Re: [PATCH net v2 1/2] net: ethtool: don't match a hwtstamp provider on a device without a PHC

[Nicolai Buchwitz <nb@tipi-net.de>]

+CC Maxime & Bjorn

On 23.9.2026 14:16, Nicolai Buchwitz wrote:
> A device without a PHC reports phc_index -1. A request for index
> 0xFFFFFFFF is stored in an int and becomes -1 too, so the two match and
> a netdev provider is selected on a device that has none.
> 
> Fix this and only match a real PHC index.
> 
> Fixes: b9e3f7dc9ed9 ("net: ethtool: tsinfo: Enhance tsinfo to support 
> several hwtstamp by net topology")
> Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
> ---
>  net/ethtool/common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/ethtool/common.c b/net/ethtool/common.c
> index 23db40618fed..23e8282563cc 100644
> --- a/net/ethtool/common.c
> +++ b/net/ethtool/common.c
> @@ -980,7 +980,7 @@ int ethtool_net_get_ts_info_by_phc(struct 
> net_device *dev,
>  	if (err)
>  		return err;
> 
> -	if (info->phc_index == hwprov_desc->index &&
> +	if (info->phc_index >= 0 && info->phc_index == hwprov_desc->index &&
>  	    net_support_hwtstamp_qualifier(dev, hwprov_desc->qualifier))
>  		return 0;