linux-kernel - Re: [PATCH net-next 0/4] netlink: add 'bitmap' attribute type and API

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Message-ID: <20220721111318.1b180762@kernel.org>
Date:   Thu, 21 Jul 2022 11:13:18 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 0/4] netlink: add 'bitmap' attribute type and
 API

On Thu, 21 Jul 2022 17:59:46 +0200 Alexander Lobakin wrote:
> BTW, Ethtool bitsets provide similar functionality, but it operates
> with u32s (u64 is more convenient and optimal on most platforms) and
> Netlink bitmaps is a generic interface providing policies and data
> verification (Ethtool bitsets are declared simply as %NLA_BINARY),
> generic getters/setters etc.

Are you saying we don't need the other two features ethtool bitmaps
provide? Masking and compact vs named representations?

I think that straight up bitmap with a fixed word is awkward and leads
to too much boilerplate code. People will avoid using it. What about
implementing a bigint type instead? Needing more than 64b is extremely
rare, so in 99% of the cases the code outside of parsing can keep using
its u8/u16/u32.