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authorStefani Seibold <stefani@seibold.net>2009-12-22 01:37:26 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-23 01:17:55 +0300
commit45465487897a1c6d508b14b904dc5777f7ec7e04 (patch)
tree935c8dae68dc793ff2f795d57cf027531475cd53 /include/linux/kfifo.h
parent2ec91eec47f713e3d158ba5b28a24a85a2cf3650 (diff)
downloadlinux-45465487897a1c6d508b14b904dc5777f7ec7e04.tar.xz
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>
Diffstat (limited to 'include/linux/kfifo.h')
-rw-r--r--include/linux/kfifo.h11
1 files changed, 6 insertions, 5 deletions
diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index ad6bdf5a5970..c3f8d82efd34 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -1,6 +1,7 @@
/*
- * A simple kernel FIFO implementation.
+ * A generic kernel FIFO implementation.
*
+ * Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
* Copyright (C) 2004 Stelian Pop <stelian@popies.net>
*
* This program is free software; you can redistribute it and/or modify
@@ -32,10 +33,10 @@ struct kfifo {
spinlock_t *lock; /* protects concurrent modifications */
};
-extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
- gfp_t gfp_mask, spinlock_t *lock);
-extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask,
- spinlock_t *lock);
+extern void kfifo_init(struct kfifo *fifo, unsigned char *buffer,
+ unsigned int size, spinlock_t *lock);
+extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
+ gfp_t gfp_mask, spinlock_t *lock);
extern void kfifo_free(struct kfifo *fifo);
extern unsigned int __kfifo_put(struct kfifo *fifo,
const unsigned char *buffer, unsigned int len);