libata-link: implement and use link/device iterators

Multiple links and different number of devices per link should be
considered to iterate over links and devices.  This patch implements
and uses link and device iterators - ata_port_for_each_link() and
ata_link_for_each_dev() - and ata_link_max_devices().

This change makes a lot of functions iterate over only possible
devices instead of from dev 0 to dev ATA_MAX_DEVICES.  All such
changes have been examined and nothing should be broken.

While at it, add a separating comment before device helpers to
distinguish them better from link helpers and others.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

13 files changed, 134 insertions, 148 deletions

diff --git a/drivers/ata/ata_generic.c b/drivers/ata/ata_generic.c
index b5e390ff5bd8..44328a16075c 100644
--- a/drivers/ata/ata_generic.c
+++ b/drivers/ata/ata_generic.c
@@ -46,21 +46,20 @@
 static int generic_set_mode(struct ata_port *ap, struct ata_device **unused)
 {
 	int dma_enabled = 0;
-	int i;
+	struct ata_device *dev;
 
 	/* Bits 5 and 6 indicate if DMA is active on master/slave */
 	if (ap->ioaddr.bmdma_addr)
 		dma_enabled = ioread8(ap->ioaddr.bmdma_addr + ATA_DMA_STATUS);
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (ata_dev_enabled(dev)) {
 			/* We don't really care */
 			dev->pio_mode = XFER_PIO_0;
 			dev->dma_mode = XFER_MW_DMA_0;
 			/* We do need the right mode information for DMA or PIO
 			   and this comes from the current configuration flags */
-			if (dma_enabled & (1 << (5 + i))) {
+			if (dma_enabled & (1 << (5 + dev->devno))) {
 				ata_id_to_dma_mode(dev, XFER_MW_DMA_0);
 				dev->flags &= ~ATA_DFLAG_PIO;
 			} else {
diff --git a/drivers/ata/libata-acpi.c b/drivers/ata/libata-acpi.c
index 0023ac4ff496..43af2e06d446 100644
--- a/drivers/ata/libata-acpi.c
+++ b/drivers/ata/libata-acpi.c
@@ -509,7 +509,7 @@ int ata_acpi_on_suspend(struct ata_port *ap)
  */
 void ata_acpi_on_resume(struct ata_port *ap)
 {
-	int i;
+	struct ata_device *dev;
 
 	if (ap->acpi_handle && (ap->pflags & ATA_PFLAG_GTM_VALID)) {
 		BUG_ON(ap->flags & ATA_FLAG_ACPI_SATA);
@@ -519,8 +519,8 @@ void ata_acpi_on_resume(struct ata_port *ap)
 	}
 
 	/* schedule _GTF */
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		ap->link.device[i].flags |= ATA_DFLAG_ACPI_PENDING;
+	ata_link_for_each_dev(dev, &ap->link)
+		dev->flags |= ATA_DFLAG_ACPI_PENDING;
 }
 
 /**
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index dd2de485124a..f30c4771b3af 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -2105,21 +2105,19 @@ int ata_bus_probe(struct ata_port *ap)
 {
 	unsigned int classes[ATA_MAX_DEVICES];
 	int tries[ATA_MAX_DEVICES];
-	int i, rc;
+	int rc;
 	struct ata_device *dev;
 
 	ata_port_probe(ap);
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		tries[i] = ATA_PROBE_MAX_TRIES;
+	ata_link_for_each_dev(dev, &ap->link)
+		tries[dev->devno] = ATA_PROBE_MAX_TRIES;
 
  retry:
 	/* reset and determine device classes */
 	ap->ops->phy_reset(ap);
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		dev = &ap->link.device[i];
-
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (!(ap->flags & ATA_FLAG_DISABLED) &&
 		    dev->class != ATA_DEV_UNKNOWN)
 			classes[dev->devno] = dev->class;
@@ -2134,18 +2132,16 @@ int ata_bus_probe(struct ata_port *ap)
 	/* after the reset the device state is PIO 0 and the controller
 	   state is undefined. Record the mode */
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		ap->link.device[i].pio_mode = XFER_PIO_0;
+	ata_link_for_each_dev(dev, &ap->link)
+		dev->pio_mode = XFER_PIO_0;
 
