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>

1 files changed, 8 insertions, 10 deletions

diff --git a/drivers/platform/x86/fujitsu-laptop.c b/drivers/platform/x86/fujitsu-laptop.c
index bcd4ba8be7db..f999fba0e25e 100644
--- a/drivers/platform/x86/fujitsu-laptop.c
+++ b/drivers/platform/x86/fujitsu-laptop.c
@@ -164,7 +164,7 @@ struct fujitsu_hotkey_t {
 	struct input_dev *input;
 	char phys[32];
 	struct platform_device *pf_device;
-	struct kfifo *fifo;
+	struct kfifo fifo;
 	spinlock_t fifo_lock;
 	int rfkill_supported;
 	int rfkill_state;
@@ -824,12 +824,10 @@ static int acpi_fujitsu_hotkey_add(struct acpi_device *device)
 
 	/* kfifo */
 	spin_lock_init(&fujitsu_hotkey->fifo_lock);
-	fujitsu_hotkey->fifo =
-	    kfifo_alloc(RINGBUFFERSIZE * sizeof(int), GFP_KERNEL,
-			&fujitsu_hotkey->fifo_lock);
-	if (IS_ERR(fujitsu_hotkey->fifo)) {
+	error = kfifo_alloc(&fujitsu_hotkey->fifo, RINGBUFFERSIZE * sizeof(int),
+			GFP_KERNEL, &fujitsu_hotkey->fifo_lock);
+	if (error) {
 		printk(KERN_ERR "kfifo_alloc failed\n");
-		error = PTR_ERR(fujitsu_hotkey->fifo);
 		goto err_stop;
 	}
 
@@ -934,7 +932,7 @@ err_unregister_input_dev:
 err_free_input_dev:
 	input_free_device(input);
 err_free_fifo:
-	kfifo_free(fujitsu_hotkey->fifo);
+	kfifo_free(&fujitsu_hotkey->fifo);
 err_stop:
 	return result;
 }
@@ -956,7 +954,7 @@ static int acpi_fujitsu_hotkey_remove(struct acpi_device *device, int type)
 
 	input_free_device(input);
 
-	kfifo_free(fujitsu_hotkey->fifo);
+	kfifo_free(&fujitsu_hotkey->fifo);
 
 	fujitsu_hotkey->acpi_handle = NULL;
 
@@ -1008,7 +1006,7 @@ static void acpi_fujitsu_hotkey_notify(struct acpi_device *device, u32 event)
 				vdbg_printk(FUJLAPTOP_DBG_TRACE,
 					"Push keycode into ringbuffer [%d]\n",
 					keycode);
-				status = kfifo_put(fujitsu_hotkey->fifo,
+				status = kfifo_put(&fujitsu_hotkey->fifo,
 						   (unsigned char *)&keycode,
 						   sizeof(keycode));
 				if (status != sizeof(keycode)) {
@@ -1022,7 +1020,7 @@ static void acpi_fujitsu_hotkey_notify(struct acpi_device *device, u32 event)
 			} else if (keycode == 0) {
 				while ((status =
 					kfifo_get
-					(fujitsu_hotkey->fifo, (unsigned char *)
+					(&fujitsu_hotkey->fifo, (unsigned char *)
 					 &keycode_r,
 					 sizeof
 					 (keycode_r))) == sizeof(keycode_r)) {