Messages in this thread | | | Subject | Re: bitmap API consistency | From | Andy Shevchenko <> | Date | Wed, 24 May 2017 15:43:25 +0300 |
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On Wed, 2017-05-24 at 14:38 +0200, Rasmus Villemoes wrote: > On 24 May 2017 at 14:11, Andy Shevchenko > <andriy.shevchenko@linux.intel.com> wrote: > > Hi! > > > > Surprisingly discovered today that bitmap API is not consistent in > > some > > cases (at least one I found recently). > > > > bitmap_fill() sets area of bits in a bitmap. > > bitmap_zero() clears them. > > > > However, if _fill() does something sane, _zero() clears _all_ bits > > up to > > word size (long). > > > > I think it should be fixed to be consistent with _fill() variant. > > What do you want it to do?
Based on my vision and your answer below, thanks for it, I think we need to a) make _fill() to fill entire _aligned_ area b) update comments in the header and documentation, if needed, to specify that _fill() / _zero() operates on aligned to word size area, while _set() and _clear() do exact amount of bits.
> It always acts on whole words, so the last > word must be set to something. One might as well say that _zero and > _fill are consistent in that they both set the bits beyond nbits in > the last word to 0. > > If anything, I'd change bitmap_fill to do a memset(0xff) of the entire > region. There used to be bugs where some of the bitmap_* functions > didn't actually ignore the trailing bits, making it somewhat important > that they were always 0, but I think they're fixed now. > > Note that if one wants a guarantee that the trailing bits are not > touched at all, the APIs to use are bitmap_{set, clear}(dst, 0, > count). bitmap_{zero,fill} assumes that nbits is the total size of the > bitmap (i.e. that the user will never care about bits beyond nbits). > Maybe a few comments could be added somewhere. > > Rasmus
-- Andy Shevchenko <andriy.shevchenko@linux.intel.com> Intel Finland Oy
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