 	/* read IDENTIFY page and configure devices. We have to do the identify
 	   specific sequence bass-ackwards so that PDIAG- is released by
 	   the slave device */
 
-	for (i = ATA_MAX_DEVICES - 1; i >=  0; i--) {
-		dev = &ap->link.device[i];
-
-		if (tries[i])
-			dev->class = classes[i];
+	ata_link_for_each_dev(dev, &ap->link) {
+		if (tries[dev->devno])
+			dev->class = classes[dev->devno];
 
 		if (!ata_dev_enabled(dev))
 			continue;
@@ -2163,8 +2159,7 @@ int ata_bus_probe(struct ata_port *ap)
 	/* After the identify sequence we can now set up the devices. We do
 	   this in the normal order so that the user doesn't get confused */
 
-	for(i = 0; i < ATA_MAX_DEVICES; i++) {
-		dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (!ata_dev_enabled(dev))
 			continue;
 
@@ -2180,8 +2175,8 @@ int ata_bus_probe(struct ata_port *ap)
 	if (rc)
 		goto fail;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		if (ata_dev_enabled(&ap->link.device[i]))
+	ata_link_for_each_dev(dev, &ap->link)
+		if (ata_dev_enabled(dev))
 			return 0;
 
 	/* no device present, disable port */
@@ -2803,16 +2798,14 @@ static int ata_dev_set_mode(struct ata_device *dev)
 
 int ata_do_set_mode(struct ata_port *ap, struct ata_device **r_failed_dev)
 {
+	struct ata_link *link = &ap->link;
 	struct ata_device *dev;
-	int i, rc = 0, used_dma = 0, found = 0;
-
+	int rc = 0, used_dma = 0, found = 0;
 
 	/* step 1: calculate xfer_mask */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
+	ata_link_for_each_dev(dev, link) {
 		unsigned int pio_mask, dma_mask;
 
-		dev = &ap->link.device[i];
-
 		if (!ata_dev_enabled(dev))
 			continue;
 
@@ -2831,8 +2824,7 @@ int ata_do_set_mode(struct ata_port *ap, struct ata_device **r_failed_dev)
 		goto out;
 
 	/* step 2: always set host PIO timings */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, link) {
 		if (!ata_dev_enabled(dev))
 			continue;
 
@@ -2849,9 +2841,7 @@ int ata_do_set_mode(struct ata_port *ap, struct ata_device **r_failed_dev)
 	}
 
 	/* step 3: set host DMA timings */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		dev = &ap->link.device[i];
-
+	ata_link_for_each_dev(dev, link) {
 		if (!ata_dev_enabled(dev) || !dev->dma_mode)
 			continue;
 
@@ -2862,9 +2852,7 @@ int ata_do_set_mode(struct ata_port *ap, struct ata_device **r_failed_dev)
 	}
 
 	/* step 4: update devices' xfer mode */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		dev = &ap->link.device[i];
-
+	ata_link_for_each_dev(dev, link) {
 		/* don't update suspended devices' xfer mode */
 		if (!ata_dev_enabled(dev))
 			continue;
@@ -6113,6 +6101,7 @@ struct ata_port *ata_port_alloc(struct ata_host *host)
 
 	ap->link.ap = ap;
 
+	/* can't use iterator, ap isn't initialized yet */
 	for (i = 0; i < ATA_MAX_DEVICES; i++) {
 		struct ata_device *dev = &ap->link.device[i];
 		dev->link = &ap->link;
@@ -6453,7 +6442,8 @@ int ata_host_register(struct ata_host *host, struct scsi_host_template *sht)
 			/* kick EH for boot probing */
 			spin_lock_irqsave(ap->lock, flags);
 
