[libata] improve device scan

Replace SCSI's legacy "bang at the door" method of probing with one
directly controlled by the underlying ATA transport layer.

We now only call scsi_scan_target() for devices we find, rather than
probing every possible channel/id within a certain range.

drivers/scsi/libata-core.c

@@ -4113,7 +4113,7 @@ int ata_device_add(struct ata_probe_ent *ent)
 	for (i = 0; i < count; i++) {
 		struct ata_port *ap = host_set->ports[i];
 
-		scsi_scan_host(ap->host);
+		ata_scsi_scan_host(ap);
 	}
 
 	dev_set_drvdata(dev, host_set);

drivers/scsi/libata-scsi.c

@@ -1678,3 +1678,15 @@ void ata_scsi_simulate(u16 *id,
 	}
 }
 
+void ata_scsi_scan_host(struct ata_port *ap)
+{
+	unsigned int i;
+
+	if (ap->flags & ATA_FLAG_PORT_DISABLED)
+		return;
+
+	for (i = 0; i < ATA_MAX_DEVICES; i++)
+		if (ata_dev_present(&ap->device[i]))
+			scsi_scan_target(&ap->host->shost_gendev, 0, i, ~0, 0);
+}
+

drivers/scsi/libata.h

@@ -51,6 +51,7 @@ extern void swap_buf_le16(u16 *buf, unsigned int buf_words);
 
 
 /* libata-scsi.c */
+extern void ata_scsi_scan_host(struct ata_port *ap);
 extern void ata_to_sense_error(struct ata_queued_cmd *qc, u8 drv_stat);
 extern int ata_scsi_error(struct Scsi_Host *host);
 extern unsigned int ata_scsiop_inq_std(struct ata_scsi_args *args, u8 *rbuf,