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    SubjectRe: [PATCH net-next v7 01/19] lib/bitmap.c: conversion routines to/from u32 array
    On Sun,  7 Feb 2016 17:08:45 -0800 David Decotigny <ddecotig@gmail.com> wrote:

    > From: David Decotigny <decot@googlers.com>
    >
    > Aimed at transferring bitmaps to/from user-space in a 32/64-bit agnostic
    > way.
    >
    > Tested:
    > unit tests (next patch) on qemu i386, x86_64, ppc, ppc64 BE and LE,
    > ARM.
    >
    > @@ -1060,6 +1062,90 @@ int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order)
    > EXPORT_SYMBOL(bitmap_allocate_region);
    >
    > /**
    > + * bitmap_from_u32array - copy the contents of a u32 array of bits to bitmap
    > + * @bitmap: array of unsigned longs, the destination bitmap, non NULL
    > + * @nbits: number of bits in @bitmap
    > + * @buf: array of u32 (in host byte order), the source bitmap, non NULL
    > + * @nwords: number of u32 words in @buf
    > + *
    > + * copy min(nbits, 32*nwords) bits from @buf to @bitmap, remaining
    > + * bits between nword and nbits in @bitmap (if any) are cleared. In
    > + * last word of @bitmap, the bits beyond nbits (if any) are kept
    > + * unchanged.
    > + */

    This will leave the caller not knowing how many valid bits are actually
    present in the resulting bitmap. To determine that, the caller will
    need to perform (duplicated) math on `nbits' and `nwords'.

    > +void bitmap_from_u32array(unsigned long *bitmap, unsigned int nbits,
    > + const u32 *buf, unsigned int nwords)

    So how about we make this return the number of valid bits in *bitmap?

    > +/**
    > + * bitmap_to_u32array - copy the contents of bitmap to a u32 array of bits
    > + * @buf: array of u32 (in host byte order), the dest bitmap, non NULL
    > + * @nwords: number of u32 words in @buf
    > + * @bitmap: array of unsigned longs, the source bitmap, non NULL
    > + * @nbits: number of bits in @bitmap
    > + *
    > + * copy min(nbits, 32*nwords) bits from @bitmap to @buf. Remaining
    > + * bits after nbits in @buf (if any) are cleared.
    > + */
    > +void bitmap_to_u32array(u32 *buf, unsigned int nwords,
    > + const unsigned long *bitmap, unsigned int nbits)

    Ditto.


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