-			ehi->probe_mask = (1 << ATA_MAX_DEVICES) - 1;
+			ehi->probe_mask =
+				(1 << ata_link_max_devices(&ap->link)) - 1;
 			ehi->action |= ATA_EH_SOFTRESET;
 			ehi->flags |= ATA_EHI_NO_AUTOPSY | ATA_EHI_QUIET;
 
@@ -6551,7 +6541,7 @@ int ata_host_activate(struct ata_host *host, int irq,
 void ata_port_detach(struct ata_port *ap)
 {
 	unsigned long flags;
-	int i;
+	struct ata_device *dev;
 
 	if (!ap->ops->error_handler)
 		goto skip_eh;
@@ -6568,8 +6558,8 @@ void ata_port_detach(struct ata_port *ap)
 	 */
 	spin_lock_irqsave(ap->lock, flags);
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		ata_dev_disable(&ap->link.device[i]);
+	ata_link_for_each_dev(dev, &ap->link)
+		ata_dev_disable(dev);
 
 	spin_unlock_irqrestore(ap->lock, flags);
 
diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index e2681f56ed44..8c37ec0bbf6c 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -200,23 +200,24 @@ static unsigned int ata_eh_dev_action(struct ata_device *dev)
 	return ehc->i.action | ehc->i.dev_action[dev->devno];
 }
 
-static void ata_eh_clear_action(struct ata_device *dev,
+static void ata_eh_clear_action(struct ata_link *link, struct ata_device *dev,
 				struct ata_eh_info *ehi, unsigned int action)
 {
-	int i;
+	struct ata_device *tdev;
 
 	if (!dev) {
 		ehi->action &= ~action;
-		for (i = 0; i < ATA_MAX_DEVICES; i++)
-			ehi->dev_action[i] &= ~action;
+		ata_link_for_each_dev(tdev, link)
+			ehi->dev_action[tdev->devno] &= ~action;
 	} else {
 		/* doesn't make sense for port-wide EH actions */
 		WARN_ON(!(action & ATA_EH_PERDEV_MASK));
 
 		/* break ehi->action into ehi->dev_action */
 		if (ehi->action & action) {
-			for (i = 0; i < ATA_MAX_DEVICES; i++)
-				ehi->dev_action[i] |= ehi->action & action;
+			ata_link_for_each_dev(tdev, link)
+				ehi->dev_action[tdev->devno] |=
+					ehi->action & action;
 			ehi->action &= ~action;
 		}
 
@@ -922,7 +923,8 @@ void ata_eh_qc_retry(struct ata_queued_cmd *qc)
  */
 static void ata_eh_detach_dev(struct ata_device *dev)
 {
-	struct ata_port *ap = dev->link->ap;
+	struct ata_link *link = dev->link;
+	struct ata_port *ap = link->ap;
 	unsigned long flags;
 
 	ata_dev_disable(dev);
@@ -937,8 +939,8 @@ static void ata_eh_detach_dev(struct ata_device *dev)
 	}
 
 	/* clear per-dev EH actions */
-	ata_eh_clear_action(dev, &dev->link->eh_info, ATA_EH_PERDEV_MASK);
-	ata_eh_clear_action(dev, &dev->link->eh_context.i, ATA_EH_PERDEV_MASK);
+	ata_eh_clear_action(link, dev, &link->eh_info, ATA_EH_PERDEV_MASK);
+	ata_eh_clear_action(link, dev, &link->eh_context.i, ATA_EH_PERDEV_MASK);
 
 	spin_unlock_irqrestore(ap->lock, flags);
 }
@@ -978,7 +980,7 @@ static void ata_eh_about_to_do(struct ata_port *ap, struct ata_device *dev,
 		ehi->flags &= ~ATA_EHI_RESET_MODIFIER_MASK;
 	}
 
-	ata_eh_clear_action(dev, ehi, action);
+	ata_eh_clear_action(&ap->link, dev, ehi, action);
 
 	if (!(ehc->i.flags & ATA_EHI_QUIET))
 		ap->pflags |= ATA_PFLAG_RECOVERED;
@@ -1009,7 +1011,7 @@ static void ata_eh_done(struct ata_port *ap, struct ata_device *dev,
 		ehc->i.flags &= ~ATA_EHI_RESET_MODIFIER_MASK;
 	}
 
