Re: [PATCH net v3 1/2] net: ravb: handle unavailable PTP clock

[Vadim Fedorenko <vadim.fedorenko@linux.dev>]

On 06/08/2026 10:51, xuanqiang.luo@linux.dev wrote:
> From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
> 
> The PTP clock is registered by ravb_open(), not ravb_probe(). Therefore,
> priv->ptp.clock is NULL between register_netdev() and the first open, and
> ethtool -T triggers a NULL dereference in ptp_clock_index().
> 
> ptp_clock_register() may also return an error pointer, which can reach
> ptp_clock_index() or ptp_clock_unregister().
> 
> Normalize registration errors to NULL and only query or unregister the
> clock when it is present. Leave phc_index at -1 when no PHC is registered,
> while preserving the static hardware timestamping capabilities.
> 
> Fixes: a0d2f20650e8 ("Renesas Ethernet AVB PTP clock driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
> ---
>   drivers/net/ethernet/renesas/ravb_main.c |  3 ++-
>   drivers/net/ethernet/renesas/ravb_ptp.c  | 12 ++++++++++--
>   2 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 5f88733094d0f..3a9d9f8718216 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -1779,7 +1779,8 @@ static int ravb_get_ts_info(struct net_device *ndev,
>   			(1 << HWTSTAMP_FILTER_NONE) |
>   			(1 << HWTSTAMP_FILTER_PTP_V2_L2_EVENT) |
>   			(1 << HWTSTAMP_FILTER_ALL);
> -		info->phc_index = ptp_clock_index(priv->ptp.clock);
> +		if (priv->ptp.clock)
> +			info->phc_index = ptp_clock_index(priv->ptp.clock);
>   	}
>   
>   	return 0;
> diff --git a/drivers/net/ethernet/renesas/ravb_ptp.c b/drivers/net/ethernet/renesas/ravb_ptp.c
> index 226c6c0ab945b..eaf07cb8eadfa 100644
> --- a/drivers/net/ethernet/renesas/ravb_ptp.c
> +++ b/drivers/net/ethernet/renesas/ravb_ptp.c
> @@ -315,6 +315,7 @@ void ravb_ptp_interrupt(struct net_device *ndev)
>   void ravb_ptp_init(struct net_device *ndev, struct platform_device *pdev)
>   {
>   	struct ravb_private *priv = netdev_priv(ndev);
> +	struct ptp_clock *clock;
>   	unsigned long flags;
>   
>   	priv->ptp.info = ravb_ptp_info;
> @@ -327,7 +328,13 @@ void ravb_ptp_init(struct net_device *ndev, struct platform_device *pdev)
>   	ravb_modify(ndev, GCCR, GCCR_TCSS, GCCR_TCSS_ADJGPTP);
>   	spin_unlock_irqrestore(&priv->lock, flags);
>   
> -	priv->ptp.clock = ptp_clock_register(&priv->ptp.info, &pdev->dev);
> +	clock = ptp_clock_register(&priv->ptp.info, &pdev->dev);
> +	if (IS_ERR(clock)) {
> +		netdev_err(ndev, "failed to register PTP clock: %pe\n", clock);
> +		clock = NULL;
> +	}
> +
> +	priv->ptp.clock = clock;
>   }
>   
>   void ravb_ptp_stop(struct net_device *ndev)
> @@ -337,5 +344,6 @@ void ravb_ptp_stop(struct net_device *ndev)
>   	ravb_write(ndev, 0, GIC);
>   	ravb_write(ndev, 0, GIS);
>   
> -	ptp_clock_unregister(priv->ptp.clock);
> +	if (priv->ptp.clock)
> +		ptp_clock_unregister(priv->ptp.clock);
>   }

Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>