, submit the c9 inquiry again */
+		if (sense == 0x59136 || sense == 0x68b02 || sense == 0xb8b02) {
+			/* 0x59136    - Command lock contention
+			 * 0x[6b]8b02 - Quiesense in progress or achieved
+			 */
+			submit_c9_inquiry(h, path);
+			goto done;
+		}
+		if (sense)
+			DMINFO("MODE_SELECT failed on %s with sense 0x%x",
+						path->dev->name, sense);
+ 	}
+failed:
+	if (fail || sense)
+		dm_pg_init_complete(path, MP_FAIL_PATH);
+	else
+		dm_pg_init_complete(path, 0);
+
+done:
+	rdac_resubmit_all(h);
+	/* request is freed in block layer */
+	free_bio(bio);
+	return 0;
+}
+
+static struct bio *get_rdac_bio(struct dm_path *path, unsigned data_size,
+		bio_end_io_t endio, int rw, struct rdac_handler *h)
+{
+	struct bio *bio;
+	struct page *page;
+	struct rdac_private *p;
+
+	bio = bio_alloc(GFP_ATOMIC, 1);
+	if (!bio)
+		return NULL;
+
+	if (rw == WRITE)
+		bio->bi_rw |= (1 << BIO_RW);
+	bio->bi_bdev = path->dev->bdev;
+	bio->bi_sector = 0;
+	bio->bi_end_io = endio;
+
+	p = kmalloc(sizeof(*p), GFP_ATOMIC);
+	if (!p)
+		goto bio;
+
+	p->path = path;
+	p->h = h;
+	bio->bi_private = p;
+	page = alloc_page(GFP_ATOMIC);
+	if (!page)
+		goto free_private;
+
+	if (bio_add_page(bio, page, data_size, 0) == data_size)
+		return bio;
+
+	__free_page(page);
+free_private:
+	kfree(p);
+bio:
+	bio_put(bio);
+	return NULL;
+}
+
+static struct request *get_rdac_req(struct rdac_handler *h,
+		struct bio *bio, struct dm_path *path, int rw)
+{
+	struct request *rq;
+	struct block_device *bdev = bio->bi_bdev;
+	struct request_queue *q = bdev_get_queue(bdev);
+
+	rq = blk_get_request(q, rw, GFP_ATOMIC);
+	if (!rq) {
+		DMINFO("get_failover_req: blk_get_request failed");
+		return NULL;
+	}
+
+	rq->bio = rq->biotail = bio;
+	blk_rq_bio_prep(q, rq, bio);
+
+	rq->rq_disk = bdev->bd_contains->bd_disk;
+
+	/* bio backed don't set data */
+	rq->buffer = rq->data = NULL;
+	/* rq data_len used for pc cmd's request_bufflen */
+	rq->data_len = bio->bi_size;
+
+	rq->sense = h->sense;
+	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
+	rq->sense_len = 0;
+
+	memset(&rq->cmd, 0, BLK_MAX_CDB);
+
+	rq->timeout = h->timeout;
+	rq->cmd_type = REQ_TYPE_BLOCK_PC;
+	rq->cmd_flags |= REQ_FAILFAST | REQ_NOMERGE;
+
+	return rq;
+}
+
+static struct request *rdac_failover_get(struct rdac_handler *h,
+					struct dm_path *path)
+{
+	struct bio *bio;
+	struct request *rq;
+	struct rdac_mode_common *common;
+	struct rdac_private *p;
+	unsigned data_size = h->ctlr->use_10_ms ?
