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From: Andrew Lunn <andrew@lunn.ch>
To: Saravana Kannan <saravanak@google.com>
Cc: Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	kernel-team@android.com, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH v1 2/2] of: property: fw_devlink: Add support for "phy-handle" property
Date: Sat, 14 Aug 2021 17:22:53 +0200	[thread overview]
Message-ID: <YRffzVgP2eBw7HRz@lunn.ch> (raw)
In-Reply-To: <20210814023132.2729731-3-saravanak@google.com>

Hi Saravana

> Hi Andrew,
> 

> Also there
> are so many phy related properties that my head is spinning. Is there a
> "phy" property (which is different from "phys") that treated exactly as
> "phy-handle"?

Sorry, i don't understand your question.

> +	/*
> +	 * Device tree nodes pointed to by phy-handle never have struct devices
> +	 * created for them even if they have a "compatible" property. So
> +	 * return the parent node pointer.
> +	 */

We have a classic bus with devices on it. The bus master is registers
with linux using one of the mdiobus_register() calls. That then
enumerates the bus, looking at the 32 possible address on the bus,
using mdiobus_scan. It then gets a little complex, due to
history.

Originally, the only thing you could have on an MDIO bus was a
PHY. But devices on MDIO busses are more generic, and Linux gained
support for Ethernet switches on an MDIO bus, and there are a few
other sort device. So to keep the PHY API untouched, but to add these
extra devices, we added the generic struct mdio_device which
represents any sort of device on an MDIO bus. This has a struct device
embedded in it.

When we scan the bus and find a PHY, a struct phy_device is created,
which has an embedded struct mdio_device. The struct device in that is
then registered with the driver core.

So a phy-handle does point to a device, but you need to do an object
orientated style look at the base class to find it.

	   Andrew

  reply	other threads:[~2021-08-14 15:23 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-14  2:31 [PATCH v1 0/2] of: property: Support for few more properties Saravana Kannan
2021-08-14  2:31 ` [PATCH v1 1/2] of: property: fw_devlink: Add support for "leds" and "backlight" Saravana Kannan
2021-08-17 22:02   ` Rob Herring
2021-08-14  2:31 ` [PATCH v1 2/2] of: property: fw_devlink: Add support for "phy-handle" property Saravana Kannan
2021-08-14 15:22   ` Andrew Lunn [this message]
2021-08-16 20:43     ` Saravana Kannan
2021-08-16 21:11       ` Rob Herring
2021-08-17 18:18         ` Saravana Kannan
2021-08-16 21:15       ` Andrew Lunn
2021-08-18  2:13         ` Saravana Kannan

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