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Date: Thu, 11 Apr 2024 07:47:09 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Alexander Lobakin <aleksander.lobakin@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>, Eric Dumazet
 <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, David Ahern
 <dsahern@kernel.org>, Xuan Zhuo <xuanzhuo@linux.alibaba.com>, Andrew Lunn
 <andrew@lunn.ch>, <nex.sw.ncis.osdt.itp.upstreaming@intel.com>,
 <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH RFC net-next 7/7] netdev_features: convert
 NETIF_F_FCOE_MTU to IFF_FCOE_MTU
Message-ID: <20240411074709.249b3482@kernel.org>
In-Reply-To: <1f14cb75-ee6b-4a7d-9041-23a8cfcd8476@intel.com>
References: <20240405133731.1010128-1-aleksander.lobakin@intel.com>
	<20240405133731.1010128-8-aleksander.lobakin@intel.com>
	<20240408193806.18e227c8@kernel.org>
	<1f14cb75-ee6b-4a7d-9041-23a8cfcd8476@intel.com>
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On Thu, 11 Apr 2024 12:28:08 +0200 Alexander Lobakin wrote:
> > Any reason not to make it a bitfield? I haven't looked at the longer
> > patches but this one seems to be used like a basic bool.  
> 
> This whole enum could be made as bitfields, should we convert it? Would
> be a big patch tho ._.

As always, I haven't investigated closely :) But my thinking was -
we are at 34 bits in priv. We just need to convert 2 of them to
a bitfield, pick two with fewest uses. Then we can downgrade 
the field to u32 from ulonglong, and we can carry on adding bitfields?

> > But this definitely _is_ a uAPI change, right?  
> 
> Why?

It will be user visible, ethtool -k is losing a field.
Whether that's actually going to break anything depends on how silly
user space is.

As Andrew pointed out, definitely something that should be called out
in the commit message.