Index: sys/dev/ata/ata-disk.c
===================================================================
RCS file: /home/ncvs/src/sys/dev/ata/ata-disk.c,v
retrieving revision 1.60.2.11
diff -u -r1.60.2.11 ata-disk.c
--- sys/dev/ata/ata-disk.c	2001/02/25 21:35:20	1.60.2.11
+++ sys/dev/ata/ata-disk.c	2001/03/30 18:23:15
@@ -99,6 +99,10 @@
 /* internal vars */
 static u_int32_t adp_lun_map = 0;
 static MALLOC_DEFINE(M_AD, "AD driver", "ATA disk driver");
+static int ata_dma, ata_wc, ata_tags; 
+TUNABLE_INT_DECL("hw.ata.ata_dma", 1, ata_dma);
+TUNABLE_INT_DECL("hw.ata.wc", 0, ata_wc);
+TUNABLE_INT_DECL("hw.ata.tags", 0, ata_tags);
 
 /* defines */
 #define	AD_MAX_RETRIES	3
@@ -152,21 +156,27 @@
 		    0, 0, 0, 0, ATA_C_F_ENAB_RCACHE, ATA_WAIT_INTR))
 	printf("ad%d: enabling readahead cache failed\n", adp->lun);
 
-#if defined(ATA_ENABLE_WC) || defined(ATA_ENABLE_TAGS)
-    if (ata_command(adp->controller, adp->unit, ATA_C_SETFEATURES,
-		    0, 0, 0, 0, ATA_C_F_ENAB_WCACHE, ATA_WAIT_INTR))
-	printf("ad%d: enabling write cache failed\n", adp->lun);
-#else
-    if (ata_command(adp->controller, adp->unit, ATA_C_SETFEATURES,
-		    0, 0, 0, 0, ATA_C_F_DIS_WCACHE, ATA_WAIT_INTR))
-	printf("ad%d: disabling write cache failed\n", adp->lun);
-#endif
-    /* use DMA if drive & controller supports it */
-    ata_dmainit(adp->controller, adp->unit,
-    		ata_pmode(AD_PARAM), ata_wmode(AD_PARAM), ata_umode(AD_PARAM));
+    /* enable write cacheing if allowed and not default on device */
+    if (ata_wc || ata_tags) {
+	if (ata_command(adp->controller, adp->unit, ATA_C_SETFEATURES,
+			0, 0, 0, 0, ATA_C_F_ENAB_WCACHE, ATA_WAIT_INTR))
+	ata_printf(scp, device, "enabling write cache failed\n");
+    }
+    else {
+	if (ata_command(adp->controller, adp->unit, ATA_C_SETFEATURES,
+			0, 0, 0, 0, ATA_C_F_DIS_WCACHE, ATA_WAIT_INTR))
+	ata_printf(scp, device, "disabling write cache failed\n");
+    }
 
-    /* use tagged queueing if supported */
-    if (ad_tagsupported(adp)) {
+    /* use DMA if allowed and if drive/controller supports it */
+    if (ata_dma)
+	ata_dmainit(adp->controller, adp->unit, ata_pmode(AD_PARAM), 
+		    ata_wmode(AD_PARAM), ata_umode(AD_PARAM));
+    else
+	ata_dmainit(adp->controller, adp->unit, ata_pmode(AD_PARAM), -1, -1);
+ 
+    /* use tagged queueing if allowed and supported */
+    if (ata_tags && ad_tagsupported(adp)) {
 	adp->num_tags = AD_PARAM->queuelen;
 	adp->flags |= AD_F_TAG_ENABLED;
 	adp->controller->flags |= ATA_QUEUED;