From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sascha Hauer Subject: Re: [RFC PATCHv2 3/4] of: provide a binding for fixed link PHYs Date: Thu, 19 Sep 2013 08:36:52 +0200 Message-ID: <20130919063652.GQ30088@pengutronix.de> References: <1378480701-12908-1-git-send-email-thomas.petazzoni@free-electrons.com> <1378480701-12908-4-git-send-email-thomas.petazzoni@free-electrons.com> <20130918042923.5D845C42CF7@trevor.secretlab.ca> <20130918150031.D9034C42CDF@trevor.secretlab.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20130918150031.D9034C42CDF-WNowdnHR2B42iJbIjFUEsiwD8/FfD2ys@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Grant Likely Cc: Florian Fainelli , Thomas Petazzoni , "David S. Miller" , netdev , "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Lior Amsalem , Mark Rutland , Christian Gmeiner , Ezequiel Garcia , Gregory Clement , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: devicetree@vger.kernel.org On Wed, Sep 18, 2013 at 10:00:31AM -0500, Grant Likely wrote: > On Wed, 18 Sep 2013 10:21:11 +0100, Florian Fainelli wrote: > > > > > > 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 -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html