Subject: Re: [PATCH v4 net-next 04/10] net/ncsi: Ethtool operation to get NCSI topology

From: Andrew Lunn <[email-masked]>
Date: Thu, 4 May 2017 02:49:33 +0200

> +void ncsi_ethtool_register_dev(struct net_device *dev)
> +{
> +	struct ethtool_ops *ops;
> +
> +	ops = (struct ethtool_ops *)(dev->ethtool_ops);

Why do you need the cast here?

Ah, is it because net_device has:

          const struct ethtool_ops *ethtool_ops;

i.e. you are casting off the const.

> +	if (!ops)
> +		return;
> +
> +	ops->get_ncsi_channels = ncsi_get_channels;

and here you modify it. Which is going to blow up, because it will be
in a read only segment and should throw an opps when you write to it?

You need to export ncsi_get_channels, and let the underlying driver
add it to its own ethtool_ops.

   Andrew