From a93726254b29a12c735a7877e51bdaeb5f889724 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Fri, 11 Apr 2008 11:11:28 +0000
Subject: [PATCH] Changed linux/kref.h compatibility header to make the API
 appear to be like it is in the 2.6.12 kernel.

---
 comedi/drivers/dt9812.c |  6 ++--
 include/linux/kref.h    | 69 ++++++++++++++---------------------------
 2 files changed, 27 insertions(+), 48 deletions(-)

diff --git a/comedi/drivers/dt9812.c b/comedi/drivers/dt9812.c
index 24177068..c3e8a60b 100644
--- a/comedi/drivers/dt9812.c
+++ b/comedi/drivers/dt9812.c
@@ -486,7 +486,7 @@ static int dt9812_probe(struct usb_interface *interface,
 		err("Out of memory");
 		goto error;
 	}
-	KREF_INIT(&dev->kref, dt9812_delete);
+	kref_init(&dev->kref);
 
 	dev->udev = usb_get_dev(interface_to_usbdev(interface));
 	dev->interface = interface;
@@ -644,7 +644,7 @@ static int dt9812_probe(struct usb_interface *interface,
 
       error:
 	if (dev) {
-		KREF_PUT(&dev->kref, dt9812_delete);
+		kref_put(&dev->kref, dt9812_delete);
 	}
 	return retval;
 }
@@ -666,7 +666,7 @@ static void dt9812_disconnect(struct usb_interface *interface)
 	up(&dt9812_mutex);
 
 	/* queue final destruction */
-	KREF_PUT(&dev->kref, dt9812_delete);
+	kref_put(&dev->kref, dt9812_delete);
 
 	info("USB Dt9812 #%d now disconnected", minor);
 }
diff --git a/include/linux/kref.h b/include/linux/kref.h
index 87ac9054..e939abd9 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -55,70 +55,49 @@ static inline int kref_put(struct kref *kref,
 	return 0;
 }
 
-static inline void KREF_INIT(struct kref *kref,
-	void (*release) (struct kref * kref))
-{
-	kref_init(kref);
-}
-
-static inline int KREF_PUT(struct kref *kref,
-	void (*release) (struct kref * kref))
-{
-	return kref_put(kref, release);
-}
-
 #else
 
 #include_next <linux/kref.h>
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,12)
+#include <asm/bug.h>
+#endif
+
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,9)
 
-static inline void KREF_INIT(struct kref *kref,
-	void (*release) (struct kref * kref))
+/* Dummy release function should never be called. */
+static void comedi_dummy_kref_release(struct kref *kref)
 {
-	kref_init(kref, release);
+	BUG();
 }
 
-static inline int KREF_PUT(struct kref *kref,
-	void (*release) (struct kref * kref))
+/* Redefine kref_init to remove 'release' parameter. */
+static inline void comedi_internal_kref_init(struct kref *kref)
 {
-	int retval;
-	if (atomic_read(&kref->refcount) == 1) {
-		retval = 1;
-	} else {
-		retval = 0;
-	}
-	kref_put(kref);
-	return retval;
+	kref_init(kref, comedi_dummy_kref_release);
 }
+#undef kref_init
+#define kref_init(kref) comedi_internal_kref_init(kref)
 
-#else
+#endif /* LINUX_VERSION_CODE < KERNEL_VERSION(2,6,9) */
 
-static inline void KREF_INIT(struct kref *kref,
-	void (*release) (struct kref * kref))
-{
-	kref_init(kref);
-}
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,12)
 
-static inline int KREF_PUT(struct kref *kref,
+/* Redefine kref_put to add 'release' parameter and return a result. */
+static inline int comedi_internal_kref_put(struct kref *kref,
 	void (*release) (struct kref * kref))
 {
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,12)
-	int retval;
-	if (atomic_read(&kref->refcount) == 1) {
-		retval = 1;
-	} else {
-		retval = 0;
+	if (atomic_dec_and_test(&kref->refcount)) {
+		release(kref);
+		return 1;
 	}
-	kref_put(kref, release);
-	return retval;
-#else
-	return kref_put(kref, release);
-#endif // LINUX_VERSION_CODE < KERNEL_VERSION(2,6,12)
+	return 0;
 }
+#undef kref_put
+#define kref_put(kref, release) comedi_internal_kref_put(kref, release)
 
-#endif // LINUX_VERSION_CODE < KERNEL_VERSION(2,6,9)
+#endif /* LINUX_VERSION_CODE < KERNEL_VERSION(2,6,12) */
 
-#endif // LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
+#endif /* LINUX_VERSION_CODE < KERNEL_VERSION(2,6,5) */
 
 #endif /* _KREF_COMPAT_H_ */
-- 
2.26.2