-	ata_eh_clear_action(dev, &ehc->i, action);
+	ata_eh_clear_action(&ap->link, dev, &ehc->i, action);
 }
 
 /**
@@ -1736,10 +1738,11 @@ static void ata_eh_report(struct ata_port *ap)
 static int ata_do_reset(struct ata_port *ap, ata_reset_fn_t reset,
 			unsigned int *classes, unsigned long deadline)
 {
-	int i, rc;
+	struct ata_device *dev;
+	int rc;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		classes[i] = ATA_DEV_UNKNOWN;
+	ata_link_for_each_dev(dev, &ap->link)
+		classes[dev->devno] = ATA_DEV_UNKNOWN;
 
 	rc = reset(ap, classes, deadline);
 	if (rc)
@@ -1749,14 +1752,16 @@ static int ata_do_reset(struct ata_port *ap, ata_reset_fn_t reset,
 	 * is complete and convert all ATA_DEV_UNKNOWN to
 	 * ATA_DEV_NONE.
 	 */
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		if (classes[i] != ATA_DEV_UNKNOWN)
+	ata_link_for_each_dev(dev, &ap->link)
+		if (classes[dev->devno] != ATA_DEV_UNKNOWN)
 			break;
 
-	if (i < ATA_MAX_DEVICES)
-		for (i = 0; i < ATA_MAX_DEVICES; i++)
-			if (classes[i] == ATA_DEV_UNKNOWN)
-				classes[i] = ATA_DEV_NONE;
+	if (dev) {
+		ata_link_for_each_dev(dev, &ap->link) {
+			if (classes[dev->devno] == ATA_DEV_UNKNOWN)
+				classes[dev->devno] = ATA_DEV_NONE;
+		}
+	}
 
 	return 0;
 }
@@ -1781,10 +1786,11 @@ static int ata_eh_reset(struct ata_port *ap, int classify,
 	unsigned int *classes = ehc->classes;
 	int verbose = !(ehc->i.flags & ATA_EHI_QUIET);
 	int try = 0;
+	struct ata_device *dev;
 	unsigned long deadline;
 	unsigned int action;
 	ata_reset_fn_t reset;
-	int i, rc;
+	int rc;
 
 	/* about to reset */
 	ata_eh_about_to_do(ap, NULL, ehc->i.action & ATA_EH_RESET_MASK);
@@ -1808,8 +1814,8 @@ static int ata_eh_reset(struct ata_port *ap, int classify,
 						"port disabled. ignoring.\n");
 				ehc->i.action &= ~ATA_EH_RESET_MASK;
 
-				for (i = 0; i < ATA_MAX_DEVICES; i++)
-					classes[i] = ATA_DEV_NONE;
+				ata_link_for_each_dev(dev, &ap->link)
+					classes[dev->devno] = ATA_DEV_NONE;
 
 				rc = 0;
 			} else
@@ -1826,8 +1832,8 @@ static int ata_eh_reset(struct ata_port *ap, int classify,
 		reset = softreset;
 	else {
 		/* prereset told us not to reset, bang classes and return */
-		for (i = 0; i < ATA_MAX_DEVICES; i++)
-			classes[i] = ATA_DEV_NONE;
+		ata_link_for_each_dev(dev, &ap->link)
+			classes[dev->devno] = ATA_DEV_NONE;
 		rc = 0;
 		goto out;
 	}
@@ -1908,8 +1914,8 @@ static int ata_eh_reset(struct ata_port *ap, int classify,
 		/* After the reset, the device state is PIO 0 and the
 		 * controller state is undefined.  Record the mode.
 		 */
-		for (i = 0; i < ATA_MAX_DEVICES; i++)
-			ap->link.device[i].pio_mode = XFER_PIO_0;
+		ata_link_for_each_dev(dev, &ap->link)
+			dev->pio_mode = XFER_PIO_0;
 
