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charset=us-ascii Content-Disposition: inline In-Reply-To: <20240819142406.339084-2-mathieu.desnoyers@efficios.com> On Mon, Aug 19, 2024 at 04:24:02PM +0200, Mathieu Desnoyers wrote: > Allow finding the first, next, or nth bit within two input bitmasks > which is zero in both masks. > > Allow fiding the first bit within two input bitmasks which is set in > first mask and cleared in the second mask. find_next_andnot_bit and > find_nth_andnot_bit already exist, so find the first bit appears to be > missing. > > Signed-off-by: Mathieu Desnoyers > Cc: Yury Norov > Cc: Rasmus Villemoes > --- > include/linux/find.h | 122 +++++++++++++++++++++++++++++++++++++++++-- > lib/find_bit.c | 42 +++++++++++++++ > 2 files changed, 160 insertions(+), 4 deletions(-) > > diff --git a/include/linux/find.h b/include/linux/find.h > index 5dfca4225fef..6b2377006b22 100644 > --- a/include/linux/find.h > +++ b/include/linux/find.h > @@ -14,6 +14,8 @@ unsigned long _find_next_and_bit(const unsigned long *addr1, const unsigned long > unsigned long nbits, unsigned long start); > unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned long *addr2, > unsigned long nbits, unsigned long start); > +unsigned long _find_next_notandnot_bit(const unsigned long *addr1, const unsigned long *addr2, > + unsigned long nbits, unsigned long start); > unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2, > unsigned long nbits, unsigned long start); > unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits, > @@ -24,11 +26,17 @@ unsigned long __find_nth_and_bit(const unsigned long *addr1, const unsigned long > unsigned long size, unsigned long n); > unsigned long __find_nth_andnot_bit(const unsigned long *addr1, const unsigned long *addr2, > unsigned long size, unsigned long n); > +unsigned long __find_nth_notandnot_bit(const unsigned long *addr1, const unsigned long *addr2, > + unsigned long size, unsigned long n); > unsigned long __find_nth_and_andnot_bit(const unsigned long *addr1, const unsigned long *addr2, > const unsigned long *addr3, unsigned long size, > unsigned long n); > extern unsigned long _find_first_and_bit(const unsigned long *addr1, > const unsigned long *addr2, unsigned long size); > +extern unsigned long _find_first_andnot_bit(const unsigned long *addr1, > + const unsigned long *addr2, unsigned long size); > +extern unsigned long _find_first_notandnot_bit(const unsigned long *addr1, > + const unsigned long *addr2, unsigned long size); > unsigned long _find_first_and_and_bit(const unsigned long *addr1, const unsigned long *addr2, > const unsigned long *addr3, unsigned long size); > extern unsigned long _find_first_zero_bit(const unsigned long *addr, unsigned long size); > @@ -102,15 +110,14 @@ unsigned long find_next_and_bit(const unsigned long *addr1, > > #ifndef find_next_andnot_bit > /** > - * find_next_andnot_bit - find the next set bit in *addr1 excluding all the bits > - * in *addr2 > + * find_next_andnot_bit - find the next set bit in *addr1, cleared in *addr2 > * @addr1: The first address to base the search on > * @addr2: The second address to base the search on > * @size: The bitmap size in bits > * @offset: The bitnumber to start searching at > * > - * Returns the bit number for the next set bit > - * If no bits are set, returns @size. > + * Returns the bit number for the next bit set in *addr1, cleared in *addr2. > + * If no such bits are found, returns @size. Can you split rewording of existing comments out to a separate patch please? > */ > static inline > unsigned long find_next_andnot_bit(const unsigned long *addr1, > @@ -131,6 +138,36 @@ unsigned long find_next_andnot_bit(const unsigned long *addr1, > } > #endif > > +#ifndef find_next_notandnot_bit Don't protect new functions. This is only for those having arch implementation, and it's only armv7 now. > +/** > + * find_next_notandnot_bit - find the next bit cleared in both *addr1 and *addr2 > + * @addr1: The first address to base the search on > + * @addr2: The second address to base the search on > + * @size: The bitmap size in bits > + * @offset: The bitnumber to start searching at > + * > + * Returns the bit number for the next bit cleared in both *addr1 and *addr2. > + * If no such bits are found, returns @size. > + */ > +static inline > +unsigned long find_next_notandnot_bit(const unsigned long *addr1, > + const unsigned long *addr2, unsigned long size, > + unsigned long offset) > +{ > + if (small_const_nbits(size)) { > + unsigned long val; > + > + if (unlikely(offset >= size)) > + return size; > + > + val = (~*addr1) & (~*addr2) & GENMASK(size - 1, offset); > + return val ? __ffs(val) : size; > + } > + > + return _find_next_notandnot_bit(addr1, addr2, size, offset); > +} > +#endif > + It's not said explicitly, but some naming conventions exist around bitmap searching. If you're looking for a clear (unset) bit in a mask, you'd use a 'zero' modifier. We have only 2 such functions now: find_{first,next}_zero_bit, both taking one bitmap. I think it's time to extend this rule for many bitmaps and write down the naming rules. With the following, the find_next_notandnot_bit() should be named like; find_next_zero_and_bit(). It's not perfect, but still sounds better to me than 'notandnot' thing. If we search for a set bit in bitmap, we use find_first or find_next prefixes: - find_first_bit; - find_next_bit. If we'd like to pass an additional bitmap to AND, OR or XOR with the 1st bitmap, we provide as corresponding logical operation as suffix(es): - find_first_and_bit(b1, b2) : b1 & b2; - find _next_and_or_bit(b1, b2, b3) : b1 & b2 | b3. If additional bitmap must be inverted, we provide a 'not' after the corresponding logical operation: - find_first_andnot_bit(b1, b2) : b1 & ~b2; - find _next_and_ornot_bit(b1, b2, b3) : b1 & b2 | ~b3. If all bitmaps have to be inverted, or in other words, we are looking for an unset bit in a bitmap or a combination of bitmaps, we provide a 'zero' prefix in the function name: - find_next_zero_bit; - find_next_zero_and_bit; - find_next_zero_and_or_bit; Functions having 'zero' prefix should not negate bitmaps (should not have 'not' in names) because of commutative property. For example, find_next_zero_andnot_bit(), which is ~b1 & ~(~b2) is redundant because it's the same as find_next_andnot_bit() : b2 & ~b1. Iterators over unset bits in bitmap(s) (those based on 'zero' search functions) should have a 'clear' prefix in the name: - for_each_clear_bit; - for_each_clear_bit_from; I should probably put the above on top of the file... Thanks, Yury