[SCSI] scsi tgt: scsi target lib functionality

The core scsi target lib functions.

TODO:
- mv md/dm-bio-list.h to linux/bio-list.h so md and us do not have to
do that weird include.
- convert scsi_tgt_cmd's work struct to James's execute code. And try
to kill our scsi_tgt_cmd.
- add host state checking. We do refcouting so hotplug is partially
supported, but we need to add state checking to make it easier on
the LLD.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/scsi_tgt_priv.h

+struct scsi_cmnd;
+struct scsi_lun;
+struct Scsi_Host;
+struct task_struct;
+
+/* tmp - will replace with SCSI logging stuff */
+#define eprintk(fmt, args...)					\
+do {								\
+	printk("%s(%d) " fmt, __FUNCTION__, __LINE__, ##args);	\
+} while (0)
+
+#define dprintk(fmt, args...)
+/* #define dprintk eprintk */
+
+extern void scsi_tgt_if_exit(void);
+extern int scsi_tgt_if_init(void);
+
+extern int scsi_tgt_uspace_send_cmd(struct scsi_cmnd *cmd, struct scsi_lun *lun,
+				    u64 tag);
+extern int scsi_tgt_uspace_send_status(struct scsi_cmnd *cmd, u64 tag);
+extern int scsi_tgt_kspace_exec(int host_no, u64 tag, int result, u32 len,
+				unsigned long uaddr, u8 rw);
+extern int scsi_tgt_uspace_send_tsk_mgmt(int host_no, int function, u64 tag,
+					 struct scsi_lun *scsilun, void *data);
+extern int scsi_tgt_kspace_tsk_mgmt(int host_no, u64 mid, int result);

include/scsi/scsi_tgt.h

+/*
+ * SCSI target definitions
+ */
+
+#include <linux/dma-mapping.h>
+
+struct Scsi_Host;
+struct scsi_cmnd;
+struct scsi_lun;
+
+extern struct Scsi_Host *scsi_tgt_cmd_to_host(struct scsi_cmnd *);
+extern int scsi_tgt_alloc_queue(struct Scsi_Host *);
+extern void scsi_tgt_free_queue(struct Scsi_Host *);
+extern int scsi_tgt_queue_command(struct scsi_cmnd *, struct scsi_lun *, u64);
+extern int scsi_tgt_tsk_mgmt_request(struct Scsi_Host *, int, u64, struct scsi_lun *,
+				     void *);
+extern struct scsi_cmnd *scsi_host_get_command(struct Scsi_Host *,
+					       enum dma_data_direction,	gfp_t);
+extern void scsi_host_put_command(struct Scsi_Host *, struct scsi_cmnd *);