[libvirt] [PATCH RFC 32/32] Add nomatch filters when enumerating udev devices

[Ján Tomko]

Filter out some subsystems we are not interested in.
---
After the netdev cleanups, this speeds up the driver initialization from 18 ms to 13 ms,
which is percentually a lot, but neligible in absolute times.

This patch uses a negative filter because I could not find an exhaustive list of possible subsystems.
A positive filter could be applied to udev_monitor as well.

 src/node_device/node_device_udev.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
index b46fec6..2e86230 100644
--- a/src/node_device/node_device_udev.c
+++ b/src/node_device/node_device_udev.c
@@ -1167,13 +1167,34 @@ static int udevProcessDeviceListEntry(struct udev *udev,
 }
 
 
+const char *subsystem_blacklist[] = {
+    "acpi", "tty", "vc", "i2c",
+};
+
+static int udevEnumerateAddMatches(struct udev_enumerate *udev_enumerate)
+{
+    size_t i;
+
+    for (i = 0; i < ARRAY_CARDINALITY(subsystem_blacklist); i++) {
+        const char *s = subsystem_blacklist[i];
+        if (udev_enumerate_add_nomatch_subsystem(udev_enumerate, s) < 0) {
+            virReportSystemError(errno, "%s", _("failed to add susbsystem filter"));
+            return -1;
+        }
+    }
+    return 0;
+}
+
+
 static int udevEnumerateDevices(struct udev *udev)
 {
     struct udev_enumerate *udev_enumerate = NULL;
     struct udev_list_entry *list_entry = NULL;
-    int ret = 0;
+    int ret = -1;
 
     udev_enumerate = udev_enumerate_new(udev);
+    if (udevEnumerateAddMatches(udev_enumerate) < 0)
+        goto cleanup;
 
     ret = udev_enumerate_scan_devices(udev_enumerate);
     if (ret != 0) {
-- 
2.7.3