nvme-fabrics: Add FC LLDD loopback driver to test FC-NVME

Add FC LLDD loopback driver to test FC host and target transport within
nvme-fabrics

To aid in the development and testing of the lower-level api of the FC
transport, this loopback driver has been created to act as if it were a
FC hba driver supporting both the host interfaces as well as the target
interfaces with the nvme FC transport.

Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Jay Freyensee <james_p_freyensee@linux.intel.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

MAINTAINERS

@@ -8667,6 +8667,7 @@ F:	include/linux/nvme-fc.h
 F:	include/linux/nvme-fc-driver.h
 F:	drivers/nvme/host/fc.c
 F:	drivers/nvme/target/fc.c
+F:	drivers/nvme/target/fcloop.c
 
 NVMEM FRAMEWORK
 M:	Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

drivers/nvme/target/Kconfig

@@ -45,3 +45,16 @@ config NVME_TARGET_FC
 
 	  If unsure, say N.
 
+config NVME_TARGET_FCLOOP
+	tristate "NVMe over Fabrics FC Transport Loopback Test driver"
+	depends on NVME_TARGET
+	select NVME_CORE
+	select NVME_FABRICS
+	select SG_POOL
+	depends on NVME_FC
+	depends on NVME_TARGET_FC
+	help
+	  This enables the NVMe FC loopback test support, which can be useful
+	  to test NVMe-FC transport interfaces.
+
+	  If unsure, say N.

drivers/nvme/target/Makefile

@@ -3,9 +3,11 @@ obj-$(CONFIG_NVME_TARGET)		+= nvmet.o
 obj-$(CONFIG_NVME_TARGET_LOOP)		+= nvme-loop.o
 obj-$(CONFIG_NVME_TARGET_RDMA)		+= nvmet-rdma.o
 obj-$(CONFIG_NVME_TARGET_FC)		+= nvmet-fc.o
+obj-$(CONFIG_NVME_TARGET_FCLOOP)	+= nvme-fcloop.o
 
 nvmet-y		+= core.o configfs.o admin-cmd.o io-cmd.o fabrics-cmd.o \
 			discovery.o
 nvme-loop-y	+= loop.o
 nvmet-rdma-y	+= rdma.o
 nvmet-fc-y	+= fc.o
+nvme-fcloop-y	+= fcloop.o