Date:	Mon, 16 Nov 2009 13:04:25 +0100
From:	Stefani Seibold <stefani@...bold.net>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Andi Kleen <andi@...stfloor.org>,
	Amerigo Wang <xiyou.wangcong@...il.com>,
	Joe Perches <joe@...ches.com>
Subject: Re: [PATCH 5/7] 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@...bold.net>
Acked-by: Greg Kroah-Hartman <gregkh@...e.de>
Acked-by: Mauro Carvalho Chehab <mchehab@...hat.com>
Acked-by: Andi Kleen <ak@...ux.intel.com>
Acked-by: Arnd Bergmann <arnd@...db.de>
---
 kfifo.h |   91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 89 insertions(+), 2 deletions(-)

diff -u -N -r kfifo4/include/linux/kfifo.h kfifo5/include/linux/kfifo.h
--- kfifo4/include/linux/kfifo.h        2009-10-19 21:21:36.000000000 +0200
+++ kfifo5/include/linux/kfifo.h        2009-10-19 21:25:25.000000000 +0200
@@ -51,6 +51,57 @@
        unsigned int out;       /* data is extracted from off. (out % size) */
 };
 
+/*
+ * Macros for declaration and initialization of the kfifo datatype
+ */
+
+#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)
+
 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 +122,15 @@
 }
 
 /**
+ * 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 +144,33 @@
 }
 
 /**
+ * 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 +220,8 @@
         * 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);
 



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