Merge branch 'drm-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6

* 'drm-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6: (390 commits)
  drm/radeon/kms: disable underscan by default
  drm/radeon/kms: only enable hdmi features if the monitor supports audio
  drm: Restore the old_fb upon modeset failure
  drm/nouveau: fix hwmon device binding
  radeon: consolidate asic-specific function decls for pre-r600
  vga_switcheroo: comparing too few characters in strncmp()
  drm/radeon/kms: add NI pci ids
  drm/radeon/kms: don't enable pcie gen2 on NI yet
  drm/radeon/kms: add radeon_asic struct for NI asics
  drm/radeon/kms/ni: load default sclk/mclk/vddc at pm init
  drm/radeon/kms: add ucode loader for NI
  drm/radeon/kms: add support for DCE5 display LUTs
  drm/radeon/kms: add ni_reg.h
  drm/radeon/kms: add bo blit support for NI
  drm/radeon/kms: always use writeback/events for fences on NI
  drm/radeon/kms: adjust default clock/vddc tracking for pm on DCE5
  drm/radeon/kms: add backend map workaround for barts
  drm/radeon/kms: fill gpu init for NI asics
  drm/radeon/kms: add disabled vbios accessor for NI asics
  drm/radeon/kms: handle NI thermal controller
  ...

1 files changed, 30 insertions, 0 deletions

diff --git a/lib/kref.c b/lib/kref.c
index d3d227a08a4b..3efb882b11db 100644
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -62,6 +62,36 @@ int kref_put(struct kref *kref, void (*release)(struct kref *kref))
 	return 0;
 }
 
+
+/**
+ * kref_sub - subtract a number of refcounts for object.
+ * @kref: object.
+ * @count: Number of recounts to subtract.
+ * @release: pointer to the function that will clean up the object when the
+ *	     last reference to the object is released.
+ *	     This pointer is required, and it is not acceptable to pass kfree
+ *	     in as this function.
+ *
+ * Subtract @count from the refcount, and if 0, call release().
+ * Return 1 if the object was removed, otherwise return 0.  Beware, if this
+ * function returns 0, you still can not count on the kref from remaining in
+ * memory.  Only use the return value if you want to see if the kref is now
+ * gone, not present.
+ */
+int kref_sub(struct kref *kref, unsigned int count,
+	     void (*release)(struct kref *kref))
+{
+	WARN_ON(release == NULL);
+	WARN_ON(release == (void (*)(struct kref *))kfree);
+
+	if (atomic_sub_and_test((int) count, &kref->refcount)) {
+		release(kref);
+		return 1;
+	}
+	return 0;
+}
+
 EXPORT_SYMBOL(kref_init);
 EXPORT_SYMBOL(kref_get);
 EXPORT_SYMBOL(kref_put);
+EXPORT_SYMBOL(kref_sub);