Re: [PATCH v2 2/3] lib: Introduce 2 bit ops api: all_is_bit_{one,zero}

[hejianet]

Thanksï I will add it in next verison
B.R.
Justin

å 11/19/15 4:40 PM, xinhui åé:
> hi, jia
>     Nice patch. But I have one minor question. see inline comments.
>
> On 2015/11/19 14:48, Jia He wrote:
> > This patch introduces 2 lightweight bit api.
> > all_bit_is_zero return 1 if the bit string is all zero.
> > The addr is the start address, the size is the bit size of the bit 
> > string.
> > all_bit_is_one is the opposite.
> >
> > Signed-off-by: Jia He <hejianet@xxxxxxxxx>
> > ---
> >   lib/find_bit.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 50 insertions(+)
> >
> > diff --git a/lib/find_bit.c b/lib/find_bit.c
> > index 18072ea..1d56d8d 100644
> > --- a/lib/find_bit.c
> > +++ b/lib/find_bit.c
> > @@ -131,6 +131,56 @@ unsigned long find_last_bit(const unsigned long 
> > *addr, unsigned long size)
> >   EXPORT_SYMBOL(find_last_bit);
> >   #endif
> >
> > +#ifndef all_bit_is_zero
> > +/*
> > + * return val: 1 means all bit is zero
> > + */
> > +unsigned int all_bit_is_zero(const unsigned long *addr, unsigned size)
> > +{
>  Seems better that size should be type of "unsigned long". Otherwise 
> I'm afraid when we compare idx * BITS_PER_LONG with size, there might 
> be overflow issue.
>
> > +    unsigned long idx;
> > +    unsigned long mask = size;
> > +
> > +    if (unlikely(size == 0))
> > +        return 1;
> > +
> > +    if (size > BITS_PER_LONG) {
> > +        for (idx = 0; idx * BITS_PER_LONG < size; idx++)
> > +            if (addr[idx])
> > +                return 0;
> > +
> > +        mask = size - (idx - 1) * BITS_PER_LONG;
> > +    }
> > +
> > +    return !(*addr & BITMAP_LAST_WORD_MASK(mask));
> > +}
> > +EXPORT_SYMBOL(all_bit_is_zero);
> > +#endif
> > +
> > +#ifndef all_bit_is_one
> > +/*
> > + * return val: 1 means all bit is one
> > + */
> > +unsigned int all_bit_is_one(const unsigned long *addr, unsigned size)
> > +{
> this argc of size should be type of "unsigned long", too.
>
> thanks
> xinhui
>
> > +    unsigned long idx;
> > +    unsigned long mask = size;
> > +
> > +    if (unlikely(size == 0))
> > +        return 1;
> > +
> > +    if (size > BITS_PER_LONG) {
> > +        for (idx = 0; idx * BITS_PER_LONG < size; idx++)
> > +            if (~addr[idx])
> > +                return 0;
> > +
> > +        mask = size - (idx - 1) * BITS_PER_LONG;
> > +    }
> > +
> > +    return !(~(*addr) & BITMAP_LAST_WORD_MASK(mask));
> > +}
> > +EXPORT_SYMBOL(all_bit_is_one);
> > +#endif
> > +
> >   #ifdef __BIG_ENDIAN
> >
> >   /* include/linux/byteorder does not support "unsigned long" type */
>
> --
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