[SCSI] scsi_dh: add infrastructure for SCSI Device Handlers
Some of the storage devices (that can be accessed through multiple paths),
do need some special handling for
1. Activating the passive path of the storage access.
2. Decode and handle the special sense codes returned by the devices.
3. Handle the I/Os being sent to the passive path, especially
during the device probe time.
when accessed through multiple paths.
As of today this special device handling is done at the dm-multipath
layer using dm-handlers. That works well for (1); for (2) to be handled
at dm layer, scsi sense information need to be exported from SCSI to dm-layer,
which is not very attractive; (3) cannot be done at all at the dm layer.
Device handler has been moved to SCSI mainly to handle (2) and (3) properly.
Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/drivers/scsi/Makefile b/drivers/scsi/Makefile
index 6c775e3..aa8272e 100644
--- a/drivers/scsi/Makefile
+++ b/drivers/scsi/Makefile
@@ -34,6 +34,7 @@
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