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    Subject[PATCH 27/35] cpumask: to_cpumask()
    There are times when we really want a static cpumask.  Yet we don't
    want to expose the struct cpumask definition, to avoid casual on-stack
    usage and assignment.

    So this macro allows you to do DECLARE_BITMAP(map, CONFIG_NR_CPUS); then use
    to_cpumask() to turn it into a cpumask as needed.

    Ugly? Yes, but as we move to fewer static cpumasks these calls vanish.

    From: Rusty Russell <rusty@rustcorp.com.au>
    Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    Signed-off-by: Mike Travis <travis@sgi.com>
    ---
    include/linux/cpumask.h | 14 ++++++++++++++
    1 file changed, 14 insertions(+)
    --- linux-2.6.28.orig/include/linux/cpumask.h
    +++ linux-2.6.28/include/linux/cpumask.h
    @@ -57,6 +57,9 @@
    * CPU_MASK_NONE Initializer - no bits set
    * unsigned long *cpumask_bits(mask) Array of unsigned long's in mask
    *
    + * struct cpumask *to_cpumask(const unsigned long[])
    + * Convert a bitmap to a cpumask.
    + *
    * ------------------------------------------------------------------------
    *
    * int cpumask_scnprintf(buf, len, mask) Format cpumask for printing
    @@ -362,6 +365,17 @@ static inline void cpumask_copy(struct c
    #define cpumask_any(srcp) cpumask_first(srcp)
    #define cpumask_any_and(mask1, mask2) cpumask_first_and((mask1), (mask2))

    +/* Used for static bitmaps of CONFIG_NR_CPUS bits. Must be a constant to use
    + * as an initializer. */
    +#define to_cpumask(bitmap) \
    + ((struct cpumask *)(1 ? (bitmap) \
    + : (void *)sizeof(__check_is_bitmap(bitmap))))
    +
    +static inline int __check_is_bitmap(const unsigned long *bitmap)
    +{
    + return 1;
    +}
    +
    /*
    * Special-case data structure for "single bit set only" constant CPU masks.
    *
    --


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