netdev - RE: [PATCH net-next V3 5/8] net/mlx4_en: Adding support of turning off link autonegotiation via ethtool

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB0273B7E@AcuExch.aculab.com>
Date:   Mon, 30 Jan 2017 14:00:28 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Tariq Toukan' <tariqt@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Ariel Levkovich <lariel@...lanox.com>
Subject: RE: [PATCH net-next V3 5/8] net/mlx4_en: Adding support of turning
 off link autonegotiation via ethtool

From: Tariq Toukan
> Sent: 29 January 2017 16:56
> From: Ariel Levkovich <lariel@...lanox.com>
> 
> This feature will allow the user to disable auto negotiation
> on the port for mlx4 devices while setting the speed is limited
> to 1GbE speeds.
> Other speeds will not be accepted in autoneg off mode.

What is the rationale behind this change?

When I was writing ethernet drivers it was always better to
leave autonegotiation enabled with restricted modes than to
fix the speed.

That ensures that far end is using the same mode.

This was particularly important for FDX v HDX at 10/100 speeds,
but I suspect it is equally relevant now.

	David