+				sizeof(struct rdac_pg_expanded) :
+				sizeof(struct rdac_pg_legacy);
+
+	/* get bio backing */
+	if (data_size > PAGE_SIZE)
+		/* this should never happen */
+		return NULL;
+
+	bio = get_rdac_bio(path, data_size, mode_select_endio, WRITE, h);
+	if (!bio) {
+		DMERR("rdac_failover_get: no bio");
+		return NULL;
+	}
+
+	if (h->ctlr->use_10_ms) {
+		struct rdac_pg_expanded *rdac_pg;
+
+		rdac_pg = (struct rdac_pg_expanded *)bio_data(bio);
+		memset(rdac_pg, 0, data_size);
+		common = &rdac_pg->common;
+		rdac_pg->page_code = RDAC_PAGE_CODE_REDUNDANT_CONTROLLER + 0x40;
+		rdac_pg->subpage_code = 0x1;
+		rdac_pg->page_len[0] = 0x01;
+		rdac_pg->page_len[1] = 0x28;
+		rdac_pg->lun_table[h->lun] = 0x81;
+	} else {
+		struct rdac_pg_legacy *rdac_pg;
+
+		rdac_pg = (struct rdac_pg_legacy *)bio_data(bio);
+		memset(rdac_pg, 0, data_size);
+		common = &rdac_pg->common;
+		rdac_pg->page_code = RDAC_PAGE_CODE_REDUNDANT_CONTROLLER;
+		rdac_pg->page_len = 0x68;
+		rdac_pg->lun_table[h->lun] = 0x81;
+	}
+	common->rdac_mode[1] = RDAC_MODE_TRANSFER_SPECIFIED_LUNS;
+	common->quiescence_timeout = RDAC_QUIESCENCE_TIME;
+	common->rdac_options = RDAC_FORCED_QUIESENCE;
+
+	/* get request for block layer packet command */
+	rq = get_rdac_req(h, bio, path, WRITE);
+	if (!rq) {
+		DMERR("rdac_failover_get: no rq");
+		free_bio(bio);
+		return NULL;
+	}
+
+	/* Strore the request information in private */
+	p = bio->bi_private;
+	p->req = rq;
+
+	/* Prepare the command. */
+	if (h->ctlr->use_10_ms) {
+		rq->cmd[0] = MODE_SELECT_10;
+		rq->cmd[7] = data_size >> 8;
+		rq->cmd[8] = data_size & 0xff;
+	} else {
+		rq->cmd[0] = MODE_SELECT;
+		rq->cmd[4] = data_size;
+	}
+	rq->cmd_len = COMMAND_SIZE(rq->cmd[0]);
+
+	return rq;
+}
+
+static int submit_mode_select(struct rdac_handler *h,
+				struct dm_path *path)
+{
+	int ret = 1;
+	struct request *rq;
+	struct request_queue *q = bdev_get_queue(path->dev->bdev);
+
+	if (!q) {
+		DMINFO("submit_mode_select: no queue");
+		goto fail_path;
+	}
+
+	rq = rdac_failover_get(h, path);
+	if (!rq) {
+		DMERR("submit_mode_select: no rq");
+		goto fail_path;
+	}
+
+	DMINFO("queueing MODE_SELECT command on %s", path->dev->name);
+
+	elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 1);
+	ret = 0;
+fail_path:
+	return ret;
+}
+
+static void release_ctlr(struct kref *kref)
+{
+	struct rdac_controller *ctlr;
+	ctlr = container_of(kref, struct rdac_controller, kref);
+
+	spin_lock(&list_lock);
+	list_del(&ctlr->node);
+	spin_unlock(&list_lock);
+	kfree(ctlr);
+}
+
+static struct rdac_controller *get_controller(u8 *subsys_id, u8 *slot_id)
+{
+	struct rdac_controller *ctlr, *tmp;
+
+	spin_lock(&list_lock);
+
+	list_for_each_entry(tmp, &ctlr_list, node) {
+		if ((memcmp(tmp->subsys_id, subsys_id, SUBSYS_ID_LEN) == 0) &&
+			  (memcmp(tmp->slot_id, slot_id, SLOT_ID_LEN) == 0)) {
+			kref_get(&tmp->kref);
+			spin_unlock(&list_lock);
+			return tmp;
+		}
+	}
+	ctlr = kmalloc(sizeof(*ctlr), GFP_ATOMIC);
+	if (!ctlr)
+		goto done;
+
+	/* initialize fields of controller */
+	memcpy(ctlr->subsys_id, subsys_id, SUBSYS_ID_LEN);
+	memcpy(ctlr->slot_id, slot_id, SLOT_ID_LEN);
+	kref_init(&ctlr->kref);
+	spin_lock_init(&ctlr->lock);
+	ctlr->submitted = 0;
+	ctlr->use_10_ms = -1;
+	INIT_LIST_HEAD(&ctlr->cmd_list);
+	list_add(&ctlr->node, &ctlr_list);
+done:
+	spin_unlock(&list_lock);
+	return ctlr;
+}
+
+static int c4_inquiry_endio(struct bio *bio, unsigned done, int error)
+{
+	struct rdac_private *p = bio->bi_private;
