netdev - Re: net: macb: fail when there's no PHY

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Date:   Wed, 2 Dec 2020 19:35:31 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Grant Edwards <grant.b.edwards@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Subject: Re: net: macb: fail when there's no PHY

> When using the SIOC[SG]MIIREG ioctl() call, how does one control
> whether the fake fixed-link bus is accessed or the real macb-mdio bus
> is accessed?

As far as i remember, that ioctl is based on the interface name. So it
will access the MDIO bus of the PHY that is attached to the MAC.

I guess you have user space drivers using the IOCTL to access devices
on the real bus? A switch? Can you swap to a DSA driver?

> How does the macb driver decide which bus/id combination to use as
> "the phy" that controls the link duplex/speed settting the the MAC?

phy-handle points to a PHY.

	   Andrew