linux-kernel - Re: [PATCH v2 1/5] bitops: Introduce find_next_andnot

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Date:   Fri, 19 Aug 2022 11:34:01 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     netdev <netdev@...r.kernel.org>,
        "open list:HFI1 DRIVER" <linux-rdma@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Mel Gorman <mgorman@...e.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Tony Luck <tony.luck@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Gal Pressman <gal@...dia.com>, Tariq Toukan <tariqt@...dia.com>
Subject: Re: [PATCH v2 1/5] bitops: Introduce find_next_andnot_bit()

On 18/08/22 22:04, Andy Shevchenko wrote:
> On Thu, Aug 18, 2022 at 8:18 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>> On Thu, 18 Aug 2022 17:26:43 +0100
>> Valentin Schneider <vschneid@...hat.com> wrote:
>>
>> > How about:
>>
>> >
>> >   find the next set bit in (*addr1 & ~*addr2)
>>
>> I understand the above better. But to convert that into English, we could
>> say:
>>
>>
>>   Find the next bit in *addr1 excluding all the bits in *addr2.
>>
>> or
>>
>>   Find the next bit in *addr1 that is not set in *addr2.
>
> With this explanation I'm wondering how different this is to
> bitmap_bitremap(), with adjusting to using an inverted mask. If they
> have something in common, perhaps make them in the same namespace with
> similar naming convention?
>

I'm trying to wrap my head around the whole remap thing, IIUC we could have
something like remap *addr1 to ~*addr2 and stop rather than continue with a
wraparound, but that really feels like shoehorning.

> --
> With Best Regards,
> Andy Shevchenko