 		/* record current link speed */
 		if (sata_scr_read(ap, SCR_STATUS, &sstatus) == 0)
@@ -1935,7 +1941,7 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
 	struct ata_device *dev;
 	unsigned int new_mask = 0;
 	unsigned long flags;
-	int i, rc = 0;
+	int rc = 0;
 
 	DPRINTK("ENTER\n");
 
@@ -1943,11 +1949,9 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
 	 * be done backwards such that PDIAG- is released by the slave
 	 * device before the master device is identified.
 	 */
-	for (i = ATA_MAX_DEVICES - 1; i >= 0; i--) {
-		unsigned int action, readid_flags = 0;
-
-		dev = &ap->link.device[i];
-		action = ata_eh_dev_action(dev);
+	ata_link_for_each_dev_reverse(dev, &ap->link) {
+		unsigned int action = ata_eh_dev_action(dev);
+		unsigned int readid_flags = 0;
 
 		if (ehc->i.flags & ATA_EHI_DID_RESET)
 			readid_flags |= ATA_READID_POSTRESET;
@@ -1981,7 +1985,7 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
 					     dev->id);
 			switch (rc) {
 			case 0:
-				new_mask |= 1 << i;
+				new_mask |= 1 << dev->devno;
 				break;
 			case -ENOENT:
 				/* IDENTIFY was issued to non-existent
@@ -2005,10 +2009,8 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
 	/* Configure new devices forward such that user doesn't see
 	 * device detection messages backwards.
 	 */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		dev = &ap->link.device[i];
-
-		if (!(new_mask & (1 << i)))
+	ata_link_for_each_dev(dev, &ap->link) {
+		if (!(new_mask & (1 << dev->devno)))
 			continue;
 
 		ehc->i.flags |= ATA_EHI_PRINTINFO;
@@ -2035,20 +2037,22 @@ static int ata_eh_revalidate_and_attach(struct ata_port *ap,
 
 static int ata_port_nr_enabled(struct ata_port *ap)
 {
-	int i, cnt = 0;
+	struct ata_device *dev;
+	int cnt = 0;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		if (ata_dev_enabled(&ap->link.device[i]))
+	ata_link_for_each_dev(dev, &ap->link)
+		if (ata_dev_enabled(dev))
 			cnt++;
 	return cnt;
 }
 
 static int ata_port_nr_vacant(struct ata_port *ap)
 {
-	int i, cnt = 0;
+	struct ata_device *dev;
+	int cnt = 0;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		if (ap->link.device[i].class == ATA_DEV_UNKNOWN)
+	ata_link_for_each_dev(dev, &ap->link)
+		if (dev->class == ATA_DEV_UNKNOWN)
 			cnt++;
 	return cnt;
 }
@@ -2056,7 +2060,7 @@ static int ata_port_nr_vacant(struct ata_port *ap)
 static int ata_eh_skip_recovery(struct ata_port *ap)
 {
 	struct ata_eh_context *ehc = &ap->link.eh_context;
-	int i;
+	struct ata_device *dev;
 
 	/* thaw frozen port, resume link and recover failed devices */
 	if ((ap->pflags & ATA_PFLAG_FROZEN) ||
@@ -2064,9 +2068,7 @@ static int ata_eh_skip_recovery(struct ata_port *ap)
 		return 0;
 
 	/* skip if class codes for all vacant slots are ATA_DEV_NONE */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
-
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (dev->class == ATA_DEV_UNKNOWN &&
 		    ehc->classes[dev->devno] != ATA_DEV_NONE)
 			return 0;
@@ -2153,19 +2155,18 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 {
 	struct ata_eh_context *ehc = &ap->link.eh_context;
 	struct ata_device *dev;
-	int i, rc;
+	int rc;
 
 	DPRINTK("ENTER\n");
 
 	/* prep for recovery */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		dev = &ap->link.device[i];
-
+	ata_link_for_each_dev(dev, &ap->link) {
 		ehc->tries[dev->devno] = ATA_EH_DEV_TRIES;
 
