[dpdk-dev] [PATCH v2 05/18] eal/dev: add device iterator interface

[Gaetan Rivet <gaetan.rivet@6wind.com>]

A device iterator allows iterating over a set of devices.
This set is defined by the two descriptions offered,

  * rte_bus
  * rte_class

Only one description can be provided, or both. It is not allowed to
provide no description at all.

Each layer of abstraction then performs a filter based on the
description provided. This filtering allows iterating on their internal
set of devices, stopping when a match is valid and returning the current
iteration context.

This context allows starting the next iteration from the same point and
going forward.

Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>
---
 lib/librte_eal/common/include/rte_dev.h | 47 +++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/lib/librte_eal/common/include/rte_dev.h b/lib/librte_eal/common/include/rte_dev.h
index b688f1efd..937ff6079 100644
--- a/lib/librte_eal/common/include/rte_dev.h
+++ b/lib/librte_eal/common/include/rte_dev.h
@@ -263,6 +263,53 @@ __attribute__((used)) = str
 static const char DRV_EXP_TAG(name, kmod_dep_export)[] \
 __attribute__((used)) = str
 
+/**
+ * Iteration context.
+ *
+ * This context carries over the current iteration state.
+ */
+struct rte_dev_iterator {
+	const char *devstr; /**< device string. */
+	const char *busstr; /**< bus-related part of device string. */
+	const char *clsstr; /**< class-related part of device string. */
+	struct rte_bus *bus; /**< bus handle. */
+	struct rte_class *cls; /**< class handle. */
+	struct rte_device *device; /**< current position. */
+	void *class_device; /**< additional specialized context. */
+};
+
+/**
+ * Device iteration function.
+ *
+ * Find the next device matching properties passed in parameters.
+ * The function takes an additional ``start`` parameter, that is
+ * used as starting context when relevant.
+ *
+ * The function returns the current element in the iteration.
+ * This return value will potentially be used as a start parameter
+ * in subsequent calls to the function.
+ *
+ * The additional iterator parameter is only there if a specific
+ * implementation needs additional context. It must not be modified by
+ * the iteration function itself.
+ *
+ * @param start
+ *   Starting iteration context.
+ *
+ * @param devstr
+ *   Device description string.
+ *
+ * @param it
+ *   Device iterator.
+ *
+ * @return
+ *   The address of the current element matching the device description
+ *   string.
+ */
+typedef void *(*rte_dev_iterate_t)(const void *start,
+				   const char *devstr,
+				   const struct rte_dev_iterator *it);
+
 #ifdef __cplusplus
 }
 #endif
-- 
2.11.0