From 45465487897a1c6d508b14b904dc5777f7ec7e04 Mon Sep 17 00:00:00 2001 From: Stefani Seibold Date: Mon, 21 Dec 2009 14:37:26 -0800 Subject: 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 Acked-by: Greg Kroah-Hartman Acked-by: Mauro Carvalho Chehab Acked-by: Andi Kleen Acked-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/media/video/meye.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/media/video/meye.h') diff --git a/drivers/media/video/meye.h b/drivers/media/video/meye.h index 5f70a106ba2b..1321ad5d6597 100644 --- a/drivers/media/video/meye.h +++ b/drivers/media/video/meye.h @@ -303,9 +303,9 @@ struct meye { struct meye_grab_buffer grab_buffer[MEYE_MAX_BUFNBRS]; int vma_use_count[MEYE_MAX_BUFNBRS]; /* mmap count */ struct mutex lock; /* mutex for open/mmap... */ - struct kfifo *grabq; /* queue for buffers to be grabbed */ + struct kfifo grabq; /* queue for buffers to be grabbed */ spinlock_t grabq_lock; /* lock protecting the queue */ - struct kfifo *doneq; /* queue for grabbed buffers */ + struct kfifo doneq; /* queue for grabbed buffers */ spinlock_t doneq_lock; /* lock protecting the queue */ wait_queue_head_t proc_list; /* wait queue */ struct video_device *video_dev; /* video device parameters */ -- cgit v1.2.3