Eric Lee / smarc-fsl-linux-kernel

31 Dec, 2009

1 commit

  • 75c85a0bc   libsrp: fix compile failure ... Browse Code »

    commit 45465487897a1c6d508b14b904dc5777f7ec7e04 ("kfifo: move struct
    kfifo in place") caused a compile failure in ibmvscsitgt.c because it
    changed a pointer to kfifo in the libsrp.h structure to a direct
    inclusion without including .

    The fix is simple, just add the include, but how did this happen? This
    change, introduced at -rc2, hardly looks like a bug fix, and it clearly
    didn't go through linux-next, which would have picked up this compile
    failure (it only occurs on ppc because of the ibm virtual scsi target).

    [ Apparently all of -mm wasn't in linux-next.. ]

    Signed-off-by: James Bottomley
    Signed-off-by: Linus Torvalds

    James Bottomley
     

23 Dec, 2009

1 commit

  • 454654878   kfifo: move struct kfifo in place ... Browse Code »

    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

    Stefani Seibold
     

13 Oct, 2007

1 commit

03 Dec, 2006

1 commit