[SCSI] libsas: Add a sysfs knob to enable/disable a phy

This patch lets a user arbitrarily enable or disable a phy via sysfs.
Potential applications include shutting down a phy to replace one
lane of wide port, and (more importantly) providing a method for the
libata SATL to control the phy.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/include/scsi/scsi_transport_sas.h b/include/scsi/scsi_transport_sas.h
index 59633a82d..45d5859 100644
--- a/include/scsi/scsi_transport_sas.h
+++ b/include/scsi/scsi_transport_sas.h
@@ -54,6 +54,7 @@
 struct sas_phy {
 	struct device		dev;
 	int			number;
+	int			enabled;
 
 	/* phy identification */
 	struct sas_identify	identify;
@@ -163,6 +164,7 @@
 	int (*get_enclosure_identifier)(struct sas_rphy *, u64 *);
 	int (*get_bay_identifier)(struct sas_rphy *);
 	int (*phy_reset)(struct sas_phy *, int);
+	int (*phy_enable)(struct sas_phy *, int);
 	int (*set_phy_speed)(struct sas_phy *, struct sas_phy_linkrates *);
 };