bus: add iterator to find a bus

This helper allows to iterate over all registered buses and find one
matching data used as parameter.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>

lib/librte_eal/bsdapp/eal/rte_eal_version.map

@@ -193,3 +193,10 @@ DPDK_17.05 {
 	vfio_get_group_no;
 
 } DPDK_17.02;
+
+DPDK_17.08 {
+	global:
+
+	rte_bus_find;
+
+} DPDK_17.05;

lib/librte_eal/common/eal_common_bus.c

@@ -145,3 +145,22 @@ rte_bus_dump(FILE *f)
 		}
 	}
 }
+
+struct rte_bus *
+rte_bus_find(const struct rte_bus *start, rte_bus_cmp_t cmp,
+	     const void *data)
+{
+	struct rte_bus *bus = NULL;
+	bool start_found = !start;
+
+	TAILQ_FOREACH(bus, &rte_bus_list, next) {
+		if (!start_found) {
+			if (bus == start)
+				start_found = 1;
+			continue;
+		}
+		if (cmp(bus, data) == 0)
+			break;
+	}
+	return bus;
+}

lib/librte_eal/common/include/rte_bus.h

@@ -140,6 +140,48 @@ int rte_bus_probe(void);
  */
 void rte_bus_dump(FILE *f);
 
+/**
+ * Bus comparison function.
+ *
+ * @param bus
+ *	Bus under test.
+ *
+ * @param data
+ *	Data to compare against.
+ *
+ * @return
+ *	0 if the bus matches the data.
+ *	!0 if the bus does not match.
+ *	<0 if ordering is possible and the bus is lower than the data.
+ *	>0 if ordering is possible and the bus is greater than the data.
+ */
+typedef int (*rte_bus_cmp_t)(const struct rte_bus *bus, const void *data);
+
+/**
+ * Bus iterator to find a particular bus.
+ *
+ * This function compares each registered bus to find one that matches
+ * the data passed as parameter.
+ *
+ * If the comparison function returns zero this function will stop iterating
+ * over any more buses. To continue a search the bus of a previous search can
+ * be passed via the start parameter.
+ *
+ * @param start
+ *	Starting point for the iteration.
+ *
+ * @param cmp
+ *	Comparison function.
+ *
+ * @param data
+ *	 Data to pass to comparison function.
+ *
+ * @return
+ *	 A pointer to a rte_bus structure or NULL in case no bus matches
+ */
+struct rte_bus *rte_bus_find(const struct rte_bus *start, rte_bus_cmp_t cmp,
+			     const void *data);
+
 /**
  * Helper for Bus registration.
  * The constructor has higher priority than PMD constructors.

lib/librte_eal/linuxapp/eal/rte_eal_version.map

@@ -198,3 +198,10 @@ DPDK_17.05 {
 	vfio_get_group_no;
 
 } DPDK_17.02;
+
+DPDK_17.08 {
+	global:
+
+	rte_bus_find;
+
+} DPDK_17.05;