kfifo: add DEFINE_KFIFO and friends, add very tiny functions

Add DECLARE_KFIFO - macro to declare a kfifo and the associated buffer inside a struct
 Add INIT_KFIFO - Initialize a kfifo declared by DECLARED_KFIFO
 Add DEFINE_KFIFO - macro to define and initialize a kfifo as a global or local object
 Add kfifo_size() - returns the size of the fifo in bytes
 Add kfifo_is_empty() - returns true if the fifo is empty
 Add kfifo_is_full() - returns true if the fifo is full
 Add kfifo_avail() - returns the number of bytes available in the FIFO
 Do some code cleanup

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 92 insertions, 2 deletions

diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index 5ed2565c89b6..dd53eed3e2af 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -51,6 +51,60 @@ struct kfifo {
         unsigned int out;       /* data is extracted from off. (out % size) */
 };
 
+/*
+ * Macros for declaration and initialization of the kfifo datatype
+ */
+
+/* helper macro */
+#define __kfifo_initializer(s, b) \
+        (struct kfifo) { \
+                .size   = s, \
+                .in     = 0, \
+                .out    = 0, \
+                .buffer = b \
+        }
+
+/**
+ * DECLARE_KFIFO - macro to declare a kfifo and the associated buffer
+ * @name: name of the declared kfifo datatype
+ * @size: size of the fifo buffer
+ *
+ * Note: the macro can be used inside struct or union declaration
+ * Note: the macro creates two objects:
+ *  A kfifo object with the given name and a buffer for the kfifo
+ *  object named name##kfifo_buffer
+ */
+#define DECLARE_KFIFO(name, size) \
+union { \
+        struct kfifo name; \
+        unsigned char name##kfifo_buffer[size + sizeof(struct kfifo)]; \
+}
+
+/**
+ * INIT_KFIFO - Initialize a kfifo declared by DECLARED_KFIFO
+ * @name: name of the declared kfifo datatype
+ * @size: size of the fifo buffer
+ */
+#define INIT_KFIFO(name) \
+        name = __kfifo_initializer(sizeof(name##kfifo_buffer) - \
+                                sizeof(struct kfifo), name##kfifo_buffer)
+
+/**
+ * DEFINE_KFIFO - macro to define and initialize a kfifo
+ * @name: name of the declared kfifo datatype
+ * @size: size of the fifo buffer
+ *
+ * Note: the macro can be used for global and local kfifo data type variables
+ * Note: the macro creates two objects:
+ *  A kfifo object with the given name and a buffer for the kfifo
+ *  object named name##kfifo_buffer
+ */
+#define DEFINE_KFIFO(name, size) \
+        unsigned char name##kfifo_buffer[size]; \
+        struct kfifo name = __kfifo_initializer(size, name##kfifo_buffer)
+
+#undef __kfifo_initializer
+
 extern void kfifo_init(struct kfifo *fifo, unsigned char *buffer,
                         unsigned int size);
 extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
@@ -71,6 +125,15 @@ static inline void kfifo_reset(struct kfifo *fifo)
 }
 
 /**
+ * kfifo_size - returns the size of the fifo in bytes
+ * @fifo: the fifo to be used.
+ */
+static inline __must_check unsigned int kfifo_size(struct kfifo *fifo)
+{
+        return fifo->size;
+}
+
+/**
  * kfifo_len - returns the number of used bytes in the FIFO
  * @fifo: the fifo to be used.
  */
@@ -84,6 +147,33 @@ static inline unsigned int kfifo_len(struct kfifo *fifo)
 }
 
 /**
+ * kfifo_is_empty - returns true if the fifo is empty
+ * @fifo: the fifo to be used.
+ */
+static inline __must_check int kfifo_is_empty(struct kfifo *fifo)
+{
+        return fifo->in == fifo->out;
+}
+
+/**
+ * kfifo_is_full - returns true if the fifo is full
+ * @fifo: the fifo to be used.
+ */
+static inline __must_check int kfifo_is_full(struct kfifo *fifo)
+{
+        return kfifo_len(fifo) == kfifo_size(fifo);
+}
+
+/**
+ * kfifo_avail - returns the number of bytes available in the FIFO
+ * @fifo: the fifo to be used.
+ */
+static inline __must_check unsigned int kfifo_avail(struct kfifo *fifo)
+{
+        return kfifo_size(fifo) - kfifo_len(fifo);
+}
+
+/**
  * kfifo_in_locked - puts some data into the FIFO using a spinlock for locking
  * @fifo: the fifo to be used.
  * @from: the data to be added.
@@ -133,8 +223,8 @@ static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
          * optimization: if the FIFO is empty, set the indices to 0
          * so we don't wrap the next time
          */
-        if (fifo->in == fifo->out)
-                fifo->in = fifo->out = 0;
+        if (kfifo_is_empty(fifo))
+                kfifo_reset(fifo);
 
         spin_unlock_irqrestore(lock, flags);