+	struct rdac_handler *h = p->h;
+	struct request *req = p->req;
+	struct dm_path *path = p->path;
+	struct c4_inquiry *sp;
+
+	kfree(p);
+	if (had_failures(req, error)) {
+		dm_pg_init_complete(path, MP_FAIL_PATH);
+		goto done;
+	}
+
+	sp = (struct c4_inquiry *)bio_data(bio);
+
+	h->ctlr = get_controller(sp->subsys_id, sp->slot_id);
+
+	if (h->ctlr)
+		submit_c9_inquiry(h, path);
+	else
+		dm_pg_init_complete(path, MP_FAIL_PATH);
+
+done:
+	/* request is freed in block layer */
+	free_bio(bio);
+	return 0;
+}
+
+static int c2_inquiry_endio(struct bio *bio, unsigned done, int error)
+{
+	struct rdac_private *p = bio->bi_private;
+	struct rdac_handler *h = p->h;
+	struct request *req = p->req;
+	struct dm_path *path = p->path;
+	struct c2_inquiry *sp;
+
+	if (had_failures(req, error)) {
+		dm_pg_init_complete(path, MP_FAIL_PATH);
+		goto done;
+	}
+
+	spin_lock(&h->ctlr->lock);
+	if (h->ctlr->use_10_ms != -1) { /* We lost the race, restart */
+		submit_c9_inquiry(h, path);
+		goto done_lock;
+	}
+	sp = (struct c2_inquiry *)bio_data(bio);
+
+	/* If more than MODE6_MAX_LUN luns are supported, use mode select 10 */
+	if (sp->max_lun_supported >= MODE6_MAX_LUN)
+		h->ctlr->use_10_ms = 1;
+	else
+		h->ctlr->use_10_ms = 0;
+
+	if (submit_mode_select(h, path) != 0)
+		dm_pg_init_complete(path, MP_FAIL_PATH);
+	else
+		h->ctlr->submitted = 1;
+
+done_lock:
+	spin_unlock(&h->ctlr->lock);
+done:
+	kfree(p);
+	/* request is freed in block layer */
+	free_bio(bio);
+	return 0;
+}
+
+static int c9_inquiry_endio(struct bio *bio, unsigned done, int error)
+{
+	struct rdac_private *p = bio->bi_private;
+	struct rdac_handler *h = p->h;
+	struct request *req = p->req;
+	struct dm_path *path = p->path;
+	struct c9_inquiry *sp;
+
+	if (had_failures(req, error)) {
+		dm_pg_init_complete(path, MP_FAIL_PATH);
+		goto done;
+	}
+
+	/* We need to look at the sense keys here to take clear action.
+	 * For now simple logic: If the host is in AVT mode or if controller
+	 * owns the lun, return dm_pg_init_complete(), otherwise submit
+	 * MODE SELECT.
+	 */
+	sp = (struct c9_inquiry *)bio_data(bio);
+
+	/* If in AVT mode, return success */
+	if ((sp->avte_cvp >> 7) == 0x1) {
+		dm_pg_init_complete(path, 0);
+		goto done;
+	}
+
+	/* If the controller on this path owns the LUN, return success */
+	if (sp->avte_cvp & 0x1) {
+		dm_pg_init_complete(path, 0);
+		goto done;
+	}
+
+	if (!h->ctlr)
+		submit_c4_inquiry(h, path);
+	else {
+		spin_lock(&h->ctlr->lock);
+		if (h->ctlr->use_10_ms == -1) {
+			submit_c2_inquiry(h, path);
+			spin_unlock(&h->ctlr->lock);
+			goto done;
+		}
+		if (!h->ctlr->submitted) {
+			if (submit_mode_select(h, path) != 0)
+				dm_pg_init_complete(path, MP_FAIL_PATH);
+			else
+				h->ctlr->submitted = 1;
+		} else {
+			list_add(&p->entry, &h->ctlr->cmd_list);
+			p = NULL; /* Reuse p, do not free */
+		}
+		spin_unlock(&h->ctlr->lock);
+	}
+
+done:
+	kfree(p);
+	/* request is freed in block layer */
+	free_bio(bio);
+	return 0;
+}
+
+static int c8_inquiry_endio(struct bio *bio, unsigned done, int error)
+{
+	struct rdac_private *p = bio->bi_private;
+	struct rdac_handler *h = p->h;
+	struct request *req = p->req;
+	struct dm_path *path = p->path;
+	struct c8_inquiry *sp;
+
+	kfree(p);
+	if (had_failures(req, error)) {
+		dm_pg_init_complete(path, MP_FAIL_PATH);
+		goto done;
+	}
+
+	/* We need to look at the sense keys here to take clear action.
+	 * For now simple logic: Get the lun from the inquiry page.
