Re: [PATCH 1/2] ethdev: add capability control API

The rte_flow feature breaks the current monolithic approach for ethdev and
introduces the new generic flow API to ethdev using a plugin-like approach.

Basically, the rte_flow API is still logically part of ethdev:
- It extends the ethdev functionality: rte_flow is a new feature/capability
  of ethdev;
- all its functions work on an Ethernet device: the first parameter of the
  rte_flow functions is Ethernet device port ID.

At the same time, the rte_flow API is a sort of capability plugin for ethdev:
- the rte_flow API functions have their own name space: they are called
  rte_flow_operationXYZ() as opposed to rte_eth_dev_flow_operationXYZ());
- the rte_flow API functions are placed in separate files in the same
  librte_ether folder as opposed to rte_ethdev.[hc].

The way it works is by using the existing ethdev API function
rte_eth_dev_filter_ctrl() to query the current Ethernet device port ID for the
support of the rte_flow capability and return the pointer to the
rte_flow operations when supported and NULL otherwise:

struct rte_flow_ops *eth_flow_ops;
int rte = rte_eth_dev_filter_ctrl(eth_port_id,
	RTE_ETH_FILTER_GENERIC, RTE_ETH_FILTER_GET, &eth_flow_ops);

Unfortunately, the rte_flow opportunistically uses the rte_eth_dev_filter_ctrl()
API function, which is applicable just to RX-side filters as opposed to
introducing a mechanism that could be used by any capability in a generic way.

This is the gap that addressed by the current patch. This mechanism is intended
to be used to introduce new capabilities into ethdev in a modular plugin-like
approach, such as hierarchical scheduler. Over time, if agreed, it can also be
used for exposing the existing Ethernet device capabilities in a modular way,
such as: xstats, filters, multicast, mirroring, tunnels, time stamping, eeprom,
bypass, etc.

Signed-off-by: Cristian Dumitrescu <redacted>
---
 lib/librte_ether/rte_ethdev.c          | 13 +++++++++++++
 lib/librte_ether/rte_ethdev.h          | 29 +++++++++++++++++++++++++++++
 lib/librte_ether/rte_ether_version.map |  7 +++++++
 3 files changed, 49 insertions(+)

diff --git a/lib/librte_ether/rte_ethdev.c b/lib/librte_ether/rte_ethdev.c
index eb0a94a..ae187c4 100644
--- a/lib/librte_ether/rte_ethdev.c
+++ b/lib/librte_ether/rte_ethdev.c

@@ -2802,6 +2802,19 @@ rte_eth_dev_filter_ctrl(uint8_t port_id, enum rte_filter_type filter_type,
 	return (*dev->dev_ops->filter_ctrl)(dev, filter_type, filter_op, arg);
 }
 
+int
+rte_eth_dev_capability_control(uint8_t port_id, enum rte_eth_capability cap,
+	void *arg)
+{
+	struct rte_eth_dev *dev;
+
+	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->cap_ctrl, -ENOTSUP);
+	return (*dev->dev_ops->cap_ctrl)(dev, cap, arg);
+}
+
 void *
 rte_eth_add_rx_callback(uint8_t port_id, uint16_t queue_id,
 		rte_rx_callback_fn fn, void *user_param)

diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
index c17bbda..43ffb9e 100644
--- a/lib/librte_ether/rte_ethdev.h
+++ b/lib/librte_ether/rte_ethdev.h

@@ -1073,6 +1073,12 @@ TAILQ_HEAD(rte_eth_dev_cb_list, rte_eth_dev_callback);
  * structure associated with an Ethernet device.
  */
 
+enum rte_eth_capability {
+	RTE_ETH_CAPABILITY_FLOW = 0, /**< Flow */
+	RTE_ETH_CAPABILITY_SCHED, /**< Hierarchical Scheduler */
+	RTE_ETH_CAPABILITY_MAX
+};