Subject: Re: [PATCH 1/4 v2] powerpc: document max-speed and interface-type properties

From: Segher Boessenkool <[email-masked]>
Date: Wed, 18 Apr 2007 01:18:24 +0200

>> "compatible" means "what kind of device is this", for the
>> purposes of a client program (i.e., Linux) matching a
>> driver to it (i.e., it should say what kind of PHY it
>> is, and phylib should use that info -- in most cases,
>> it won't need more than the least specific entry in
>> "compatible", i.e. "rgmii" or whatever.
>>
>
> sorry, I disagree; for me, a compatible entry in the PHY node would 
> look
> something like "marvell"

which would be completely wrong

> or "m88e11x1".

It should be something like "m88e11x1\0m88e1xxx\0rgmii" instead.
A "compatible" property can contain many values, ordered from
most exact to least exact.

> "rgmii" might indeed be
> something that PHY supports, but it tells the driver nothing about how
> to enable it (whereas "m88e11x1" would).  The rgmii designation in
> question in this thread is not a property of the PHY, but of the board.

It certainly is a property of the PHY as well.

>> So those UCCs should have a different "compatible" entry.
>> It's not rocket science.
>
> It's referring to the name of the driver,

No, not at all.  No device tree entry name/value has any
direct correspondence with Linux device driver names
(in principle; things can "accidentally" have the same
name, of course).

>> max-speed of connection = min(max-speed of enet, max-speed
>> of PHY) -- and both of those are implied by their respective
>> "compatible" properties.
>>
>
> Again, max-speed is exclusively for configuring the UCC itself,
> regardless of the connection speed.

If that is really true, and the value of that property
has nothing to do with the MAC<->PHY data channel, it should
have a different (not that generic) name.

Segher