+	 */
+	sp = (struct c8_inquiry *)bio_data(bio);
+	h->lun = sp->lun[7]; /* currently it uses only one byte */
+	submit_c9_inquiry(h, path);
+
+done:
+	/* request is freed in block layer */
+	free_bio(bio);
+	return 0;
+}
+
+static struct request *rdac_inquiry_get(struct rdac_handler *h,
+		struct dm_path *path, int page_code,
+		unsigned len, bio_end_io_t endio)
+{
+	struct bio *bio;
+	struct request *rq;
+	struct rdac_private *p;
+
+	bio = get_rdac_bio(path, len, endio, READ, h);
+	if (!bio) {
+		DMERR("rdac_inquiry_get: no bio");
+		return NULL;
+	}
+	memset(bio_data(bio), 0, len);
+
+	/* get request for block layer packet command */
+	rq = get_rdac_req(h, bio, path, READ);
+	if (!rq) {
+		DMERR("rdac_inquiry_get: no rq");
+		free_bio(bio);
+		return NULL;
+	}
+
+	/* Strore the request information in private */
+	p = bio->bi_private;
+	p->req = rq;
+
+	/* Prepare the command. */
+	rq->cmd[0] = INQUIRY;
+	rq->cmd[1] = 1;
+	rq->cmd[2] = page_code;
+	rq->cmd[4] = len;
+	rq->cmd_len = COMMAND_SIZE(INQUIRY);
+	return rq;
+}
+
+/*
+ * only support subpage2c until we confirm that this is just a matter of
+ * of updating firmware or not, and RDAC (basic AVT works already) for now
+ * but we can add these in in when we get time and testers
+ */
+static int rdac_create(struct hw_handler *hwh, unsigned argc, char **argv)
+{
+	struct rdac_handler *h;
+	unsigned timeout = RDAC_FAILOVER_TIMEOUT;
+
+	if (argc > 1) {
+		DMWARN("only one argument (timeout) permitted");
+		return -EINVAL;
+	}
+
+	if ((argc == 1) && sscanf(argv[1], "%u", &timeout) != 1) {
+		DMWARN("invalid timeout value");
+		return -EINVAL;
+	}
+
+	h = kzalloc(sizeof(*h), GFP_KERNEL);
+	if (!h)
+		return -ENOMEM;
+
+	hwh->context = h;
+	h->timeout = timeout;
+	h->lun = UNINITIALIZED_LUN;
+	DMWARN("using RDAC command with timeout %u", h->timeout);
+
+	return 0;
+}
+
+static void rdac_destroy(struct hw_handler *hwh)
+{
+	struct rdac_handler *h = (struct rdac_handler *) hwh->context;
+
+	if (h->ctlr)
+		kref_put(&h->ctlr->kref, release_ctlr);
+	kfree(h);
+	hwh->context = NULL;
+}
+
+static unsigned rdac_error(struct hw_handler *hwh, struct bio *bio)
+{
+	/* Try default handler */
+	return dm_scsi_err_handler(hwh, bio);
+}
+
+static void submit_inquiry(struct rdac_handler *h,
+		struct dm_path *path, int page_code,
+		unsigned len, bio_end_io_t endio)
+{
+	struct request *rq;
+	struct request_queue *q = bdev_get_queue(path->dev->bdev);
+
+	if (!q)
+		goto fail_path;
+
+	rq = rdac_inquiry_get(h, path, page_code, len, endio);
+	if (!rq)
+		goto fail_path;
+
+	elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 1);
+	return;
+
+fail_path:
+	dm_pg_init_complete(path, MP_FAIL_PATH);
+}
+
+static void rdac_pg_init(struct hw_handler *hwh, unsigned bypassed,
+			struct dm_path *path)
+{
+	struct rdac_handler *h = hwh->context;
+
+	switch (h->lun) {
+	case UNINITIALIZED_LUN:
+		submit_c8_inquiry(h, path);
+		break;
+	default:
+		submit_c9_inquiry(h, path);
+	}
+}
+
+static struct hw_handler_type rdac_handler = {
+	.name = RDAC_DM_HWH_NAME,
+	.module = THIS_MODULE,
+	.create = rdac_create,
+	.destroy = rdac_destroy,
+	.pg_init = rdac_pg_init,
+	.error = rdac_error,
+};
+
+static int __init rdac_init(void)
+{
+	int r = dm_register_hw_handler(&rdac_handler);
+
+	if (r < 0)
+		DMERR("%s: register failed %d", RDAC_DM_HWH_NAME, r);
+
+	DMINFO("%s: version %s loaded", RDAC_DM_HWH_NAME, RDAC_DM_HWH_VER);
+
+	return r;
+}
+
+static void __exit rdac_exit(void)
+{
+	int r = dm_unregister_hw_handler(&rdac_handler);
+
+	if (r < 0)
+		DMERR("%s: unregister failed %d", RDAC_DM_HWH_NAME, r);
+}
+
+module_init(rdac_init);
+module_exit(rdac_exit);
+
+MODULE_DESCRIPTION("DM Multipath LSI/Engenio RDAC support");
+MODULE_AUTHOR("Mike Christie, Chandra Seetharaman");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(RDAC_DM_HWH_VER);