linux-kernel - Re: [PATCH net v2] phy: mscc: Fix PTP for vsc8574 and VSC8572

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Message-ID: <aNZhB5LnqH5voBBR@shell.armlinux.org.uk>
Date: Fri, 26 Sep 2025 10:46:47 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc: Vladimir Oltean <vladimir.oltean@....com>,
	Jakub Kicinski <kuba@...nel.org>, andrew@...n.ch,
	hkallweit1@...il.com, davem@...emloft.net, edumazet@...gle.com,
	pabeni@...hat.com, richardcochran@...il.com,
	vadim.fedorenko@...ux.dev, christophe.jaillet@...adoo.fr,
	rosenp@...il.com, steen.hegelund@...rochip.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] phy: mscc: Fix PTP for vsc8574 and VSC8572

On Mon, Sep 22, 2025 at 02:33:01PM +0200, Horatiu Vultur wrote:
> Thanks for the advice.
> What about to make the PHY_ID_VSC8572 and PHY_ID_VSC8574 to use
> vsc8584_probe() and then in this function just have this check:
> 
> ---
> if ((phydev->phy_id & 0xfffffff0) != PHY_ID_VSC8572 &&
>     (phydev->phy_id & 0xfffffff0) != PHY_ID_VSC8574) {
> 	if ((phydev->phy_id & MSCC_DEV_REV_MASK) != VSC8584_REVB) {
> 		dev_err(&phydev->mdio.dev, "Only VSC8584 revB is supported.\n");
> 		return -ENOTSUPP;
> 	}
> }

Please, no, not like this. Have a look how the driver already compares
PHY IDs in the rest of the code.

When a PHY driver is matched, the PHY ID is compared using the
.phy_id and .phy_id_mask members of the phy_driver structure.

The .phy_id is normally stuff like PHY_ID_VSC8572 and PHY_ID_VSC8574.

When the driver is probed, phydev->drv is set to point at the
appropriate phy_driver structure. Thus, the tests can be simplified
to merely looking at phydev->drv->phy_id:

	if (phydev->drv->phy_id != PHY_ID_VSC8572 &&
	    phydev->drv->phy_id != PHY_ID_VSC8574 &&
	    (phydev->phy_id & MSCC_DEV_REV_MASK) != VSC8584_REVB) {
...

Alternatively, please look at the phy_id*() and phydev_id_compare()
families of functions.

-- 
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