Subject: Re: [PATCH net-next v17 13/14] net: ethtool: Add support for tsconfig command to get/set hwtstamp config

From: Jakub Kicinski <[email-masked]>
Date: Mon, 15 Jul 2024 07:59:26 -0700

On Tue, 09 Jul 2024 15:53:45 +0200 Kory Maincent wrote:
> +	/* Get the hwtstamp config from netlink */
> +	if (tb[ETHTOOL_A_TSCONFIG_TX_TYPES]) {
> +		ret = ethnl_parse_bitset(&req_tx_type, &mask,
> +					 __HWTSTAMP_TX_CNT,
> +					 tb[ETHTOOL_A_TSCONFIG_TX_TYPES],
> +					 ts_tx_type_names, info->extack);
> +		if (ret < 0)
> +			goto err_clock_put;
> +
> +		/* Select only one tx type at a time */
> +		if (ffs(req_tx_type) != fls(req_tx_type)) {
> +			ret = -EINVAL;
> +			goto err_clock_put;
> +		}
> +
> +		hwtst_config.tx_type = ffs(req_tx_type) - 1;
> +	}
> +	if (tb[ETHTOOL_A_TSCONFIG_RX_FILTERS]) {
> +		ret = ethnl_parse_bitset(&req_rx_filter, &mask,
> +					 __HWTSTAMP_FILTER_CNT,
> +					 tb[ETHTOOL_A_TSCONFIG_RX_FILTERS],
> +					 ts_rx_filter_names, info->extack);
> +		if (ret < 0)
> +			goto err_clock_put;
> +
> +		/* Select only one rx filter at a time */
> +		if (ffs(req_rx_filter) != fls(req_rx_filter)) {
> +			ret = -EINVAL;
> +			goto err_clock_put;
> +		}
> +
> +		hwtst_config.rx_filter = ffs(req_rx_filter) - 1;
> +	}
> +	if (tb[ETHTOOL_A_TSCONFIG_HWTSTAMP_FLAGS]) {
> +		ret = nla_get_u32(tb[ETHTOOL_A_TSCONFIG_HWTSTAMP_FLAGS]);
> +		if (ret < 0)
> +			goto err_clock_put;
> +		hwtst_config.flags = ret;
> +	}

We should be tracking mod on these, too. Separately from the provider
mod bit, let's not call the driver and send notification if nothing
changed.

> +	ret = net_hwtstamp_validate(&hwtst_config);
> +	if (ret)
> +		goto err_clock_put;
> +
> +	/* Disable current time stamping if we try to enable another one */
> +	if (mod && (hwtst_config.tx_type || hwtst_config.rx_filter)) {
> +		struct kernel_hwtstamp_config zero_config = {0};
> +
> +		ret = dev_set_hwtstamp_phylib(dev, &zero_config, info->extack);
> +		if (ret < 0)
> +			goto err_clock_put;
> +	}
> +
> +	/* Changed the selected hwtstamp source if needed */
> +	if (mod) {
> +		struct hwtstamp_provider *__hwtstamp;
> +
> +		__hwtstamp = rcu_replace_pointer_rtnl(dev->hwtstamp, hwtstamp);
> +		if (__hwtstamp)
> +			call_rcu(&__hwtstamp->rcu_head,
> +				 remove_hwtstamp_provider);
> +	}
> +
> +	ret = dev_set_hwtstamp_phylib(dev, &hwtst_config, info->extack);
> +	if (ret < 0)
> +		return ret;

We can't unwind to old state here?

> +	return 1;

Driver can change hwtst_config right? "upgrade" the rx_filter 
to a broader one, IIRC. Shouldn't we reply to the set command with 
the resulting configuration, in case it changed? Basically provide 
the same info as the notification would.