netdev - RE: SMSC 8720a/MDIO/PHY help.

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Date:	Fri, 15 Apr 2011 15:53:41 -0500
From:	ANDY KENNEDY <ANDY.KENNEDY@...ran.com>
To:	Andy Fleming <afleming@...il.com>
CC:	<michael@...sch.at>, <netdev@...r.kernel.org>
Subject: RE: SMSC 8720a/MDIO/PHY help.

> -----Original Message-----
> From: netdev-owner@...r.kernel.org [mailto:netdev-
> owner@...r.kernel.org] On Behalf Of Andy Fleming
> Sent: Friday, April 15, 2011 3:30 PM
> To: ANDY KENNEDY
> Cc: michael@...sch.at; netdev@...r.kernel.org
> Subject: Re: SMSC 8720a/MDIO/PHY help.
> 
> On Wed, Apr 13, 2011 at 4:38 PM, ANDY KENNEDY
> <ANDY.KENNEDY@...ran.com> wrote:
> >> -----Original Message-----
> >> From: Michael Riesch [mailto:michael@...sch.at]
> >> Sent: Wednesday, April 13, 2011 4:19 PM
> >> To: netdev@...r.kernel.org
> >> Cc: ANDY KENNEDY
> >> Subject: Re: SMSC 8720a/MDIO/PHY help.
> >>
> >>
> >> > If you have an idea of something for me to try, I'd love to
> >> entertain
> >> > it.
> >>
> >> I am rather new to PHYLIB, but these are my ideas:
> >>
> >>  1) make sure phy_connect is executed (AFIAK called by MDIO bus
> >> driver)
> >
> > Going through the phy.txt doc under Documentation/networking:
> > PHY Abstraction Layer
> > (Updated 2008-04-08)
> > though it may be a bit out-of-date, I did see what you are
> talking about.  What I'm hung up on at the moment is the behavior
> of adjust_link().  It appears that I only need to start the queues,
> though I don't know.
> >
> >>
> >>  2) maybe you need to call phy_start / phy_stop (AFAIK from the
> PHY
> >> driver's open / close function)
> >
> > Currently, when I do this I only get the call to adjust_link()
> over and over again.
> 
> 
> ...this means that the state machine is running.  The PHY is
> polling
> every couple seconds to report the current state. It calls
> adjust_link() to keep the net_device up-to-date on that state. What
> other behavior are you expecting to see?

Well, you see I was expecting it to be up and running at that point (to be able to assign an IP, pass traffic, etc) -- but that is due to ignorance of (1) network device drivers, (2) PHY device drivers, (3) MDIO bus drivers, (4) General level 2 networking, (5) ;) get the point?

See, I'm totally new to networking (at this level).  Device drivers, yes, but not networking.

Though, after Michael's e-mails, I have discovered that I have to
1) Make the MDIO bus work
2) Establish communications with the MDIO driver (in this case smsc.c under net/phy)
3) Make all my NDO required functions for controlling the "real" network device -- I was unaware that the PHY _WASN'T_ the network device.
4) Call phy_connect_direct (so I don't trash the already existent smsc.c as before stated)
5) Finally, after the NDO functions are written, register the NDO with the networking layer of the Kernel.

One thing I have done wrong (realized AFTER depending upon the work I've done) is that I should have split out the MDIO and the network device.  

Now, where is the document that explains all this.  The PHY document is very informative, however, if you don't know that a PHY is NOT a network device, you're kinda outta luck.  Even Wiki reports a PHY as the Physical Link layer of the OSI model.  Which, again, doesn't tell the ignorant much.

I have a bit more knowledge now, however, and I think I've about got my network device up (that would be I'm only 80% ignorant now ;).

Andy
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