[dpdk-dev] [RFC 01/14] ethdev: add link status read/write functions

[Yang, Qiming]

> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Stephen Hemminger
> Sent: Saturday, July 15, 2017 2:30 AM
> To: dev at dpdk.org
> Cc: Stephen Hemminger <stephen at networkplumber.org>; Stephen Hemminger
> <sthemmin at microsoft.com>
> Subject: [dpdk-dev] [RFC 01/14] ethdev: add link status read/write functions
> 
> Many drivers are all doing copy/paste of the same code to atomicly update the
> link status. Reduce duplication, and allow for future changes by having common
> function for this.
> 
> Signed-off-by: Stephen Hemminger <sthemmin at microsoft.com>
> ---
>  lib/librte_ether/rte_ethdev.c | 36 ++++++++++++++++++++++++++++++++++++
>  lib/librte_ether/rte_ethdev.h | 28 ++++++++++++++++++++++++++++
>  2 files changed, 64 insertions(+)
> 
> diff --git a/lib/librte_ether/rte_ethdev.c b/lib/librte_ether/rte_ethdev.c index
> a1b744704f3a..7532fc6b65f0 100644
> --- a/lib/librte_ether/rte_ethdev.c
> +++ b/lib/librte_ether/rte_ethdev.c
> @@ -1332,6 +1332,42 @@ rte_eth_link_get_nowait(uint8_t port_id, struct
> rte_eth_link *eth_link)  }
> 
>  int
> +_rte_eth_link_update(struct rte_eth_dev *dev,
> +		    const struct rte_eth_link *link)
> +{
> +	volatile struct rte_eth_link *dev_link = &(dev->data->dev_link);
> +	struct rte_eth_link old;
> +
> +	RTE_BUILD_BUG_ON(sizeof(*link) != sizeof(uint64_t));
> +
> +	old = *dev_link;
> +
> +	/* Only reason we use cmpset rather than set is
> +	 * that on some architecture may use sign bit as a flag value.
> +	 */
> +	while (rte_atomic64_cmpset((volatile uint64_t *)dev_link,
> +				    *(volatile uint64_t *)dev_link,
> +				   *(const uint64_t *)link) == 0)
> +		continue;
> +
> +	return (old.link_status == link->link_status) ? -1 : 0; }
> +
> +void _rte_eth_link_read(struct rte_eth_dev *dev,
> +			struct rte_eth_link *link)
> +{
> +	const uint64_t *src = (const uint64_t *)&(dev->data->dev_link);
> +	volatile uint64_t *dst = (uint64_t *)link;
> +
> +	RTE_BUILD_BUG_ON(sizeof(*link) != sizeof(uint64_t));
> +
> +	/* Note: this should never fail since both destination and expected
> +	 * values are the same and are a pointer from caller.
> +	 */
> +	rte_atomic64_cmpset(dst, *dst, *src);
> +}
> +
> +int
>  rte_eth_stats_get(uint8_t port_id, struct rte_eth_stats *stats)  {
>  	struct rte_eth_dev *dev;
> diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h index
> f6837278521c..974657933f23 100644
> --- a/lib/librte_ether/rte_ethdev.h
> +++ b/lib/librte_ether/rte_ethdev.h
> @@ -2219,6 +2219,34 @@ void rte_eth_link_get(uint8_t port_id, struct
> rte_eth_link *link);
>   */
>  void rte_eth_link_get_nowait(uint8_t port_id, struct rte_eth_link *link);
> 
> +
> +/**
> + * @internal
> + * Atomically write the link status for the specific device.
> + * It is for use by DPDK device driver use only.
> + * User applications should not call it
> + *
> + * @param dev
> + *  Pointer to struct rte_eth_dev.
> + * @param link
> + *  New link status value.
> + * @return
> + *  -1 if link state has changed, 0 if the same.
> + */
> +int _rte_eth_link_update(struct rte_eth_dev *dev,
> +			 const struct rte_eth_link *link);
> +
This function is only do the atomically write, what do you think to change the function name to _rte_eth_atomic_write_link_status,
Use name link_update makes me confused, and mix up it with dev_ops link_update.
> +/**
> + * @internal
> + * Atomically read the link speed and status.
> + * @param dev
> + *  Pointer to struct rte_eth_dev.
> + * @param link
> + *  link status value.
> + */
> +void _rte_eth_link_read(struct rte_eth_dev *dev,
> +			struct rte_eth_link *link);
> +
This name is also not very clear. I think change to _rte_eth_atomic_read_link_status will better.
>  /**
>   * Retrieve the general I/O statistics of an Ethernet device.
>   *
> --
> 2.11.0