libata: beef up iterators

There currently are the following looping constructs.

* __ata_port_for_each_link() for all available links
* ata_port_for_each_link() for edge links
* ata_link_for_each_dev() for all devices
* ata_link_for_each_dev_reverse() for all devices in reverse order

Now there's a need for looping construct which is similar to
__ata_port_for_each_link() but iterates over PMP links before the host
link.  Instead of adding another one with long name, do the following
cleanup.

* Implement and export ata_link_next() and ata_dev_next() which take
  @mode parameter and can be used to build custom loop.
* Implement ata_for_each_link() and ata_for_each_dev() which take
  looping mode explicitly.

The following iteration modes are implemented.

* ATA_LITER_EDGE		: loop over edge links
* ATA_LITER_HOST_FIRST		: loop over all links, host link first
* ATA_LITER_PMP_FIRST		: loop over all links, PMP links first

* ATA_DITER_ENABLED		: loop over enabled devices
* ATA_DITER_ENABLED_REVERSE	: loop over enabled devices in reverse order
* ATA_DITER_ALL			: loop over all devices
* ATA_DITER_ALL_REVERSE		: loop over all devices in reverse order

This change removes exlicit device enabledness checks from many loops
and makes it clear which ones are iterated over in which direction.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 56 insertions, 20 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index ed3f26eb5df..3b2a0c6444e 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -1285,26 +1285,62 @@ static inline int ata_link_active(struct ata_link *link)
 	return ata_tag_valid(link->active_tag) || link->sactive;
 }
 
-extern struct ata_link *__ata_port_next_link(struct ata_port *ap,
-					     struct ata_link *link,
-					     bool dev_only);
-
-#define __ata_port_for_each_link(link, ap) \
-	for ((link) = __ata_port_next_link((ap), NULL, false); (link); \
-	     (link) = __ata_port_next_link((ap), (link), false))
-
-#define ata_port_for_each_link(link, ap) \
-	for ((link) = __ata_port_next_link((ap), NULL, true); (link); \
-	     (link) = __ata_port_next_link((ap), (link), true))
-
-#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)--)
+/*
+ * Iterators
+ *
+ * ATA_LITER_* constants are used to select link iteration mode and
+ * ATA_DITER_* device iteration mode.
+ *
+ * For a custom iteration directly using ata_{link|dev}_next(), if
+ * @link or @dev, respectively, is NULL, the first element is
+ * returned.  @dev and @link can be any valid device or link and the
+ * next element according to the iteration mode will be returned.
+ * After the last element, NULL is returned.
+ */
+enum ata_link_iter_mode {
+	ATA_LITER_EDGE,		/* if present, PMP links only; otherwise,
+				 * host link.  no slave link */
+	ATA_LITER_HOST_FIRST,	/* host link followed by PMP or slave links */
+	ATA_LITER_PMP_FIRST,	/* PMP links followed by host link,
+				 * slave link still comes after host link */
+};
+
+enum ata_dev_iter_mode {
+	ATA_DITER_ENABLED,
+	ATA_DITER_ENABLED_REVERSE,
+	ATA_DITER_ALL,
+	ATA_DITER_ALL_REVERSE,
+};
+
+extern struct ata_link *ata_link_next(struct ata_link *link,
+				      struct ata_port *ap,
+				      enum ata_link_iter_mode mode);
+
+extern struct ata_device *ata_dev_next(struct ata_device *dev,
+				       struct ata_link *link,
+				       enum ata_dev_iter_mode mode);
+
+/*
+ * Shortcut notation for iterations
+ *
+ * ata_for_each_link() iterates over each link of @ap according to
+ * @mode.  @link points to the current link in the loop.  @link is
+ * NULL after loop termination.  ata_for_each_dev() works the same way
+ * except that it iterates over each device of @link.
+ *
+ * Note that the mode prefixes ATA_{L|D}ITER_ shouldn't need to be
+ * specified when using the following shorthand notations.  Only the
+ * mode itself (EDGE, HOST_FIRST, ENABLED, etc...) should be
+ * specified.  This not only increases brevity but also makes it
+ * impossible to use ATA_LITER_* for device iteration or vice-versa.
+ */
+#define ata_for_each_link(link, ap, mode) \
+	for ((link) = ata_link_next(NULL, (ap), ATA_LITER_##mode); (link); \
+	     (link) = ata_link_next((link), (ap), ATA_LITER_##mode))
+
+#define ata_for_each_dev(dev, link, mode) \
+	for ((dev) = ata_dev_next(NULL, (link), ATA_DITER_##mode); (dev); \
+	     (dev) = ata_dev_next((dev), (link), ATA_DITER_##mode))
 
 /**
  *	ata_ncq_enabled - Test whether NCQ is enabled