 		/* collect port action mask recorded in dev actions */
-		ehc->i.action |= ehc->i.dev_action[i] & ~ATA_EH_PERDEV_MASK;
-		ehc->i.dev_action[i] &= ATA_EH_PERDEV_MASK;
+		ehc->i.action |=
+			ehc->i.dev_action[dev->devno] & ~ATA_EH_PERDEV_MASK;
+		ehc->i.dev_action[dev->devno] &= ATA_EH_PERDEV_MASK;
 
 		/* process hotplug request */
 		if (dev->flags & ATA_DFLAG_DETACH)
@@ -2192,8 +2193,8 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 	if (ata_eh_skip_recovery(ap))
 		ehc->i.action = 0;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++)
-		ehc->classes[i] = ATA_DEV_UNKNOWN;
+	ata_link_for_each_dev(dev, &ap->link)
+		ehc->classes[dev->devno] = ATA_DEV_UNKNOWN;
 
 	/* reset */
 	if (ehc->i.action & ATA_EH_RESET_MASK) {
@@ -2241,8 +2242,8 @@ static int ata_eh_recover(struct ata_port *ap, ata_prereset_fn_t prereset,
 
  out:
 	if (rc) {
-		for (i = 0; i < ATA_MAX_DEVICES; i++)
-			ata_dev_disable(&ap->link.device[i]);
+		ata_link_for_each_dev(dev, &ap->link);
+			ata_dev_disable(dev);
 	}
 
 	DPRINTK("EXIT, rc=%d\n", rc);
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index ec0e2638200e..3d6d5f737994 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -2425,7 +2425,7 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc)
 
 static struct ata_device * ata_find_dev(struct ata_port *ap, int id)
 {
-	if (likely(id < ATA_MAX_DEVICES))
+	if (likely(id < ata_link_max_devices(&ap->link)))
 		return &ap->link.device[id];
 	return NULL;
 }
@@ -2952,21 +2952,18 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
 	int tries = 5;
 	struct ata_device *last_failed_dev = NULL;
 	struct ata_device *dev;
-	unsigned int i;
 
 	if (ap->flags & ATA_FLAG_DISABLED)
 		return;
 
  repeat:
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
+	ata_link_for_each_dev(dev, &ap->link) {
 		struct scsi_device *sdev;
 
-		dev = &ap->link.device[i];
-
 		if (!ata_dev_enabled(dev) || dev->sdev)
 			continue;
 
-		sdev = __scsi_add_device(ap->scsi_host, 0, i, 0, NULL);
+		sdev = __scsi_add_device(ap->scsi_host, 0, dev->devno, 0, NULL);
 		if (!IS_ERR(sdev)) {
 			dev->sdev = sdev;
 			scsi_device_put(sdev);
@@ -2977,12 +2974,11 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
 	 * failure occurred, scan would have failed silently.  Check
 	 * whether all devices are attached.
 	 */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (ata_dev_enabled(dev) && !dev->sdev)
 			break;
 	}
-	if (i == ATA_MAX_DEVICES)
+	if (!dev)
 		return;
 
 	/* we're missing some SCSI devices */
@@ -3112,7 +3108,7 @@ void ata_scsi_hotplug(struct work_struct *work)
 {
 	struct ata_port *ap =
 		container_of(work, struct ata_port, hotplug_task.work);
-	int i;
+	struct ata_device *dev;
 
 	if (ap->pflags & ATA_PFLAG_UNLOADING) {
 		DPRINTK("ENTER/EXIT - unloading\n");
@@ -3122,8 +3118,7 @@ void ata_scsi_hotplug(struct work_struct *work)
 	DPRINTK("ENTER\n");
 
