Man page 9 : bitmap_find_free_region

bitmap_find_free_region - find a contiguous aligned mem region

int bitmap_find_free_region(unsigned long *  bitmap , int  bits , int  order );

bitmap
    array of unsigned longs corresponding to the bitmap

bits
    number of bits in the bitmap

order
    region size (log base 2 of number of bits) to find

Find a region of free (zero) bits in a bitmap of bits bits and allocate them (set them to one). Only consider regions of length a power (order) of two, aligned to that power of two, which makes the search algorithm much faster.

Return the bit offset in bitmap of the allocated region, or -errno on failure.