linux-kernel - Re: [PATCH net] net/mlx5: report duplex full when speed is known

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Message-ID: <9c685b29-ccb9-4b40-94bc-819c5871dac8@lunn.ch>
Date: Sun, 14 Sep 2025 05:25:49 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Li Tian <litian@...hat.com>
Cc: netdev@...r.kernel.org, linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org, Saeed Mahameed <saeedm@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>, Mark Bloch <mbloch@...dia.com>,
	Leon Romanovsky <leon@...nel.org>, linux-rdma@...r.kernel.org,
	Haiyang Zhang <haiyangz@...rosoft.com>
Subject: Re: [PATCH net] net/mlx5: report duplex full when speed is known

On Sun, Sep 14, 2025 at 10:22:35AM +0800, Li Tian wrote:
> On Sat, Sep 13, 2025 at 10:12 PM Andrew Lunn <andrew@...n.ch> wrote:
> 
> > I'm confused with your commit message. You say DUPLEX used to be
> > reported as Full if the speed is known. How does c268ca6087f55 change
> > this?
> 
> Because in some circumstances like Azure, mlx5e_port_ptys2speed (now
> mlx5_port_ptys2info) does not return a speed.

So it can have link up without a speed? Speed is returned unknown? But
Azure is virtual? So both speed and duplex are both meaningless? There
is no physical communication medium. So unknown is reasonable.

> It does not return half duplex at all. It would be unknown. I'm just
> saying that half duplex shouldn't exist in modern Mellanox 5.

And that is relevant because?

> > Also, what sort of problems do you see with duplex unknown?
> 
> There were reports of RHEL seeing duplex unknown in ethtool
> on Azure Mellanox 5. The intention is to fix this.

Just reports of ethtool returning unknown? But nothing actually
broken?

	Andrew