netdev - Re: Fixed PHY Device Tree usage?

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Message-ID: <20130713190206.2a617983@skate>
Date:	Sat, 13 Jul 2013 19:02:06 +0200
From:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Florian Fainelli <florian@...nwrt.org>,
	netdev <netdev@...r.kernel.org>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Gregory Clément 
	<gregory.clement@...e-electrons.com>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Lior Amsalem <alior@...vell.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	Andy Fleming <afleming@...escale.com>
Subject: Re: Fixed PHY Device Tree usage?

Dear Grant Likely,

On Fri, 12 Jul 2013 23:44:21 +0100, Grant Likely wrote:

> I think this discussion is going in the wrong direction. The concept
> of a dummy phy is really a Linux kernel internal detail. Creating some
> kind of dummy MDIO bus node does not describe the hardware.

This is exactly what I was suggesting in my original e-mail of this
thread, see http://marc.info/?l=linux-netdev&m=137338762627063&w=2 :

"""
One option is to implement a Device Tree binding for the fixed PHY
driver (the exact DT binding would have to be discussed), but I'm
wondering whether describing a fixed PHY in the DT is actually correct,
because describing a fixed PHy is not really describing the hardware,
the hardware is actually a switch.
"""

> There is
> already support in the kernel for Ethernet MACs connected directly to
> a switch or other device. It is far better to describe how the MAC
> needs to be configured than to invent a non-existent phy. Search for
> "fixed-link" in the kernel tree to see how it is used.

As Florian pointed out, the of_phy_connect_fixed_link() comment
indicates:

 * This function is a temporary stop-gap and will be removed soon.  It is
 * only to support the fs_enet, ucc_geth and gianfar Ethernet drivers. Do
 * not call this function from new drivers.

Also, it would probably be good to have a few more helpers to make
parsing the "phy" and "fixed-link" property easier for network drivers.

Thanks for your feedback,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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