netdev - Re: [PATCH] DT: net: document Ethernet bindings in one place

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Date:	Tue, 21 Jan 2014 02:33:08 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Rob Herring <robherring2@...il.com>
CC:	netdev@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Rob Landley <rob@...dley.net>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH] DT: net: document Ethernet bindings in one place

On 01/21/2014 12:20 AM, Rob Herring wrote:

>>>> This patch is an attempt to gather the Ethernet related bindings in one
>>>> file,
>>>> like it's done in the MMC and some other subsystems. It should save the
>>>> trouble
>>>> of documenting several properties over and over in each binding document.

>>>> I have used the Embedded Power Architecture(TM) Platform Requirements
>>>> (ePAPR)
>>>> standard as a base for the properties description, also documenting some
>>>> ad-hoc
>>>> properties that have been introduced over time despite having direct
>>>> analogs in
>>>> ePAPR.

>>>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>

>>>> ---
>>>> The patch is against DaveM's 'net-next.git' repo and the DaVinci EMAC
>>>> bindings
>>>> fix I've posted yesterday:

>>>> http://patchwork.ozlabs.org/patch/311854/

>> [...]

>>>> Index: net-next/Documentation/devicetree/bindings/net/ethernet.txt
>>>> ===================================================================
>>>> --- /dev/null
>>>> +++ net-next/Documentation/devicetree/bindings/net/ethernet.txt
>>>> @@ -0,0 +1,20 @@
>>>> +The following properties are common to the Ethernet controllers:
>>>> +
>>>> +- local-mac-address: array of 6 bytes, specifies the MAC address that
>>>> was
>>>> +  assigned to the network device;
>>>> +- mac-address: array of 6 bytes, specifies the MAC address that was last
>>>> used by
>>>> +  the boot program; should be used in cases where the MAC address
>>>> assigned to
>>>> +  the device by the boot program is different from the
>>>> "local-mac-address"
>>>> +  property;
>>>> +- max-speed: number, specifies maximum speed in Mbit/s supported by the
>>>> device;
>>>> +- phy-mode: string, operation mode of the PHY interface; supported
>>>> values are
>>>> +  "mii", "gmii", "sgmii", "tbi", "rev-mii", "rmii", "rgmii", "rgmii-id",
>>>> +  "rgmii-rxid", "rgmii-txid", "rtbi", "smii", "xgmii";

>>> Mark this as deprecated

>>     That's kind of wishful thinking at this point, as that's what the
>> majority of drivers use. I'm unsure of the reasons why that was done,
>> probably people just didn't read the proper specs...

> Or the spec was defined after those bindings.

    No, that's not likely as "phy-connection-type" prop seems very old, most 
probably predating ePAPR. ePAPR exists since 2008, kernel support for 
"phy-mode" prop dates back only to 2011.

> Deprecating does not
> matter for existing bindings. It's only defining new ones that are
> affected. I was more concerned with giving people guidance on which
> one to use for new bindings.

    If "phy-connection-type" is to be used, it makes sense to modify 
of_get_phy_mode() to also look for that prop, right?

>>> in favor of phy-connection-type

>>     That one is only used by the oldish PowerPC 'gianfar' driver.

>>> so it's use does not spread.

>>     I'm afraid that's too late, it has spread very far, so that
>> of_get_phy_mode() handles that property, not "phy-connection-type".

> Uggg, I guess this is a case of a defacto standard then if the kernel
> doesn't even support it.

    What's your guess on what to do on these 2 props then? Still deprecate 
"phy-mode"?

>>>> +- phy-connection-type: the same as "phy-mode" property (but described in
>>>> ePAPR);
>>>> +- phy-handle: phandle, specifies a reference to a node representing a
>>>> PHY
>>>> +  device (this property is described in ePAPR);
>>>> +- phy: the same as "phy-handle" property (but actually ad-hoc one).

>>> Mark this as deprecated in favor of phy-handle.

>>     Here situation is more optimistic. Quite many drivers still use
>> "phy-handle", though some use even more exotic props I didn't document here.

> Perhaps flagging as "Not recommended for new bindings" would be nicer wording...

    Perhaps.

> Rob

WBR, Sergei

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