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    SubjectRe: PATCH [1/3] drivers/input/xpad.c: Improve Xbox 360 wireless support and add sysfs interface
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    On Mon, Mar 2, 2009 at 4:35 PM, Andrew Morton <akpm@linux-foundation.org> wrote:
    >
    > OK.  I think.
    >
    > - This approach will require a large number of edits each time an
    >  attribute is added/removed.
    >
    > - otoh, removing nasty macros is always nice.
    >
    > - This approach will generate slower code (which doesn't matter
    >  here).
    >
    > - Was it demonstrated that this approach generates less code?
    >

    It should generate less code, as compared to having two functions
    (show and store) per attribute, in which each function has about 4
    lines and a local variable for the store functions (which is there for
    type validation). For both show and store functions, there still has
    to be code to get to the struct usb_xpad instance.

    As I was coding this interface, I found myself wishing for a
    macro-based system like module parameters have. For example, it would
    be nice to be able to do something like the following:

    DECLARE_SYSFS_INTERFACE(&xpad->dead_zone, uint, &check_dead_zone);

    which would create the needed show/store functions that worked with an
    unsigned int. The check_dead_zone function would be a validator
    function inside the module that would check the validity on a
    user-supplied value on store (in this case, to be sure it was at least
    1024 below the stick limit) and return an error code if the value were
    out of range. Yes, the validator would be an extra function call, but
    this code doesn't run in an interrupt context, so the benefit of being
    able to centralize the functionality and simplify drivers might be
    worth the extra overhead.

    Mike
    --
    Mike Murphy
    Ph.D. Candidate and NSF Graduate Research Fellow
    Clemson University School of Computing
    120 McAdams Hall
    Clemson, SC 29634-0974 USA
    Tel: +1 864.656.2838 Fax: +1 864.656.0145
    http://cirg.cs.clemson.edu/~mamurph
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