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    SubjectPatch 1/23 - Bitmaps, Cpumasks and Nodemasks
    P1.bitmap_comment - Document bitmap.c bit model.
    Document the bitmap bit model, including handling of unused bits,
    and operation preconditions and postconditions.

    Index: 2.6.5.bitmap/lib/bitmap.c
    ===================================================================
    --- 2.6.5.bitmap.orig/lib/bitmap.c 2004-04-05 02:00:15.000000000 -0700
    +++ 2.6.5.bitmap/lib/bitmap.c 2004-04-05 02:50:25.000000000 -0700
    @@ -12,6 +12,26 @@
    #include <asm/bitops.h>
    #include <asm/uaccess.h>

    +/*
    + * bitmaps provide an array of bits, implemented using an an
    + * array of unsigned longs. The number of valid bits in a
    + * given bitmap need not be an exact multiple of BITS_PER_LONG.
    + *
    + * The possible unused bits in the last, partially used word
    + * of a bitmap are 'don't care'. The implementation makes
    + * no particular effort to keep them zero. It ensures that
    + * their value will not affect the results of any operation.
    + * The bitmap operations that return Boolean (bitmap_empty,
    + * for example) or scalar (bitmap_weight, for example) results
    + * carefully filter out these unused bits from impacting their
    + * results.
    + *
    + * Except for bitmap_complement, these operations hold to a
    + * slightly stronger rule: if you don't input any bitmaps to
    + * these ops that have some unused bits set, then they won't
    + * output any set unused bits in output bitmaps.
    + */
    +
    #define MAX_BITMAP_BITS 512U /* for ia64 NR_CPUS maximum */

    int bitmap_empty(const unsigned long *bitmap, int bits)

    --
    I won't rest till it's the best ...
    Programmer, Linux Scalability
    Paul Jackson <pj@sgi.com> 1.650.933.1373
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