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authorStefani Seibold <stefani@seibold.net>2009-12-21 14:37:26 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-12-22 14:17:55 -0800
commit45465487897a1c6d508b14b904dc5777f7ec7e04 (patch)
tree935c8dae68dc793ff2f795d57cf027531475cd53 /drivers/media/video/meye.h
parent2ec91eec47f713e3d158ba5b28a24a85a2cf3650 (diff)
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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 'drivers/media/video/meye.h')
-rw-r--r--drivers/media/video/meye.h4
1 files changed, 2 insertions, 2 deletions
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 */