[SCSI] scsi_dh: add the interface scsi_dh_set_params()

When we moved the device handler functionality from dm layer to SCSI layer
we dropped the parameter functionality.

This path adds an interface to scsi dh layer to set device handler
parameters.

Basically, multipath layer need to create a string with all the parameters
and call scsi_dh_set_params() after it called scsi_dh_attach() on a
device.

If a device handler provides such an interface it will handle the parameters
as it expects them.

Reported-by: Eddie Williams <Eddie.Williams@steeleye.com>
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Tested-by: Eddie Williams <Eddie.Williams@steeleye.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

2 files changed, 6 insertions, 0 deletions

diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 1f3a4c8044c0..9af48cbf0036 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -187,6 +187,7 @@ struct scsi_device_handler {
         void (*detach)(struct scsi_device *);
         int (*activate)(struct scsi_device *);
         int (*prep_fn)(struct scsi_device *, struct request *);
+        int (*set_params)(struct scsi_device *, const char *);
 };
 
 struct scsi_dh_data {
diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
index 33efce20c26c..ff2407405b42 100644
--- a/include/scsi/scsi_dh.h
+++ b/include/scsi/scsi_dh.h
@@ -60,6 +60,7 @@ extern int scsi_dh_activate(struct request_queue *);
 extern int scsi_dh_handler_exist(const char *);
 extern int scsi_dh_attach(struct request_queue *, const char *);
 extern void scsi_dh_detach(struct request_queue *);
+extern int scsi_dh_set_params(struct request_queue *, const char *);
 #else
 static inline int scsi_dh_activate(struct request_queue *req)
 {
@@ -77,4 +78,8 @@ static inline void scsi_dh_detach(struct request_queue *q)
 {
         return;
 }
+static inline int scsi_dh_set_params(struct request_queue *req, const char *params)
+{
+        return -SCSI_DH_NOSYS;
+}
 #endif