On Fri, 9 Oct 2009 17:29:15 +0900 Akinobu Mita <akinobu.mita@xxxxxxxxx> wrote: > This introduces new bitmap functions: > > bitmap_set: Set specified bit area > bitmap_clear: Clear specified bit area > bitmap_find_next_zero_area: Find free bit area > > These are stolen from iommu helper. > > I changed the return value of bitmap_find_next_zero_area if there is > no zero area. > > find_next_zero_area in iommu helper: returns -1 > bitmap_find_next_zero_area: return >= bitmap size I'll plan to merge this patch into 2.6.32 so we can trickle all the other patches into subsystems in an orderly fashion. > +void bitmap_set(unsigned long *map, int i, int len) > +{ > + int end = i + len; > + > + while (i < end) { > + __set_bit(i, map); > + i++; > + } > +} This is really inefficient, isn't it? It's a pretty trivial matter to romp through memory 32 or 64 bits at a time. > +EXPORT_SYMBOL(bitmap_set); > + > +void bitmap_clear(unsigned long *map, int start, int nr) > +{ > + int end = start + nr; > + > + while (start < end) { > + __clear_bit(start, map); > + start++; > + } > +} > +EXPORT_SYMBOL(bitmap_clear); Ditto. > +unsigned long bitmap_find_next_zero_area(unsigned long *map, > + unsigned long size, > + unsigned long start, > + unsigned int nr, > + unsigned long align_mask) > +{ > + unsigned long index, end, i; > +again: > + index = find_next_zero_bit(map, size, start); > + > + /* Align allocation */ > + index = (index + align_mask) & ~align_mask; > + > + end = index + nr; > + if (end >= size) > + return end; > + i = find_next_bit(map, end, index); > + if (i < end) { > + start = i + 1; > + goto again; > + } > + return index; > +} > +EXPORT_SYMBOL(bitmap_find_next_zero_area); This needs documentation, please. It appears that `size' is the size of the bitmap and `nr' is the number of zeroed bits we're looking for, but an inattentive programmer could get those reversed. Also the semantics of `align_mask' could benefit from spelling out. Is the alignment with respect to memory boundaries or with respect to `map' or with respect to map+start or what? And why does align_mask exist at all? I was a bit surprised to see it there. In which scenarios will it be non-zero? -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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