scsi: Add scsi_vpd_tpg_id()

Implement scsi_vpd_tpg_id() to extract the target
port group id and the relative port id from
SCSI VPD page 0x83.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

2 files changed, 49 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e352c2b7deaf..fa6b2c4eb7a2 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -23,6 +23,7 @@
 #include <linux/scatterlist.h>
 #include <linux/blk-mq.h>
 #include <linux/ratelimit.h>
+#include <asm/unaligned.h>
 
 #include <scsi/scsi.h>
 #include <scsi/scsi_cmnd.h>
@@ -3294,3 +3295,50 @@ next_desig:
         return id_size;
 }
 EXPORT_SYMBOL(scsi_vpd_lun_id);
+
+/*
+ * scsi_vpd_tpg_id - return a target port group identifier
+ * @sdev: SCSI device
+ *
+ * Returns the Target Port Group identifier from the information
+ * froom VPD page 0x83 of the device.
+ *
+ * Returns the identifier or error on failure.
+ */
+int scsi_vpd_tpg_id(struct scsi_device *sdev, int *rel_id)
+{
+        unsigned char *d;
+        unsigned char __rcu *vpd_pg83;
+        int group_id = -EAGAIN, rel_port = -1;
+
+        rcu_read_lock();
+        vpd_pg83 = rcu_dereference(sdev->vpd_pg83);
+        if (!vpd_pg83) {
+                rcu_read_unlock();
+                return -ENXIO;
+        }
+
+        d = sdev->vpd_pg83 + 4;
+        while (d < sdev->vpd_pg83 + sdev->vpd_pg83_len) {
+                switch (d[1] & 0xf) {
+                case 0x4:
+                        /* Relative target port */
+                        rel_port = get_unaligned_be16(&d[6]);
+                        break;
+                case 0x5:
+                        /* Target port group */
+                        group_id = get_unaligned_be16(&d[6]);
+                        break;
+                default:
+                        break;
+                }
+                d += d[3] + 4;
+        }
+        rcu_read_unlock();
+
+        if (group_id >= 0 && rel_id && rel_port != -1)
+                *rel_id = rel_port;
+
+        return group_id;
+}
+EXPORT_SYMBOL(scsi_vpd_tpg_id);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index 4c49cfa25cac..f63a16760ae9 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -416,6 +416,7 @@ static inline int scsi_execute_req(struct scsi_device *sdev,
 extern void sdev_disable_disk_events(struct scsi_device *sdev);
 extern void sdev_enable_disk_events(struct scsi_device *sdev);
 extern int scsi_vpd_lun_id(struct scsi_device *, char *, size_t);
+extern int scsi_vpd_tpg_id(struct scsi_device *, int *);
 
 #ifdef CONFIG_PM
 extern int scsi_autopm_get_device(struct scsi_device *);