 	/* unplug detached devices */
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		unsigned long flags;
 
 		if (!(dev->flags & ATA_DFLAG_DETACHED))
@@ -3176,7 +3171,7 @@ static int ata_scsi_user_scan(struct Scsi_Host *shost, unsigned int channel,
 	spin_lock_irqsave(ap->lock, flags);
 
 	if (id == SCAN_WILD_CARD) {
-		ehi->probe_mask |= (1 << ATA_MAX_DEVICES) - 1;
+		ehi->probe_mask |= (1 << ata_link_max_devices(&ap->link)) - 1;
 		ehi->action |= ATA_EH_SOFTRESET;
 	} else {
 		struct ata_device *dev = ata_find_dev(ap, id);
@@ -3215,13 +3210,12 @@ void ata_scsi_dev_rescan(struct work_struct *work)
 {
 	struct ata_port *ap =
 		container_of(work, struct ata_port, scsi_rescan_task);
+	struct ata_device *dev;
 	unsigned long flags;
-	unsigned int i;
 
 	spin_lock_irqsave(ap->lock, flags);
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		struct scsi_device *sdev = dev->sdev;
 
 		if (!ata_dev_enabled(dev) || !sdev)
diff --git a/drivers/ata/pata_it821x.c b/drivers/ata/pata_it821x.c
index ece1a28f0a4a..088eb1d23761 100644
--- a/drivers/ata/pata_it821x.c
+++ b/drivers/ata/pata_it821x.c
@@ -461,10 +461,9 @@ static unsigned int it821x_passthru_qc_issue_prot(struct ata_queued_cmd *qc)
 
 static int it821x_smart_set_mode(struct ata_port *ap, struct ata_device **unused)
 {
-	int i;
+	struct ata_device *dev;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (ata_dev_enabled(dev)) {
 			/* We don't really care */
 			dev->pio_mode = XFER_PIO_0;
diff --git a/drivers/ata/pata_ixp4xx_cf.c b/drivers/ata/pata_ixp4xx_cf.c
index 3e2b8ce5fa37..7db315a9baad 100644
--- a/drivers/ata/pata_ixp4xx_cf.c
+++ b/drivers/ata/pata_ixp4xx_cf.c
@@ -28,10 +28,9 @@
 
 static int ixp4xx_set_mode(struct ata_port *ap, struct ata_device **error)
 {
-	int i;
+	struct ata_device *dev;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (ata_dev_enabled(dev)) {
 			ata_dev_printk(dev, KERN_INFO, "configured for PIO0\n");
 			dev->pio_mode = XFER_PIO_0;
diff --git a/drivers/ata/pata_legacy.c b/drivers/ata/pata_legacy.c
index 4bcc0ae8d108..9d92843b033d 100644
--- a/drivers/ata/pata_legacy.c
+++ b/drivers/ata/pata_legacy.c
@@ -109,10 +109,9 @@ static int iordy_mask = 0xFFFFFFFF;	/* Use iordy if available */
 
 static int legacy_set_mode(struct ata_port *ap, struct ata_device **unused)
 {
-	int i;
+	struct ata_device *dev;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (ata_dev_enabled(dev)) {
 			ata_dev_printk(dev, KERN_INFO, "configured for PIO\n");
 			dev->pio_mode = XFER_PIO_0;
diff --git a/drivers/ata/pata_pdc2027x.c b/drivers/ata/pata_pdc2027x.c
index fa780509a1dc..83c90cabc7ff 100644
--- a/drivers/ata/pata_pdc2027x.c
+++ b/drivers/ata/pata_pdc2027x.c
@@ -479,15 +479,14 @@ static void pdc2027x_set_dmamode(struct ata_port *ap, struct ata_device *adev)
  */
 static int pdc2027x_set_mode(struct ata_port *ap, struct ata_device **r_failed)
 {
-	int i;
-
-	i = ata_do_set_mode(ap, r_failed);
-	if (i < 0)
-		return i;
+	struct ata_device *dev;
+	int rc;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	rc = ata_do_set_mode(ap, r_failed);
+	if (rc < 0)
+		return rc;
 
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (ata_dev_enabled(dev)) {
 
 			pdc2027x_set_piomode(ap, dev);
diff --git a/drivers/ata/pata_platform.c b/drivers/ata/pata_platform.c
index e89656bffa84..ee1605bfc29f 100644
--- a/drivers/ata/pata_platform.c
+++ b/drivers/ata/pata_platform.c
@@ -32,11 +32,9 @@ static int pio_mask = 1;
  */
 static int pata_platform_set_mode(struct ata_port *ap, struct ata_device **unused)
 {
-	int i;
-
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	struct ata_device *dev;
 
