Subject: Re: [PATCH v1 1/3] net/ethtool/ioctl: return -EOPNOTSUPP if we have no phy stats

From: Andrew Lunn <[email-masked]>
Date: Fri, 25 Nov 2022 20:02:50 +0100

On Fri, Nov 25, 2022 at 07:49:11PM +0300, Daniil Tatianin wrote:
> It's not very useful to copy back an empty ethtool_stats struct and
> return 0 if we didn't actually have any stats. This also allows for
> further simplification of this function in the future commits.
> 
> Signed-off-by: Daniil Tatianin <[email-masked]>
> ---
>  net/ethtool/ioctl.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
> index 57e7238a4136..071e9bf16007 100644
> --- a/net/ethtool/ioctl.c
> +++ b/net/ethtool/ioctl.c
> @@ -2089,11 +2089,15 @@ static int ethtool_get_phy_stats(struct net_device *dev, void __user *useraddr)
>  		n_stats = phy_ops->get_sset_count(phydev);
>  	else
>  		n_stats = ops->get_sset_count(dev, ETH_SS_PHY_STATS);
> +
>  	if (n_stats < 0)

Please don't make unneeded white space changes. It just distracts from
the real change being made here.

>  		return n_stats;
>  	if (n_stats > S32_MAX / sizeof(u64))
>  		return -ENOMEM;
> -	WARN_ON_ONCE(!n_stats);
> +	if (!n_stats) {
> +		WARN_ON_ONCE(1);
> +		return -EOPNOTSUPP;
> +	}

WARN_ON_ONCE() returns the result of the comparison being made. so you can do:

	if (WARN_ON_ONCE(!n_stats))
		return -EOPNOTSUPP;

	Andrew