kfifo: move struct kfifo in place

This is a new generic kernel FIFO implementation.

The current kernel fifo API is not very widely used, because it has to
many constrains.  Only 17 files in the current 2.6.31-rc5 used it.
FIFO's are like list's a very basic thing and a kfifo API which handles
the most use case would save a lot of development time and memory
resources.

I think this are the reasons why kfifo is not in use:

 - The API is to simple, important functions are missing
 - A fifo can be only allocated dynamically
 - There is a requirement of a spinlock whether you need it or not
 - There is no support for data records inside a fifo

So I decided to extend the kfifo in a more generic way without blowing up
the API to much.  The new API has the following benefits:

 - Generic usage: For kernel internal use and/or device driver.
 - Provide an API for the most use case.
 - Slim API: The whole API provides 25 functions.
 - Linux style habit.
 - DECLARE_KFIFO, DEFINE_KFIFO and INIT_KFIFO Macros
 - Direct copy_to_user from the fifo and copy_from_user into the fifo.
 - The kfifo itself is an in place member of the using data structure, this save an
   indirection access and does not waste the kernel allocator.
 - Lockless access: if only one reader and one writer is active on the fifo,
   which is the common use case, no additional locking is necessary.
 - Remove spinlock - give the user the freedom of choice what kind of locking to use if
   one is required.
 - Ability to handle records. Three type of records are supported:
   - Variable length records between 0-255 bytes, with a record size
     field of 1 bytes.
   - Variable length records between 0-65535 bytes, with a record size
     field of 2 bytes.
   - Fixed size records, which no record size field.
 - Preserve memory resource.
 - Performance!
 - Easy to use!

This patch:

Since most users want to have the kfifo as part of another object,
reorganize the code to allow including struct kfifo in another data
structure.  This requires changing the kfifo_alloc and kfifo_init
prototypes so that we pass an existing kfifo pointer into them.  This
patch changes the implementation and all existing users.

[akpm@linux-foundation.org: fix warning]
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>

drivers/net/wireless/libertas/cmd.c

@@ -1365,7 +1365,7 @@ static void lbs_send_confirmsleep(struct lbs_private *priv)
 	priv->dnld_sent = DNLD_RES_RECEIVED;
 
 	/* If nothing to do, go back to sleep (?) */
-	if (!__kfifo_len(priv->event_fifo) && !priv->resp_len[priv->resp_idx])
+	if (!__kfifo_len(&priv->event_fifo) && !priv->resp_len[priv->resp_idx])
 		priv->psstate = PS_STATE_SLEEP;
 
 	spin_unlock_irqrestore(&priv->driver_lock, flags);
@@ -1439,7 +1439,7 @@ void lbs_ps_confirm_sleep(struct lbs_private *priv)
 	}
 
 	/* Pending events or command responses? */
-	if (__kfifo_len(priv->event_fifo) || priv->resp_len[priv->resp_idx]) {
+	if (__kfifo_len(&priv->event_fifo) || priv->resp_len[priv->resp_idx]) {
 		allowed = 0;
 		lbs_deb_host("pending events or command responses\n");
 	}