Re: [PATCH v2 3/3] ethdev: add the check for the valitity of timestamp offload

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 7/2/22 11:17, Dongdong Liu wrote:
> From: Huisong Li <lihuisong@huawei.com>
> 
> This patch adds the check for the valitity of timestamp offload.
> 
> Signed-off-by: Huisong Li <lihuisong@huawei.com>
> Signed-off-by: Dongdong Liu <liudongdong3@huawei.com>
> ---
>   lib/ethdev/rte_ethdev.c | 65 ++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 64 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
> index 1979dc0850..9b8ba3a348 100644
> --- a/lib/ethdev/rte_ethdev.c
> +++ b/lib/ethdev/rte_ethdev.c
> @@ -5167,15 +5167,48 @@ rte_eth_dev_set_mc_addr_list(uint16_t port_id,
>   						mc_addr_set, nb_mc_addr));
>   }
>   
> +static int
> +rte_eth_timestamp_offload_valid(struct rte_eth_dev *dev)
> +{
> +	struct rte_eth_dev_info dev_info;
> +	struct rte_eth_rxmode *rxmode;
> +	int ret;
> +
> +	ret = rte_eth_dev_info_get(dev->data->port_id, &dev_info);
> +	if (ret != 0) {
> +		RTE_ETHDEV_LOG(ERR, "Cannot get port (%u) device information.\n",
> +			       dev->data->port_id);
> +		return ret;
> +	}
> +
> +	if ((dev_info.rx_offload_capa & RTE_ETH_RX_OFFLOAD_TIMESTAMP) == 0) {

As I understand strictly speaking the Rx offload is not the same as PTP
support. May be it is a corner case, but I can imagine case when HW
cannot provide timestamp for each packet (lack of space in extra
information associated with a packet), but can return timestamps
out-of-band using timestamp get API.

I have no strong opinion. May be we are not interested in the corner
case, but I think it requires acks from maintainers of all drivers
which support PTP.

> +		RTE_ETHDEV_LOG(ERR, "Driver does not support PTP.\n");
> +		return -ENOTSUP;
> +	}
> +
> +	rxmode = &dev->data->dev_conf.rxmode;
> +	if ((rxmode->offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP) == 0) {
> +		RTE_ETHDEV_LOG(ERR, "Please enable 'RTE_ETH_RX_OFFLOAD_TIMESTAMP' offload.\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
>   int
>   rte_eth_timesync_enable(uint16_t port_id)
>   {
>   	struct rte_eth_dev *dev;
> +	int ret;
>   
>   	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
>   	dev = &rte_eth_devices[port_id];
>   
>   	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->timesync_enable, -ENOTSUP);
> +	ret = rte_eth_timestamp_offload_valid(dev);
> +	if (ret != 0)
> +		return ret;
> +

Typically ops pointer check is done just before usage. So, it is
better to avoid adding code between check and usage.
Same in all cases below.
if there is a good reason to do so, please, explain it.

>   	return eth_err(port_id, (*dev->dev_ops->timesync_enable)(dev));
>   }
>   

[snip]