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Date:   Wed, 27 Oct 2021 16:46:32 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Yuiko.Oshino@microchip.com
Cc:     davem@davemloft.net, netdev@vger.kernel.org,
        Nisar.Sayed@microchip.com, UNGLinuxDriver@microchip.com
Subject: Re: [PATCH net-next] net: phy: microchip_t1: add cable test support
 for lan87xx phy
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References: <20211022183632.8415-1-yuiko.oshino@microchip.com>
 <YXMXeuMUVvmR5Zrc@lunn.ch>
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> >> +     /* start cable diag */
> >> +     /* check if part is alive - if not, return diagnostic error */
> >> +     rc = access_ereg(phydev, PHYACC_ATTR_MODE_READ,
> >PHYACC_ATTR_BANK_SMI,
> >> +                      0x00, 0);
> >> +     if (rc < 0)
> >> +             return rc;
> >> +
> >> +     if (rc != 0x2100)
> >> +             return -ENODEV;
> >
> >What does this actually mean? Would -EOPNOTSUPP be better?
> 
> This register should return the value of 0x2100. So if the return value is different, then I assume there is no device.

If the device does not exist, can we have go this far? Would probe of
the PHY failed? Or are you talking about a device within a device? Is
cable test implemented using an optional component?

      Andrew