linux-kernel - Re: [PATCH net v1 1/1] ethtool: netlink: do not return SQI value if link is down

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Message-ID: <dbfa3bc1-fff0-4dc7-a9f2-6cd304d4eaf8@lunn.ch>
Date: Thu, 4 Jul 2024 16:01:31 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Michal Kubecek <mkubecek@...e.cz>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Arun Ramadoss <arun.ramadoss@...rochip.com>,
	Woojung.Huh@...rochip.com, kernel@...gutronix.de,
	netdev@...r.kernel.org, UNGLinuxDriver@...rochip.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v1 1/1] ethtool: netlink: do not return SQI value if
 link is down

On Thu, Jul 04, 2024 at 07:40:07AM +0200, Oleksij Rempel wrote:
> Do not attach SQI value if link is down. "SQI values are only valid if link-up
> condition is present" per OpenAlliance specification of 100Base-T1
> Interoperability Test suite [1]. The same rule would apply for other link
> types.
> 
> [1] https://opensig.org/automotive-ethernet-specifications/#
> 
> Fixes: 8066021915924 ("ethtool: provide UAPI for PHY Signal Quality Index (SQI)")
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---
>  net/ethtool/linkstate.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/net/ethtool/linkstate.c b/net/ethtool/linkstate.c
> index b2de2108b356a..370ae628b13a4 100644
> --- a/net/ethtool/linkstate.c
> +++ b/net/ethtool/linkstate.c
> @@ -37,6 +37,8 @@ static int linkstate_get_sqi(struct net_device *dev)
>  	mutex_lock(&phydev->lock);
>  	if (!phydev->drv || !phydev->drv->get_sqi)
>  		ret = -EOPNOTSUPP;
> +	else if (!phydev->link)
> +		ret = -ENETDOWN;
>  	else
>  		ret = phydev->drv->get_sqi(phydev);
>  	mutex_unlock(&phydev->lock);
> @@ -55,6 +57,8 @@ static int linkstate_get_sqi_max(struct net_device *dev)
>  	mutex_lock(&phydev->lock);
>  	if (!phydev->drv || !phydev->drv->get_sqi_max)
>  		ret = -EOPNOTSUPP;
> +	else if (!phydev->link)
> +		ret = -ENETDOWN;
>  	else
>  		ret = phydev->drv->get_sqi_max(phydev);
>  	mutex_unlock(&phydev->lock);

I guess this part is optional. I think i've always seen hard coded
values. But this is O.K.

> @@ -93,12 +97,12 @@ static int linkstate_prepare_data(const struct ethnl_req_info *req_base,
>  	data->link = __ethtool_get_link(dev);
>  
>  	ret = linkstate_get_sqi(dev);
> -	if (ret < 0 && ret != -EOPNOTSUPP)
> +	if (ret < 0 && ret != -EOPNOTSUPP && ret != -ENETDOWN)
>  		goto out;
>  	data->sqi = ret;

So data->sqi becomes -ENETDOWN 


> -	if (data->sqi != -EOPNOTSUPP &&
> +	if (data->sqi != -EOPNOTSUPP && data->sqi != -ENETDOWN &&
>  	    nla_put_u32(skb, ETHTOOL_A_LINKSTATE_SQI, data->sqi))
>  		return -EMSGSIZE;

Thinking about the old code, if the driver returned something other
than -EOPNOTSUPP, it looks like the error code would make it to user
space. Is ethtool/iproute2 setup to correctly handle this? If it is,
maybe pass the -ENETDOWN to user space?

	Andrew