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Date: Sat, 6 Apr 2024 17:51:07 +0200
From: Andrew Lunn <andrew@lunn.ch>
To: Maxime Chevallier <maxime.chevallier@bootlin.com>
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Subject: Re: [PATCH net-next v11 01/13] net: phy: Introduce ethernet link
 topology representation
Message-ID: <f0a33859-bdb7-474d-8c23-edb158b0fd91@lunn.ch>
References: <20240404093004.2552221-1-maxime.chevallier@bootlin.com>
 <20240404093004.2552221-2-maxime.chevallier@bootlin.com>
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In-Reply-To: <20240404093004.2552221-2-maxime.chevallier@bootlin.com>

On Thu, Apr 04, 2024 at 11:29:51AM +0200, Maxime Chevallier wrote:
> Link topologies containing multiple network PHYs attached to the same
> net_device can be found when using a PHY as a media converter for use
> with an SFP connector, on which an SFP transceiver containing a PHY can
> be used.
> 
> With the current model, the transceiver's PHY can't be used for
> operations such as cable testing, timestamping, macsec offload, etc.
> 
> The reason being that most of the logic for these configuration, coming
> from either ethtool netlink or ioctls tend to use netdev->phydev, which
> in multi-phy systems will reference the PHY closest to the MAC.
> 
> Introduce a numbering scheme allowing to enumerate PHY devices that
> belong to any netdev, which can in turn allow userspace to take more
> precise decisions with regard to each PHY's configuration.
> 
> The numbering is maintained per-netdev, in a phy_device_list.
> The numbering works similarly to a netdevice's ifindex, with
> identifiers that are only recycled once INT_MAX has been reached.
> 
> This prevents races that could occur between PHY listing and SFP
> transceiver removal/insertion.
> 
> The identifiers are assigned at phy_attach time, as the numbering
> depends on the netdevice the phy is attached to. The PHY index can be
> re-used for PHYs that are persistent.
> 
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>

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

    Andrew