bus/vdev: add custom scan hook

The scan callback allows to spawn a vdev automatically
given some custom scan rules.
It is especially useful to create a TAP device automatically
connected to a netdevice as remote.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Jianfeng Tan <jianfeng.tan@intel.com>

drivers/bus/vdev/rte_bus_vdev.h

@@ -124,6 +124,41 @@ RTE_PMD_EXPORT_NAME(nm, __COUNTER__)
 #define RTE_PMD_REGISTER_ALIAS(nm, alias)\
 static const char *vdrvinit_ ## nm ## _alias = RTE_STR(alias)
 
+typedef void (*rte_vdev_scan_callback)(void *user_arg);
+
+/**
+ * Add a callback to be called on vdev scan
+ * before reading the devargs list.
+ *
+ * This function cannot be called in a scan callback
+ * because of deadlock.
+ *
+ * @param callback
+ *   The function to be called which can update the devargs list.
+ * @param user_arg
+ *   An opaque pointer passed to callback.
+ * @return
+ *   0 on success, negative on error
+ */
+int
+rte_vdev_add_custom_scan(rte_vdev_scan_callback callback, void *user_arg);
+
+/**
+ * Remove a registered scan callback.
+ *
+ * This function cannot be called in a scan callback
+ * because of deadlock.
+ *
+ * @param callback
+ *   The registered function to be removed.
+ * @param user_arg
+ *   The associated opaque pointer or (void*)-1 for any.
+ * @return
+ *   0 on success
+ */
+int
+rte_vdev_remove_custom_scan(rte_vdev_scan_callback callback, void *user_arg);
+
 /**
  * Initialize a driver specified by name.
  *

drivers/bus/vdev/rte_bus_vdev_version.map

@@ -8,3 +8,11 @@ DPDK_17.11 {
 
 	local: *;
 };
+
+DPDK_18.02 {
+	global:
+
+	rte_vdev_add_custom_scan;
+	rte_vdev_remove_custom_scan;
+
+} DPDK_17.11;

drivers/bus/vdev/vdev.c

@@ -44,6 +44,8 @@
 #include <rte_common.h>
 #include <rte_devargs.h>
 #include <rte_memory.h>
+#include <rte_tailq.h>
+#include <rte_spinlock.h>
 #include <rte_errno.h>
 
 #include "rte_bus_vdev.h"
@@ -62,6 +64,16 @@ static struct vdev_device_list vdev_device_list =
 struct vdev_driver_list vdev_driver_list =
 	TAILQ_HEAD_INITIALIZER(vdev_driver_list);
 
+struct vdev_custom_scan {
+	TAILQ_ENTRY(vdev_custom_scan) next;
+	rte_vdev_scan_callback callback;
+	void *user_arg;
+};
+TAILQ_HEAD(vdev_custom_scans, vdev_custom_scan);
+static struct vdev_custom_scans vdev_custom_scans =
+	TAILQ_HEAD_INITIALIZER(vdev_custom_scans);
+static rte_spinlock_t vdev_custom_scan_lock = RTE_SPINLOCK_INITIALIZER;
+
 /* register a driver */
 void
 rte_vdev_register(struct rte_vdev_driver *driver)
@@ -76,6 +88,53 @@ rte_vdev_unregister(struct rte_vdev_driver *driver)
 	TAILQ_REMOVE(&vdev_driver_list, driver, next);
 }
 
+int
+rte_vdev_add_custom_scan(rte_vdev_scan_callback callback, void *user_arg)
+{
+	struct vdev_custom_scan *custom_scan;
+
+	rte_spinlock_lock(&vdev_custom_scan_lock);
+
+	/* check if already registered */
+	TAILQ_FOREACH(custom_scan, &vdev_custom_scans, next) {
+		if (custom_scan->callback == callback &&
+				custom_scan->user_arg == user_arg)
+			break;
+	}
+
+	if (custom_scan == NULL) {
+		custom_scan = malloc(sizeof(struct vdev_custom_scan));
+		if (custom_scan != NULL) {
+			custom_scan->callback = callback;
+			custom_scan->user_arg = user_arg;
+			TAILQ_INSERT_TAIL(&vdev_custom_scans, custom_scan, next);
+		}
+	}
+
+	rte_spinlock_unlock(&vdev_custom_scan_lock);
+
+	return (custom_scan == NULL) ? -1 : 0;
+}
+
+int
+rte_vdev_remove_custom_scan(rte_vdev_scan_callback callback, void *user_arg)
+{
+	struct vdev_custom_scan *custom_scan, *tmp_scan;
+
+	rte_spinlock_lock(&vdev_custom_scan_lock);
+	TAILQ_FOREACH_SAFE(custom_scan, &vdev_custom_scans, next, tmp_scan) {
+		if (custom_scan->callback != callback ||
+				(custom_scan->user_arg != (void *)-1 &&
+				custom_scan->user_arg != user_arg))
+			continue;
+		TAILQ_REMOVE(&vdev_custom_scans, custom_scan, next);
+		free(custom_scan);
+	}
+	rte_spinlock_unlock(&vdev_custom_scan_lock);
+
+	return 0;
+}
+
 static int
 vdev_parse(const char *name, void *addr)
 {
@@ -260,6 +319,22 @@ vdev_scan(void)
 {
 	struct rte_vdev_device *dev;
 	struct rte_devargs *devargs;
+	struct vdev_custom_scan *custom_scan;
+
+	/* call custom scan callbacks if any */
+	rte_spinlock_lock(&vdev_custom_scan_lock);
+	TAILQ_FOREACH(custom_scan, &vdev_custom_scans, next) {
+		if (custom_scan->callback != NULL)
+			/*
+			 * the callback should update devargs list
+			 * by calling rte_eal_devargs_insert() with
+			 *     devargs.bus = rte_bus_find_by_name("vdev");
+			 *     devargs.type = RTE_DEVTYPE_VIRTUAL;
+			 *     devargs.policy = RTE_DEV_WHITELISTED;
+			 */
+			custom_scan->callback(custom_scan->user_arg);
+	}
+	rte_spinlock_unlock(&vdev_custom_scan_lock);
 
 	/* for virtual devices we scan the devargs_list populated via cmdline */
 	TAILQ_FOREACH(devargs, &devargs_list, next) {