v4l2codecs: Warn user when no media devices are found

Currently if the user is not able to access the devices under /dev/media*,
either due to no media devices present on the system or simply no permission
to access the device, v4l2codecs initialises with no features or debug messages.

Since calling `GST_DEBUG="v4l2*:7" gst-inspect-1.0 v4l2codecs` is a typical way
to diagnose why element(s) failed to enumerate, we should be more verbose here
when the user is not able to access any /dev/media* device. So print a simple
debug message in this case to aid debugging.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3088>

diff --git a/subprojects/gst-plugins-bad/sys/v4l2codecs/gstv4l2codecdevice.c b/subprojects/gst-plugins-bad/sys/v4l2codecs/gstv4l2codecdevice.c
index 7886c79..0497a1a 100644 (file)
--- a/subprojects/gst-plugins-bad/sys/v4l2codecs/gstv4l2codecdevice.c
+++ b/subprojects/gst-plugins-bad/sys/v4l2codecs/gstv4l2codecdevice.c
@@ -316,6 +316,9 @@ gst_v4l2_codec_find_devices (void)
   client = g_udev_client_new (NULL);
   udev_devices = g_udev_client_query_by_subsystem (client, "media");
 
+  if (!udev_devices)
+    GST_DEBUG ("Found no media devices");
+
   for (d = udev_devices; d; d = g_list_next (d)) {
     GUdevDevice *udev = (GUdevDevice *) d->data;
     const gchar *path = g_udev_device_get_device_file (udev);