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

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Message-ID: <20170601131955.GH9282@lunn.ch>
Date:   Thu, 1 Jun 2017 15:19:55 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH 2/5] net: phy: hook up clause 45 autonegotiation restart

On Thu, Jun 01, 2017 at 02:09:00PM +0100, Russell King - ARM Linux wrote:
> On Thu, Jun 01, 2017 at 03:05:27PM +0200, Andrew Lunn wrote:
> > So you are saying a 10G PHY driver always needs to have a aneg_done
> > callback, even if it just needs to call phygen_c45_aneg_done?
> > 
> > This seems a bit error prone. I can see somebody writing a 10G driver,
> > leaving out aneg_done() and having the c22 version called. Is the read
> > of MII_BMSR likely to return 0xffff, since the register does not
> > exist? If so, genphy_aneg_done() is likely to always return
> > BMSR_ANEGCOMPLETE.
> 
> Don't forget that the read will fail, so phy_read() will return a
> negative number.

By fail, you mean return something like -EIO or -ETIMEOUT? Is this
guaranteed in the code somewhere? This particular Marvell PHY only
does c45. But i could imagine some other PHYs answering a c22 request
with 0xffff.

     Andrew