Messages in this thread | | | Date | Wed, 13 Jul 2022 13:42:17 -0700 | From | Yury Norov <> | Subject | Re: [PATCH 3/6] bitops: bitmap helper to set variable length values |
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On Wed, Jul 13, 2022 at 10:14:24PM +0200, Andy Shevchenko wrote: > On Wed, Jul 13, 2022 at 9:44 PM Yury Norov <yury.norov@gmail.com> wrote: > > On Wed, Jul 13, 2022 at 09:10:33PM +0200, Andy Shevchenko wrote: > > > On Wed, Jul 13, 2022 at 8:56 PM Yury Norov <yury.norov@gmail.com> wrote: > > > > On Wed, Jul 13, 2022 at 06:31:59PM +0200, Sebastian Fricke wrote: > > > > > > ... > > > > > > > I'd suggest you to try implementing > > > > bitmap_copy_from(dst, src, dst_off, len) > > > > or even > > > > bitmap_copy_from(dst, dst_off, src, src_off, len) > > > > if you expect that you'll need more flexibility in the future. > > > > > > Do you think it would be useful? > > > > > > We have bitmap_replace() & bitmap_remap(). Wouldn't that be enough? > > > > bitmap_replace and bitmap_remap have no an 'offset' parameter. > > True. > > But then it's a bit too generic to have this src_off, no?
That's why I said:
> > > > if you expect that you'll need more flexibility in the future.
My preferred option is bitmap_copy_from(dst, src, dst_off, len).
> I would rather expect for asymmetrical bitmaps that the other side > will be either one of the fixed width types (it makes sense to have > for 32- or 64-bit arguments.
Look at patch #6 - it copies 1,4,5,9,10,32,37... - pretty much a random number number of bits.
> When you have a source bitmap of x bits and you would like to copy it > into a y-bit one, I would think that either you have a small amount of > bits in x anyway, or x is a full-sized bitmap (same order as y).
It sounds like a speculation to me. Why shouldn't we let people to copy with an offset any number of bits?
> Also > keep in mind that granularity is long, so less than long it makes no > sense. > > bitmap_copy_from_T(unsigned long *map, start, len, T src), > > where T is type, start is the offset in map, len is the amount of bits > from src starting from 0. That's what is required in most of the cases > I believe.
But not in Sebastian's case, according to patch #6.
Thanks, Yury
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