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

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.  This practically (and I've tested it) means that
genphy_aneg_done() never indicates negotiation completion, and the
link never comes up.

Seems like a trap waiting for somebody to fall into it. The additional
code might be worth it to avoid placing this trap.

The "trap" means a non-functional driver, since the link doesn't
come up.

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