[SCSI] Make scsi_scan_host work for drivers which find their own targets

If a driver can find its own targets, it can now fill in scan_finished and
(optionally) scan_start in the scsi_host_template. Then, when it calls
scsi_scan_host(), it will be called back (from a thread if asynchronous
discovery is enabled), first to start the scan, and then at intervals to
check if the scan is completed.

Also make scsi_prep_async_scan and scsi_finish_async_scan static.

Signed-off-by: Matthew Wilcox <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/scsi_scan.c

···
  * that other asynchronous scans started after this one won't affect the
  * ordering of the discovered devices.
  */
-struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
+static struct async_scan_data *scsi_prep_async_scan(struct Scsi_Host *shost)
 {
 	struct async_scan_data *data;
 
···
  * This function announces all the devices it has found to the rest
  * of the system.
  */
-void scsi_finish_async_scan(struct async_scan_data *data)
+static void scsi_finish_async_scan(struct async_scan_data *data)
 {
 	struct Scsi_Host *shost;
 
···
 	kfree(data);
 }
 
+static void do_scsi_scan_host(struct Scsi_Host *shost)
+{
+	if (shost->hostt->scan_finished) {
+		unsigned long start = jiffies;
+		if (shost->hostt->scan_start)
+			shost->hostt->scan_start(shost);
+
+		while (!shost->hostt->scan_finished(shost, jiffies - start))
+			msleep(10);
+	} else {
+		scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD,
+				SCAN_WILD_CARD, 0);
+	}
+}
+
 static int do_scan_async(void *_data)
 {
 	struct async_scan_data *data = _data;
-	scsi_scan_host_selected(data->shost, SCAN_WILD_CARD, SCAN_WILD_CARD,
-				SCAN_WILD_CARD, 0);
-
+	do_scsi_scan_host(data->shost);
 	scsi_finish_async_scan(data);
 	return 0;
 }
···
 
 	data = scsi_prep_async_scan(shost);
 	if (!data) {
-		scsi_scan_host_selected(shost, SCAN_WILD_CARD, SCAN_WILD_CARD,
-					SCAN_WILD_CARD, 0);
+		do_scsi_scan_host(shost);
 		return;
 	}
+
 	kthread_run(do_scan_async, data, "scsi_scan_%d", shost->host_no);
 }
 EXPORT_SYMBOL(scsi_scan_host);

include/scsi/scsi_host.h

···
 	void (* target_destroy)(struct scsi_target *);
 
 	/*
+	 * If a host has the ability to discover targets on its own instead
+	 * of scanning the entire bus, it can fill in this function and
+	 * call scsi_scan_host().  This function will be called periodically
+	 * until it returns 1 with the scsi_host and the elapsed time of
+	 * the scan in jiffies.
+	 *
+	 * Status: OPTIONAL
+	 */
+	int (* scan_finished)(struct Scsi_Host *, unsigned long);
+
+	/*
+	 * If the host wants to be called before the scan starts, but
+	 * after the midlayer has set up ready for the scan, it can fill
+	 * in this function.
+	 */
+	void (* scan_start)(struct Scsi_Host *);
+
+	/*
 	 * fill in this function to allow the queue depth of this host
 	 * to be changeable (on a per device basis).  returns either
 	 * the current queue depth setting (may be different from what