netdev - Re: [PATCH net-next v3 3/3] phy: dp83td510: Utilize ALCD for cable length measurement when link is active

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <3b5f1f4e-d132-4f42-a516-29a0a827bf59@lunn.ch>
Date: Thu, 22 Aug 2024 17:50:30 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jonathan Corbet <corbet@....net>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH net-next v3 3/3] phy: dp83td510: Utilize ALCD for cable
 length measurement when link is active

On Thu, Aug 22, 2024 at 02:07:03PM +0200, Oleksij Rempel wrote:
> In industrial environments where 10BaseT1L PHYs are replacing existing
> field bus systems like CAN, it's often essential to retain the existing
> cable infrastructure. After installation, collecting metrics such as
> cable length is crucial for assessing the quality of the infrastructure.
> Traditionally, TDR (Time Domain Reflectometry) is used for this purpose.
> However, TDR requires interrupting the link, and if the link partner
> remains active, the TDR measurement will fail.
> 
> Unlike multi-pair systems, where TDR can be attempted during the MDI-X
> switching window, 10BaseT1L systems face greater challenges. The TDR
> sequence on 10BaseT1L is longer and coincides with uninterrupted
> autonegotiation pulses, making TDR impossible when the link partner is
> active.
> 
> The DP83TD510 PHY provides an alternative through ALCD (Active Link
> Cable Diagnostics), which allows for cable length measurement without
> disrupting an active link. Since a live link indicates no short or open
> cable states, ALCD can be used effectively to gather cable length
> information.
> 
> Enhance the dp83td510 driver by:
> - Leveraging ALCD to measure cable length when the link is active.
> - Bypassing TDR when a link is detected, as ALCD provides the required
>   information without disruption.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew