[SCSI] aacraid: Changeable queue depth

Inspired by Brian King's patch to the ibmvscsi driver. Adds support for
a changeable queue depth to the aacraid driver.
Signed-off-by: Mark Salyzyn <aacraid@adaptec.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/aacraid/linit.c

@@ -446,6 +446,43 @@ static int aac_slave_configure(struct scsi_device *sdev)
 	return 0;
 }
 
+/**
+ *	aac_change_queue_depth		-	alter queue depths
+ *	@sdev:	SCSI device we are considering
+ *	@depth:	desired queue depth
+ *
+ *	Alters queue depths for target device based on the host adapter's
+ *	total capacity and the queue depth supported by the target device.
+ */
+
+static int aac_change_queue_depth(struct scsi_device *sdev, int depth)
+{
+	if (sdev->tagged_supported && (sdev->type == TYPE_DISK) &&
+	    (sdev_channel(sdev) == CONTAINER_CHANNEL)) {
+		struct scsi_device * dev;
+		struct Scsi_Host *host = sdev->host;
+		unsigned num = 0;
+
+		__shost_for_each_device(dev, host) {
+			if (dev->tagged_supported && (dev->type == TYPE_DISK) &&
+			    (sdev_channel(dev) == CONTAINER_CHANNEL))
+				++num;
+			++num;
+		}
+		if (num >= host->can_queue)
+			num = host->can_queue - 1;
+		if (depth > (host->can_queue - num))
+			depth = host->can_queue - num;
+		if (depth > 256)
+			depth = 256;
+		else if (depth < 2)
+			depth = 2;
+		scsi_adjust_queue_depth(sdev, MSG_ORDERED_TAG, depth);
+	} else
+		scsi_adjust_queue_depth(sdev, 0, 1);
+	return sdev->queue_depth;
+}
+
 static int aac_ioctl(struct scsi_device *sdev, int cmd, void __user * arg)
 {
 	struct aac_dev *dev = (struct aac_dev *)sdev->host->hostdata;
@@ -844,6 +881,7 @@ static struct scsi_host_template aac_driver_template = {
 	.bios_param     		= aac_biosparm,	
 	.shost_attrs			= aac_attrs,
 	.slave_configure		= aac_slave_configure,
+	.change_queue_depth		= aac_change_queue_depth,
 	.eh_abort_handler		= aac_eh_abort,
 	.eh_host_reset_handler		= aac_eh_reset,
 	.can_queue      		= AAC_NUM_IO_FIB,