8 files changed, 201 insertions, 0 deletions

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 81ccbd7f9e34..7886ec6e5f87 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -1771,4 +1771,6 @@ endif # SCSI_LOWLEVEL
 
 source "drivers/scsi/pcmcia/Kconfig"
 
+source "drivers/scsi/device_handler/Kconfig"
+
 endmenu
diff --git a/drivers/scsi/Makefile b/drivers/scsi/Makefile
index 6c775e350c98..aa8272e188ea 100644
--- a/drivers/scsi/Makefile
+++ b/drivers/scsi/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_SCSI_ISCSI_ATTRS)	+= scsi_transport_iscsi.o
 obj-$(CONFIG_SCSI_SAS_ATTRS)    += scsi_transport_sas.o
 obj-$(CONFIG_SCSI_SAS_LIBSAS)   += libsas/
 obj-$(CONFIG_SCSI_SRP_ATTRS)    += scsi_transport_srp.o
+obj-$(CONFIG_SCSI_DH)           += device_handler/
 
 obj-$(CONFIG_ISCSI_TCP)         += libiscsi.o   iscsi_tcp.o
 obj-$(CONFIG_INFINIBAND_ISER)   += libiscsi.o
diff --git a/drivers/scsi/device_handler/Kconfig b/drivers/scsi/device_handler/Kconfig
new file mode 100644
index 000000000000..228241d1d98c
--- /dev/null
+++ b/drivers/scsi/device_handler/Kconfig
@@ -0,0 +1,12 @@
+#
+# SCSI Device Handler configuration
+#
+
+menuconfig SCSI_DH
+        tristate "SCSI Device Handlers"
+        depends on SCSI
+        default n
+        help
+          SCSI Device Handlers provide device specific support for
+          devices utilized in multipath configurations. Say Y here to
+          select support for specific hardware.
diff --git a/drivers/scsi/device_handler/Makefile b/drivers/scsi/device_handler/Makefile
new file mode 100644
index 000000000000..f306e44e3837
--- /dev/null
+++ b/drivers/scsi/device_handler/Makefile
@@ -0,0 +1,4 @@
+#
+# SCSI Device Handler
+#
+obj-$(CONFIG_SCSI_DH)           += scsi_dh.o
diff --git a/drivers/scsi/device_handler/scsi_dh.c b/drivers/scsi/device_handler/scsi_dh.c
new file mode 100644
index 000000000000..ab6c21cd9689
--- /dev/null
+++ b/drivers/scsi/device_handler/scsi_dh.c
@@ -0,0 +1,162 @@
+/*
+ * SCSI device handler infrastruture.
+ *
+ * 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.
+ *
+ * Copyright IBM Corporation, 2007
+ *      Authors:
+ *               Chandra Seetharaman <sekharan@us.ibm.com>
+ *               Mike Anderson <andmike@linux.vnet.ibm.com>
+ */
+
+#include <scsi/scsi_dh.h>
+#include "../scsi_priv.h"
+
+static DEFINE_SPINLOCK(list_lock);
+static LIST_HEAD(scsi_dh_list);
+
+static struct scsi_device_handler *get_device_handler(const char *name)
+{
+        struct scsi_device_handler *tmp, *found = NULL;
+
+        spin_lock(&list_lock);
+        list_for_each_entry(tmp, &scsi_dh_list, list) {
+                if (!strcmp(tmp->name, name)) {
+                        found = tmp;
+                        break;
+                }
+        }
+        spin_unlock(&list_lock);
+        return found;
+}
+
+static int scsi_dh_notifier_add(struct device *dev, void *data)
+{
+        struct scsi_device_handler *scsi_dh = data;
+
+        scsi_dh->nb.notifier_call(&scsi_dh->nb, BUS_NOTIFY_ADD_DEVICE, dev);
+        return 0;
+}
+
+/*
+ * scsi_register_device_handler - register a device handler personality
+ *      module.
+ * @scsi_dh - device handler to be registered.
+ *
+ * Returns 0 on success, -EBUSY if handler already registered.
+ */
+int scsi_register_device_handler(struct scsi_device_handler *scsi_dh)
+{
+        int ret = -EBUSY;
+        struct scsi_device_handler *tmp;
+
+        tmp = get_device_handler(scsi_dh->name);
+        if (tmp)
+                goto done;
+
+        ret = bus_register_notifier(&scsi_bus_type, &scsi_dh->nb);
+
+        bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh, scsi_dh_notifier_add);
+        spin_lock(&list_lock);
+        list_add(&scsi_dh->list, &scsi_dh_list);
+        spin_unlock(&list_lock);
+
+done:
+        return ret;
+}
+EXPORT_SYMBOL_GPL(scsi_register_device_handler);
+
+static int scsi_dh_notifier_remove(struct device *dev, void *data)
+{
+        struct scsi_device_handler *scsi_dh = data;
+
+        scsi_dh->nb.notifier_call(&scsi_dh->nb, BUS_NOTIFY_DEL_DEVICE, dev);
+        return 0;
+}
+
+/*
+ * scsi_unregister_device_handler - register a device handler personality
+ *      module.
+ * @scsi_dh - device handler to be unregistered.
+ *
+ * Returns 0 on success, -ENODEV if handler not registered.
+ */
+int scsi_unregister_device_handler(struct scsi_device_handler *scsi_dh)
+{
+        int ret = -ENODEV;
+        struct scsi_device_handler *tmp;
+
+        tmp = get_device_handler(scsi_dh->name);
+        if (!tmp)
+                goto done;
+
+        ret = bus_unregister_notifier(&scsi_bus_type, &scsi_dh->nb);
+
+        bus_for_each_dev(&scsi_bus_type, NULL, scsi_dh,
+                                        scsi_dh_notifier_remove);
+        spin_lock(&list_lock);
+        list_del(&scsi_dh->list);
+        spin_unlock(&list_lock);
+
+done:
+        return ret;
+}
+EXPORT_SYMBOL_GPL(scsi_unregister_device_handler);
+
+/*
+ * scsi_dh_activate - activate the path associated with the scsi_device
+ *      corresponding to the given request queue.
+ * @q - Request queue that is associated with the scsi_device to be
+ *      activated.
+ */
+int scsi_dh_activate(struct request_queue *q)
+{
+        int err = 0;
+        unsigned long flags;
+        struct scsi_device *sdev;
+        struct scsi_device_handler *scsi_dh = NULL;
+
+        spin_lock_irqsave(q->queue_lock, flags);
+        sdev = q->queuedata;
+        if (sdev && sdev->scsi_dh_data)
+                scsi_dh = sdev->scsi_dh_data->scsi_dh;
+        if (!scsi_dh || !get_device(&sdev->sdev_gendev))
+                err = SCSI_DH_NOSYS;
+        spin_unlock_irqrestore(q->queue_lock, flags);
+
+        if (err)
+                return err;
+
+        if (scsi_dh->activate)
+                err = scsi_dh->activate(sdev);
+        put_device(&sdev->sdev_gendev);
+        return err;
+}
+EXPORT_SYMBOL_GPL(scsi_dh_activate);
+
+/*
+ * scsi_dh_handler_exist - Return TRUE(1) if a device handler exists for
+ *      the given name. FALSE(0) otherwise.
+ * @name - name of the device handler.
+ */
+int scsi_dh_handler_exist(const char *name)
+{
+        return (get_device_handler(name) != NULL);
+}
+EXPORT_SYMBOL_GPL(scsi_dh_handler_exist);
+
+MODULE_DESCRIPTION("SCSI device handler");
+MODULE_AUTHOR("Chandra Seetharaman <sekharan@us.ibm.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index eaf5a8add1ba..006a95916f72 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -298,6 +298,7 @@ static inline void scsi_eh_prt_fail_stats(struct Scsi_Host *shost,
  */
 static int scsi_check_sense(struct scsi_cmnd *scmd)
 {
+        struct scsi_device *sdev = scmd->device;
         struct scsi_sense_hdr sshdr;
 
