netdev - Re: [PATCH net-next 2/7] net: nexthop: Add NHA_OP

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Message-ID: <20240228071601.7117217c@kernel.org>
Date: Wed, 28 Feb 2024 07:16:01 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Petr Machata <petrm@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 <netdev@...r.kernel.org>, Ido Schimmel <idosch@...dia.com>, David Ahern
 <dsahern@...nel.org>, <mlxsw@...dia.com>
Subject: Re: [PATCH net-next 2/7] net: nexthop: Add NHA_OP_FLAGS

On Wed, 28 Feb 2024 06:48:59 -0800 Jakub Kicinski wrote:
> > But also I don't know what will be useful in the
> > future. It would be silly to have to add another flags attribute as
> > bitfield because this time we actually care about toggling single bits
> > of an object.  
> 
> IDK how you can do RMW on operation flags, that only makes sense if
> you're modifying something. Besides you're not using BITFIELD right,
> you're ignoring the mask completely now.

Let me rephrase this a bit since I've had my coffee now :)
BITFILED is designed to do:

	object->flags = object->flags & ~bf->mask | bf->flags;

since there's no object, there's nothing to & the mask with.
Plus if we do have some object flags at some point, chances 
are we'd want the uAPI flags to mirror the recorded object flags
so that we don't have to translate bit positions, so new attr
will be cleaner.

That's just in the way of clarifying my thinking, your call..