From: Tim Menninger <tmenninger@purestorage.com>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>,
netdev-maintainers <edumazet@google.com>,
kuba@kernel.org, pabeni@redhat.com, davem@davemloft.net,
netdev <netdev@vger.kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH net v1] net: dsa: mv88e6xxx: Make unsupported C45 reads return 0xffff
Date: Wed, 24 Jan 2024 07:59:48 -0800 [thread overview]
Message-ID: <CAO-L_47Cvh2QFiQ-Ug3Zsa4BnoC85MTN3W4cWJaJddtVUvmOPg@mail.gmail.com> (raw)
In-Reply-To: <32d96dd3-7fbb-49e5-8b05-269eac1ac80d@lunn.ch>
On Tue, Jan 23, 2024 at 2:59 PM Andrew Lunn <andrew@lunn.ch> wrote:
>
> > Does that mean if there's a device there but it doesn't support C45 (no
> > phy_read_c45), it will now return ENODEV?
>
> Yes, mv88e6xxx_mdio_read_c45() will return -ENODEV if
> chip->info->ops->phy_read_c45 is NULL. That will cause the scan of
> that address to immediately skip to the next address. This is old
> behaviour for C22:
>
> commit 02a6efcab675fe32815d824837784c3f42a7d892
> Author: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Date: Tue Apr 24 18:09:04 2018 +0200
>
> net: phy: allow scanning busses with missing phys
>
> Some MDIO busses will error out when trying to read a phy address with no
> phy present at that address. In that case, probing the bus will fail
> because __mdiobus_register() is scanning the bus for all possible phys
> addresses.
>
> In case MII_PHYSID1 returns -EIO or -ENODEV, consider there is no phy at
> this address and set the phy ID to 0xffffffff which is then properly
> handled in get_phy_device().
>
> And there are a few MDIO bus drivers which make use of this, e.g.
>
> static int lan9303_phy_read(struct dsa_switch *ds, int phy, int regnum)
> {
> struct lan9303 *chip = ds->priv;
> int phy_base = chip->phy_addr_base;
>
> if (phy == phy_base)
> return lan9303_virt_phy_reg_read(chip, regnum);
> if (phy > phy_base + 2)
> return -ENODEV;
>
> return chip->ops->phy_read(chip, phy, regnum);
>
> This Ethernet switch supports only a number of PHY addresses, and
> returns -ENODEV for the rest.
>
> So its a legitimate way to say there is nothing here.
>
> You suggestion of allowing ENOPSUPP for C45 would of fixed the
> problem, but C22 and C45 would support different error codes, which i
> don't like. Its better to be uniform.
>
> Andrew
Excellent, color me convinced.
prev parent reply other threads:[~2024-01-24 16:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-20 19:21 [PATCH net v1] net: dsa: mv88e6xxx: Make unsupported C45 reads return 0xffff Andrew Lunn
2024-01-22 12:24 ` Vladimir Oltean
2024-01-22 12:29 ` Vladimir Oltean
2024-01-22 12:52 ` Vladimir Oltean
2024-01-22 13:39 ` Andrew Lunn
2024-01-22 20:44 ` Tim Menninger
2024-01-22 23:01 ` Andrew Lunn
2024-01-23 15:27 ` Tim Menninger
2024-01-23 22:59 ` Andrew Lunn
2024-01-24 15:59 ` Tim Menninger [this message]
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