evdev: warn about missing input devices

Usually there should be at least one input device, when Weston starts
up, or is reactivated by a VT switch. Add a nice warning, in case there
are no input devices.

This is to give a clue to users who happen to try Weston on DRM, and
do not get any response.

Add also a message to another failure case, that may lead to missing
input devices.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

diff --git a/src/evdev.c b/src/evdev.c
index 0b2fdfa..39e04d8 100644 (file)
--- a/src/evdev.c
+++ b/src/evdev.c
@@ -545,6 +545,16 @@ evdev_add_devices(struct udev *udev, struct weston_input_device *input_base)
                udev_device_unref(device);
        }
        udev_enumerate_unref(e);
+
+       if (wl_list_empty(&input->devices_list)) {
+               fprintf(stderr,
+                       "warning: no input devices on entering Weston. "
+                       "Possible causes:\n"
+                       "\t- no permissions to read /dev/input/evdev*\n"
+                       "\t- seats misconfigured "
+                       "(Weston backend option 'seat', "
+                       "udev device property ID_SEAT)\n");
+       }
 }
 
 static int
@@ -581,8 +591,10 @@ evdev_config_udev_monitor(struct udev *udev, struct evdev_input *master)
        struct weston_compositor *c = master->base.compositor;
 
        master->udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
-       if (!master->udev_monitor)
+       if (!master->udev_monitor) {
+               fprintf(stderr, "udev: failed to create the udev monitor\n");
                return 0;
+       }
 
        udev_monitor_filter_add_match_subsystem_devtype(master->udev_monitor,
                        "input", NULL);