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (ata_dev_enabled(dev)) {
 			/* We don't really care */
 			dev->pio_mode = dev->xfer_mode = XFER_PIO_0;
diff --git a/drivers/ata/pata_rz1000.c b/drivers/ata/pata_rz1000.c
index 57363c0ce068..300b3d5de81e 100644
--- a/drivers/ata/pata_rz1000.c
+++ b/drivers/ata/pata_rz1000.c
@@ -36,10 +36,9 @@
 
 static int rz1000_set_mode(struct ata_port *ap, struct ata_device **unused)
 {
-	int i;
+	struct ata_device *dev;
 
-	for (i = 0; i < ATA_MAX_DEVICES; i++) {
-		struct ata_device *dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (ata_dev_enabled(dev)) {
 			/* We don't really care */
 			dev->pio_mode = XFER_PIO_0;
diff --git a/drivers/ata/sata_sil.c b/drivers/ata/sata_sil.c
index 2ddbe4cc71e4..4c9295a49a49 100644
--- a/drivers/ata/sata_sil.c
+++ b/drivers/ata/sata_sil.c
@@ -303,22 +303,20 @@ static int sil_set_mode (struct ata_port *ap, struct ata_device **r_failed)
 	struct ata_device *dev;
 	void __iomem *mmio_base = host->iomap[SIL_MMIO_BAR];
 	void __iomem *addr = mmio_base + sil_port[ap->port_no].xfer_mode;
-	u32 tmp, dev_mode[2];
-	unsigned int i;
+	u32 tmp, dev_mode[2] = { };
 	int rc;
 
 	rc = ata_do_set_mode(ap, r_failed);
 	if (rc)
 		return rc;
 
-	for (i = 0; i < 2; i++) {
-		dev = &ap->link.device[i];
+	ata_link_for_each_dev(dev, &ap->link) {
 		if (!ata_dev_enabled(dev))
-			dev_mode[i] = 0;	/* PIO0/1/2 */
+			dev_mode[dev->devno] = 0;	/* PIO0/1/2 */
 		else if (dev->flags & ATA_DFLAG_PIO)
-			dev_mode[i] = 1;	/* PIO3/4 */
+			dev_mode[dev->devno] = 1;	/* PIO3/4 */
 		else
-			dev_mode[i] = 3;	/* UDMA */
+			dev_mode[dev->devno] = 3;	/* UDMA */
 		/* value 2 indicates MDMA */
 	}
 
diff --git a/include/linux/libata.h b/include/linux/libata.h
index ca4493125fa0..62fa8cf677a1 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -1030,15 +1030,26 @@ static inline unsigned int ata_dev_absent(const struct ata_device *dev)
 }
 
 /*
- * port helpers
+ * link helpers
  */
-static inline int ata_port_max_devices(const struct ata_port *ap)
+static inline int ata_link_max_devices(const struct ata_link *link)
 {
-	if (ap->flags & ATA_FLAG_SLAVE_POSS)
+	if (link->ap->flags & ATA_FLAG_SLAVE_POSS)
 		return 2;
 	return 1;
 }
 
+#define ata_port_for_each_link(lk, ap) \
+	for ((lk) = &(ap)->link; (lk); (lk) = NULL)
+
+#define ata_link_for_each_dev(dev, link) \
+	for ((dev) = (link)->device; \
+	     (dev) < (link)->device + ata_link_max_devices(link) || ((dev) = NULL); \
+	     (dev)++)
+
+#define ata_link_for_each_dev_reverse(dev, link) \
+	for ((dev) = (link)->device + ata_link_max_devices(link) - 1; \
+	     (dev) >= (link)->device || ((dev) = NULL); (dev)--)
 
 static inline u8 ata_chk_status(struct ata_port *ap)
 {