target: add a parse_cdb method to the backend drivers

Instead of trying to handle all SCSI command sets in one function
(transport_generic_cmd_sequencer) call out to the backend driver to perform
this functionality.  For pSCSI a copy of the existing code is used, but for
all virtual backends we can use a new parse_sbc_cdb helper is used to
provide a simple SBC emulation.

For now this setups means a fair amount of duplication between pSCSI and the
SBC library, but patches later in this series will sort out that problem.

(nab: Fix up build failure in target_core_pscsi.c)
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/Makefile

@@ -10,6 +10,7 @@ target_core_mod-y		:= target_core_configfs.o \
 				   target_core_tpg.o \
 				   target_core_transport.o \
 				   target_core_cdb.o \
+				   target_core_sbc.o \
 				   target_core_spc.o \
 				   target_core_ua.o \
 				   target_core_rd.o \

drivers/target/target_core_file.c

@@ -561,6 +561,7 @@ static struct se_subsystem_api fileio_template = {
 	.allocate_virtdevice	= fd_allocate_virtdevice,
 	.create_virtdevice	= fd_create_virtdevice,
 	.free_device		= fd_free_device,
+	.parse_cdb		= sbc_parse_cdb,
 	.execute_cmd		= fd_execute_cmd,
 	.do_sync_cache		= fd_emulate_sync_cache,
 	.check_configfs_dev_params = fd_check_configfs_dev_params,

drivers/target/target_core_iblock.c

@@ -653,6 +653,7 @@ static struct se_subsystem_api iblock_template = {
 	.allocate_virtdevice	= iblock_allocate_virtdevice,
 	.create_virtdevice	= iblock_create_virtdevice,
 	.free_device		= iblock_free_device,
+	.parse_cdb		= sbc_parse_cdb,
 	.execute_cmd		= iblock_execute_cmd,
 	.do_discard		= iblock_do_discard,
 	.do_sync_cache		= iblock_emulate_sync_cache,

drivers/target/target_core_internal.h

@@ -96,9 +96,6 @@ int	core_tpg_post_addlun(struct se_portal_group *, struct se_lun *,
 struct se_lun *core_tpg_pre_dellun(struct se_portal_group *, u32 unpacked_lun);
 int	core_tpg_post_dellun(struct se_portal_group *, struct se_lun *);
 
-/* target_core_spc.c */
-int	spc_parse_cdb(struct se_cmd *cmd, unsigned int *size, bool passthrough);
-
 /* target_core_transport.c */
 extern struct kmem_cache *se_tmr_req_cache;
 

drivers/target/target_core_rd.c

@@ -468,6 +468,7 @@ static struct se_subsystem_api rd_mcp_template = {
 	.allocate_virtdevice	= rd_allocate_virtdevice,
 	.create_virtdevice	= rd_create_virtdevice,
 	.free_device		= rd_free_device,
+	.parse_cdb		= sbc_parse_cdb,
 	.execute_cmd		= rd_execute_cmd,
 	.check_configfs_dev_params = rd_check_configfs_dev_params,
 	.set_configfs_dev_params = rd_set_configfs_dev_params,

drivers/target/target_core_spc.c

@@ -152,6 +152,7 @@ int spc_parse_cdb(struct se_cmd *cmd, unsigned int *size, bool passthrough)
 			cmd->sam_task_attr = MSG_HEAD_TAG;
 		break;
 	case TEST_UNIT_READY:
+		*size = 0;
 		if (!passthrough)
 			cmd->execute_cmd = target_emulate_noop;
 		break;

include/target/target_core_backend.h

@@ -24,6 +24,8 @@ struct se_subsystem_api {
 				struct se_subsystem_dev *, void *);
 	void (*free_device)(void *);
 	int (*transport_complete)(struct se_cmd *cmd, struct scatterlist *);
+
+	int (*parse_cdb)(struct se_cmd *cmd, unsigned int *size);
 	int (*execute_cmd)(struct se_cmd *, struct scatterlist *, u32,
 			enum dma_data_direction);
 	int (*do_discard)(struct se_device *, sector_t, u32);
@@ -49,6 +51,9 @@ struct se_device *transport_add_device_to_core_hba(struct se_hba *,
 
 void	target_complete_cmd(struct se_cmd *, u8);
 
+int	sbc_parse_cdb(struct se_cmd *cmd, unsigned int *size);
+int	spc_parse_cdb(struct se_cmd *cmd, unsigned int *size, bool passthrough);
+
 void	transport_set_vpd_proto_id(struct t10_vpd *, unsigned char *);
 int	transport_set_vpd_assoc(struct t10_vpd *, unsigned char *);
 int	transport_set_vpd_ident_type(struct t10_vpd *, unsigned char *);