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

[Stephen Hemminger <stephen@networkplumber.org>]

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@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);
+
+/**
+ * @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);
+
 /**
  * Retrieve the general I/O statistics of an Ethernet device.
  *
-- 
2.11.0