linux-kernel - Re: [PATCH net-next v6 06/15] ethtool: netlink bitset handling

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Message-ID: <20190703143724.GD2250@nanopsycho>
Date:   Wed, 3 Jul 2019 16:37:24 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Michal Kubecek <mkubecek@...e.cz>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        John Linville <linville@...driver.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v6 06/15] ethtool: netlink bitset handling

Wed, Jul 03, 2019 at 03:44:57PM CEST, johannes@...solutions.net wrote:
>On Wed, 2019-07-03 at 13:49 +0200, Jiri Pirko wrote:
>> 
>> > +Value and mask must have length at least ETHTOOL_A_BITSET_SIZE bits rounded up
>> > +to a multiple of 32 bits. They consist of 32-bit words in host byte order,
>> 
>> Looks like the blocks are similar to NLA_BITFIELD32. Why don't you user
>> nested array of NLA_BITFIELD32 instead?
>
>That would seem kind of awkward to use, IMHO.
>
>Perhaps better to make some kind of generic "arbitrary size bitfield"
>attribute type?

Yep, I believe I was trying to make this point during bitfield32
discussion, failed apparently. So if we have "NLA_BITFIELD" with
arbitrary size, that sounds good to me.


>
>Not really sure we want the complexity with _LIST and _SIZE, since you
>should always be able to express it as _VALUE and _MASK, right?
>
>Trying to think how we should express this best - bitfield32 is just a
>mask/value struct, for arbitrary size I guess we *could* just make it
>kind of a binary with arbitrary length that must be a multiple of 2
>bytes (or 2 u32-bit-words?) and then the first half is the value and the
>second half is the mask? Some more validation would be nicer, but having
>a generic attribute that actually is nested is awkward too.
>
>johannes
>
>