Re: [RFC PATCHv2 3/4] of: provide a binding for fixed link PHYs

On Wed, Sep 18, 2013 at 10:00:31AM -0500, Grant Likely wrote:

On Wed, 18 Sep 2013 10:21:11 +0100, Florian Fainelli [off-list ref] wrote:

quoted

quoted

I understand what you're trying to do here, but it causes a troublesome
leakage of implementation detail into the binding, making the whole
thing look very odd. This binding tries to make a fixed link look
exactly like a real PHY even to the point of including a phandle to the
phy. But having a phandle to a node which is *always* a direct child of
the MAC node is redundant and a rather looney. Yes, doing it that way
makes it easy for of_phy_find_device() to be transparent for fixed link,
but that should *not* drive bindings, especially when that makes the
binding really rather weird.

This is not exactly true in the sense that the "new" binding just
re-shuffles the properties representation into something that is
clearer and more extendible but there is not much difference in the
semantics.

That's not my point in the above paragraph. My point is a binding that
consists of a phandle to a node that is always a direct child is goofy
and wrong.

It's not necessarily a direct child. Most of these fixed links are really
ethernet switches. These are (mostly) i2c devices which are under their
corresponding i2c bus node. Using a phandle from the ethernet MAC to
the port of a switch not only provides the link information, but also the
information to which port of the switch the MAC is connected.

Another situation is that some SoCs have a MDIO bus external to the MAC
and possibly shared for multiple ethernet MACs. This also requires a
phandle from the MAC to the MDIO bus.

So we have the situation that we need a phandle from the MAC to something
that provides a link. For consistency it would be good to always use a
phandle instead of having an inflexible 'fixed-link' property.

You're right, the binding doesn't provide anything new, but I think it
straightens things up for the future.

Sascha


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