netdev - Re: [RFC PATCH V4 net-next 1/5] ethtool: Allow network drivers to dump arbitrary EEPROM data

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Date:   Tue, 23 Mar 2021 01:54:30 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Moshe Shemesh <moshe@...dia.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Adrian Pop <pop.adrian61@...il.com>,
        Michal Kubecek <mkubecek@...e.cz>,
        Don Bollinger <don@...bollingers.org>, netdev@...r.kernel.org,
        Vladyslav Tarasiuk <vladyslavt@...dia.com>
Subject: Re: [RFC PATCH V4 net-next 1/5] ethtool: Allow network drivers to
 dump arbitrary EEPROM data

> +static int eeprom_prepare_data(const struct ethnl_req_info *req_base,
> +			       struct ethnl_reply_data *reply_base,
> +			       struct genl_info *info)
> +{
> +	struct eeprom_reply_data *reply = MODULE_EEPROM_REPDATA(reply_base);
> +	struct eeprom_req_info *request = MODULE_EEPROM_REQINFO(req_base);
> +	struct ethtool_module_eeprom page_data = {0};
> +	struct net_device *dev = reply_base->dev;
> +	int ret;
> +
> +	if (!dev->ethtool_ops->get_module_eeprom_by_page)
> +		return -EOPNOTSUPP;
> +
> +	/* Allow dumps either of low or high page without crossing half page boundary */
> +	if ((request->offset < ETH_MODULE_EEPROM_PAGE_LEN / 2 &&
> +	     request->offset + request->length > ETH_MODULE_EEPROM_PAGE_LEN / 2) ||
> +	    request->offset + request->length > ETH_MODULE_EEPROM_PAGE_LEN)
> +		return -EINVAL;

Please keep all the parameter validation together, in
eeprom_parse_request(). At some point, we may extend
eeprom_parse_request() to make use of extack, to indicate which
parameter is invalid. Just getting an -EINVAL can be hard to debug,
where as NL_SET_ERR_MSG_ATTR() can help the user.

      Andrew