target: simplify backend driver registration

Rewrite the backend driver registration based on what we did to the fabric
drivers:  introduce a read-only struct target_bakckend_ops that the driver
registers, which is then instanciate as a struct target_backend by the
core.  This allows the ops vector to be smaller and allows us to mark it
const.  At the same time the registration function can set up the
configfs attributes, avoiding the need to add additional boilerplate code
for that to the drivers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

2 files changed, 6 insertions, 20 deletions

diff --git a/include/target/target_core_backend.h b/include/target/target_core_backend.h
index 80d9e486e33e..514b52019380 100644
--- a/include/target/target_core_backend.h
+++ b/include/target/target_core_backend.h
@@ -3,18 +3,7 @@
 
 #define TRANSPORT_FLAG_PASSTHROUGH              1
 
-struct target_backend_cits {
-        struct config_item_type tb_dev_cit;
-        struct config_item_type tb_dev_attrib_cit;
-        struct config_item_type tb_dev_pr_cit;
-        struct config_item_type tb_dev_wwn_cit;
-        struct config_item_type tb_dev_alua_tg_pt_gps_cit;
-        struct config_item_type tb_dev_stat_cit;
-};
-
-struct se_subsystem_api {
-        struct list_head sub_api_list;
-
+struct target_backend_ops {
         char name[16];
         char inquiry_prod[16];
         char inquiry_rev[4];
@@ -52,7 +41,7 @@ struct se_subsystem_api {
         int (*format_prot)(struct se_device *);
         void (*free_prot)(struct se_device *);
 
-        struct target_backend_cits tb_cits;
+        struct configfs_attribute **tb_dev_attrib_attrs;
 };
 
 struct sbc_ops {
@@ -64,8 +53,8 @@ struct sbc_ops {
         sense_reason_t (*execute_unmap)(struct se_cmd *cmd);
 };
 
-int     transport_subsystem_register(struct se_subsystem_api *);
-void    transport_subsystem_release(struct se_subsystem_api *);
+int     transport_backend_register(const struct target_backend_ops *);
+void    target_backend_unregister(const struct target_backend_ops *);
 
 void    target_complete_cmd(struct se_cmd *, u8);
 void    target_complete_cmd_with_length(struct se_cmd *, u8, int);
@@ -103,9 +92,6 @@ sense_reason_t	transport_generic_map_mem_to_cmd(struct se_cmd *,
 
 bool    target_lun_is_rdonly(struct se_cmd *);
 
-/* From target_core_configfs.c to setup default backend config_item_types */
-void    target_core_setup_sub_cits(struct se_subsystem_api *);
-
 /* attribute helpers from target_core_device.c for backend drivers */
 bool    se_dev_check_wce(struct se_device *);
 int     se_dev_set_max_unmap_lba_count(struct se_device *, u32);
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 78ed2a83838c..03e2ee8f8337 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -797,7 +797,7 @@ struct se_device {
 #define SE_UDEV_PATH_LEN 512            /* must be less than PAGE_SIZE */
         unsigned char           udev_path[SE_UDEV_PATH_LEN];
         /* Pointer to template of function pointers for transport */
-        struct se_subsystem_api *transport;
+        const struct target_backend_ops *transport;
         /* Linked list for struct se_hba struct se_device list */
         struct list_head        dev_list;
         struct se_lun           xcopy_lun;
@@ -819,7 +819,7 @@ struct se_hba {
         spinlock_t              device_lock;
         struct config_group     hba_group;
         struct mutex            hba_access_mutex;
-        struct se_subsystem_api *transport;
+        struct target_backend   *backend;
 };
 
 struct scsi_port_stats {