netdev - Re: [PATCH net-next v5 2/5] ethtool: netlink: add ETHTOOL_MSG_MSE

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Message-ID: <20250915080720.17646515@kernel.org>
Date: Mon, 15 Sep 2025 08:07:20 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Andrew Lunn <andrew@...n.ch>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon
 Horman <horms@...nel.org>, Donald Hunter <donald.hunter@...il.com>,
 Jonathan Corbet <corbet@....net>, Heiner Kallweit <hkallweit1@...il.com>,
 Russell King <linux@...linux.org.uk>, Kory Maincent
 <kory.maincent@...tlin.com>, Maxime Chevallier
 <maxime.chevallier@...tlin.com>, Nishanth Menon <nm@...com>,
 kernel@...gutronix.de, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, UNGLinuxDriver@...rochip.com,
 linux-doc@...r.kernel.org, Michal Kubecek <mkubecek@...e.cz>, Roan van Dijk
 <roan@...tonic.nl>
Subject: Re: [PATCH net-next v5 2/5] ethtool: netlink: add
 ETHTOOL_MSG_MSE_GET and wire up PHY MSE access

On Mon, 15 Sep 2025 11:30:52 +0200 Oleksij Rempel wrote:
> On Fri, Sep 12, 2025 at 05:00:53PM -0700, Jakub Kicinski wrote:
> > On Fri, 12 Sep 2025 12:07:42 +0200 Oleksij Rempel wrote:  
> > > I would prefer to keep u64 for refresh-rate-ps and num-symbols.
> > > 
> > > My reasoning comes from comparing the design decisions of today's industrial
> > > hardware to the projected needs of upcoming standards like 800 Gbit/s. This
> > > analysis shows that future PHYs will require values that exceed the limits of a
> > > u32.  
> > 
> > but u64 may or may not also have some alignment expectations, which uint
> > explicitly excludes  
> 
> just to confirm - if we declare an attribute as type: uint in the YAML
> spec, the kernel side can still use nla_put_u64() to send a 64-bit
> value, correct? My understanding is that uint is a flexible integer
> type, so userspace decoders will accept both 4-byte and 8-byte encodings
> transparently.

Theoretically, and yes. But why would you use put_u64 and not
put_uint() ?