linux-kernel - Re: [PATCH net-next v2 2/4] net: phy: micrel: Introduce lanphy_modify_page

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Message-ID: <20250725064304.nrpzgaz6ur3zsidc@DEN-DL-M31836.microchip.com>
Date: Fri, 25 Jul 2025 08:43:04 +0200
From: Horatiu Vultur <horatiu.vultur@...rochip.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
CC: <andrew@...n.ch>, <hkallweit1@...il.com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<richardcochran@...il.com>, <o.rempel@...gutronix.de>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v2 2/4] net: phy: micrel: Introduce
 lanphy_modify_page_reg

The 07/24/2025 21:41, Russell King (Oracle) wrote:

Hi Russell,

> 
> On Thu, Jul 24, 2025 at 10:08:24PM +0200, Horatiu Vultur wrote:
> > +static int lanphy_modify_page_reg(struct phy_device *phydev, int page, u16 addr,
> > +                               u16 mask, u16 set)
> > +{
> > +     int new, ret;
> > +
> > +     ret = lanphy_read_page_reg(phydev, page, addr);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     new = (ret & ~mask) | set;
> > +     if (new == ret)
> > +             return 0;
> > +
> > +     ret = lanphy_write_page_reg(phydev, page, addr, new);
> 
> Please implement this more safely. Another user could jump in between
> the read and the write and change this same register.
> 
>         phy_lock_mdio_bus(phydev);
>         __phy_write(phydev, LAN_EXT_PAGE_ACCESS_CONTROL, page);
>         __phy_write(phydev, LAN_EXT_PAGE_ACCESS_ADDRESS_DATA, addr);
>         __phy_write(phydev, LAN_EXT_PAGE_ACCESS_CONTROL,
>                     (page | LAN_EXT_PAGE_ACCESS_CTRL_EP_FUNC));
>         ret = __phy_modify_changed(phydev, LAN_EXT_PAGE_ACCESS_ADDRESS_DATA,
>                                    mask, set);
>         if (ret < 0)
>                 phydev_err(phydev, "Error: phy_modify has returned error %d\n",
>                            ret);
> 
> unlock:
>         phy_unlock_mdio_bus(phydev);
> 
>         return ret;
> 
> is all that it'll take (assuming the control/address register doesn't
> need to be rewritten.)

Thanks, I will look into this.

> 
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!

-- 
/Horatiu