netdev - Re: [PATCH 2/5] net: phy: hook up clause 45 autonegotiation restart

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Message-ID: <20170602124339.GO22219@n2100.armlinux.org.uk>
Date:   Fri, 2 Jun 2017 13:43:39 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org
Subject: Re: [PATCH 2/5] net: phy: hook up clause 45 autonegotiation restart

On Thu, Jun 01, 2017 at 10:16:17AM -0700, Florian Fainelli wrote:
> On 06/01/2017 09:24 AM, Russell King - ARM Linux wrote:
> > Checking 802.3-2015, in "22.2.4 Management functions", the first
> > sentence requires all PHYs that respond to Clause 22 cycles to
> > implement BMCR and BMSR.  However, my statement about unimplemented
> > registers returning zero seems to be a C45 thing, not a C22 thing,
> > according to the C22 PICS and "45.2 MDIO Interface Registers"
> > 
> > However, digging a bit further, "22.2.4.2.10 Auto-Negotiation complete"
> > states that bit 5 shall be zero if aneg has not completed or if aneg is
> > unimplemented.
> > 
> 
> So how about we are more defensive than that and if we are presented
> with a C45 PHY driver that does not have an aneg_done() function pointer
> set we return an error/warning during driver registration?

We don't mark drivers as being C22 or C45, we rely on them matching
the IDs and/or the probe function making that decision, so it's a
tad difficult to make that decision at driver registration time.

We could reject an attempt to probe a C45 phy with a driver that
does not provide an aneg_done() pointer.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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