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Date:   Thu, 16 Jan 2020 21:47:11 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>, davem@...emloft.net,
        linux@...linux.org.uk, andrew@...n.ch, f.fainelli@...il.com
Cc:     netdev@...r.kernel.org,
        Alex Marginean <alexandru.marginean@....com>
Subject: Re: [PATCH net-next] net: phy: don't crash in phy_read/_write_mmd
 without a PHY driver

On 16.01.2020 18:46, Vladimir Oltean wrote:
> From: Alex Marginean <alexandru.marginean@....com>
> 
> The APIs can be used by Ethernet drivers without actually loading a PHY
> driver. This may become more widespread in the future with 802.3z
> compatible MAC PCS devices being locally driven by the MAC driver when
> configuring for a PHY mode with in-band negotiation.
> 
> Check that drv is not NULL before reading from it.
> 
If there's no dedicated PHY driver, then the genphy driver is bound.
I think therefore we don't face issues with the current code.
But the change looks reasonable.

> Signed-off-by: Alex Marginean <alexandru.marginean@....com>
> ---
> If this hasn't been reported by now I assume it wasn't an issue so far.
> So I've targeted the patch for net-next and not provided a Fixes: tag.
> 
>  drivers/net/phy/phy-core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
> index 769a076514b0..a4d2d59fceca 100644
> --- a/drivers/net/phy/phy-core.c
> +++ b/drivers/net/phy/phy-core.c
> @@ -387,7 +387,7 @@ int __phy_read_mmd(struct phy_device *phydev, int devad, u32 regnum)
>  	if (regnum > (u16)~0 || devad > 32)
>  		return -EINVAL;
>  
> -	if (phydev->drv->read_mmd) {
> +	if (phydev->drv && phydev->drv->read_mmd) {
>  		val = phydev->drv->read_mmd(phydev, devad, regnum);
>  	} else if (phydev->is_c45) {
>  		u32 addr = MII_ADDR_C45 | (devad << 16) | (regnum & 0xffff);
> @@ -444,7 +444,7 @@ int __phy_write_mmd(struct phy_device *phydev, int devad, u32 regnum, u16 val)
>  	if (regnum > (u16)~0 || devad > 32)
>  		return -EINVAL;
>  
> -	if (phydev->drv->write_mmd) {
> +	if (phydev->drv && phydev->drv->write_mmd) {
>  		ret = phydev->drv->write_mmd(phydev, devad, regnum, val);
>  	} else if (phydev->is_c45) {
>  		u32 addr = MII_ADDR_C45 | (devad << 16) | (regnum & 0xffff);
> 

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