Subject: Re: [PATCH net-next] net: phy: lan87xx: fix access to wrong register of LAN87xx

From: Måns Rullgård <[email-masked]>
Date: Mon, 29 Mar 2021 12:19:15 +0100

Andre Edich <[email-masked]> writes:

> The function lan87xx_config_aneg_ext was introduced to configure
> LAN95xxA but as well writes to undocumented register of LAN87xx.
> This fix prevents that access.
>
> The function lan87xx_config_aneg_ext gets more suitable for the new
> behavior name.
>
> Reported-by: Måns Rullgård <[email-masked]>
> Fixes: 05b35e7eb9a1 ("smsc95xx: add phylib support")
> Signed-off-by: Andre Edich <[email-masked]>
> ---
>  drivers/net/phy/smsc.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/phy/smsc.c b/drivers/net/phy/smsc.c
> index ddb78fb4d6dc..d8cac02a79b9 100644
> --- a/drivers/net/phy/smsc.c
> +++ b/drivers/net/phy/smsc.c
> @@ -185,10 +185,13 @@ static int lan87xx_config_aneg(struct phy_device *phydev)
>  	return genphy_config_aneg(phydev);
>  }
>
> -static int lan87xx_config_aneg_ext(struct phy_device *phydev)
> +static int lan95xx_config_aneg_ext(struct phy_device *phydev)
>  {
>  	int rc;
>
> +	if (phydev->phy_id != 0x0007c0f0) /* not (LAN9500A or LAN9505A) */
> +		return lan87xx_config_aneg(phydev);
> +
>  	/* Extend Manual AutoMDIX timer */
>  	rc = phy_read(phydev, PHY_EDPD_CONFIG);
>  	if (rc < 0)
> @@ -441,7 +444,7 @@ static struct phy_driver smsc_phy_driver[] = {
>  	.read_status	= lan87xx_read_status,
>  	.config_init	= smsc_phy_config_init,
>  	.soft_reset	= smsc_phy_reset,
> -	.config_aneg	= lan87xx_config_aneg_ext,
> +	.config_aneg	= lan95xx_config_aneg_ext,
>
>  	/* IRQ related */
>  	.config_intr	= smsc_phy_config_intr,
> -- 

This seems to differentiate based on the "revision" field of the ID
register.  Can we be certain that a future update of chip won't break
this assumption?

-- 
Måns Rullgård