         if (! scsi_command_normalize_sense(scmd, &sshdr))
@@ -306,6 +307,16 @@ static int scsi_check_sense(struct scsi_cmnd *scmd)
         if (scsi_sense_is_deferred(&sshdr))
                 return NEEDS_RETRY;
 
+        if (sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh &&
+                        sdev->scsi_dh_data->scsi_dh->check_sense) {
+                int rc;
+
+                rc = sdev->scsi_dh_data->scsi_dh->check_sense(sdev, &sshdr);
+                if (rc != SCSI_RETURN_NOT_HANDLED)
+                        return rc;
+                /* handler does not care. Drop down to default handling */
+        }
+
         /*
          * Previous logic looked for FILEMARK, EOM or ILI which are
          * mainly associated with tapes and returned SUCCESS.
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index a82d2fe80fb5..033c58a65f50 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1160,6 +1160,14 @@ int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
 
         if (ret != BLKPREP_OK)
                 return ret;
+
+        if (unlikely(sdev->scsi_dh_data && sdev->scsi_dh_data->scsi_dh
+                         && sdev->scsi_dh_data->scsi_dh->prep_fn)) {
+                ret = sdev->scsi_dh_data->scsi_dh->prep_fn(sdev, req);
+                if (ret != BLKPREP_OK)
+                        return ret;
+        }
+
         /*
          * Filesystem requests must transfer data.
          */
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 93d2b6714453..b6e561059779 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -439,6 +439,7 @@ struct bus_type scsi_bus_type = {
         .resume         = scsi_bus_resume,
         .remove         = scsi_bus_remove,
 };
+EXPORT_SYMBOL_GPL(scsi_bus_type);
 
 int scsi_sysfs_register(void)
 {