backend-drm: handle multiple drm nodes with logind

When using logind launcher, we receive a PauseDevice "gone" message
from logind session management for each device we close while looking
for KMS devices.

Make logind notify the backend of the device add/remove so that the
backend can decide what to do, instead of assuming that if it is a
DRM_MAJOR device the session should be (de)activated. The backend can
then react to its specific device.

Fixes #251

Signed-off-by: Robert Beckett <bob.beckett@collabora.com>

include/libweston/libweston.h

@@ -1034,6 +1034,19 @@ struct weston_backend {
 	struct weston_output *
 	(*create_output)(struct weston_compositor *compositor,
 			 const char *name);
+
+	/** Notify of device addition/removal
+	 *
+	 * @param compositor The compositor.
+	 * @param device The device that has changed.
+	 * @param added Where it was added (or removed)
+	 *
+	 * Called when a device has been added/removed from the session.
+	 * The backend can decide what to do based on whether it is a
+	 * device that it is controlling or not.
+	 */
+	void (*device_changed)(struct weston_compositor *compositor,
+			       dev_t device, bool added);
 };
 
 /** Callback for saving calibration

libweston/backend-drm/drm.c

@@ -310,6 +310,7 @@ struct drm_backend {
 		int id;
 		int fd;
 		char *filename;
+		dev_t devnum;
 	} drm;
 	struct gbm_device *gbm;
 	struct wl_listener session_listener;
@@ -6840,6 +6841,30 @@ session_notify(struct wl_listener *listener, void *data)
 	}
 }
 
+
+/**
+ * Handle KMS GPU being added/removed
+ *
+ * If the device being added/removed is the KMS device, we activate/deactivate
+ * the compositor session.
+ *
+ * @param compositor The compositor instance.
+ * @param device The device being added/removed.
+ * @param added Whether the device is being added (or removed)
+ */
+static void
+drm_device_changed(struct weston_compositor *compositor,
+		dev_t device, bool added)
+{
+	struct drm_backend *b = to_drm_backend(compositor);
+
+	if (b->drm.fd < 0 || b->drm.devnum != device)
+		return;
+
+	compositor->session_active = added;
+	wl_signal_emit(&compositor->session_signal, compositor);
+}
+
 /**
  * Determines whether or not a device is capable of modesetting. If successful,
  * sets b->drm.fd and b->drm.filename to the opened device.
@@ -6849,6 +6874,7 @@ drm_device_is_kms(struct drm_backend *b, struct udev_device *device)
 {
 	const char *filename = udev_device_get_devnode(device);
 	const char *sysnum = udev_device_get_sysnum(device);
+	dev_t devnum = udev_device_get_devnum(device);
 	drmModeRes *res;
 	int id = -1, fd;
 
@@ -6883,6 +6909,7 @@ drm_device_is_kms(struct drm_backend *b, struct udev_device *device)
 	b->drm.fd = fd;
 	b->drm.id = id;
 	b->drm.filename = strdup(filename);
+	b->drm.devnum = devnum;
 
 	drmModeFreeResources(res);
 
@@ -7558,6 +7585,7 @@ drm_backend_create(struct weston_compositor *compositor,
 	b->base.repaint_flush = drm_repaint_flush;
 	b->base.repaint_cancel = drm_repaint_cancel;
 	b->base.create_output = drm_output_create;
+	b->base.device_changed = drm_device_changed;
 
 	weston_setup_vt_switch_bindings(compositor);
 

libweston/launcher-logind.c

@@ -488,20 +488,21 @@ device_paused(struct launcher_logind *wl, DBusMessage *m)
 	if (!strcmp(type, "pause"))
 		launcher_logind_pause_device_complete(wl, major, minor);
 
-	if (wl->sync_drm && major == DRM_MAJOR)
-		launcher_logind_set_active(wl, false);
+	if (wl->sync_drm && wl->compositor->backend->device_changed)
+		wl->compositor->backend->device_changed(wl->compositor,
+							makedev(major,minor),
+							false);
 }
 
 static void
 device_resumed(struct launcher_logind *wl, DBusMessage *m)
 {
 	bool r;
-	uint32_t major;
+	uint32_t major, minor;
 
 	r = dbus_message_get_args(m, NULL,
 				  DBUS_TYPE_UINT32, &major,
-				  /*DBUS_TYPE_UINT32, &minor,
-				  DBUS_TYPE_UNIX_FD, &fd,*/
+				  DBUS_TYPE_UINT32, &minor,
 				  DBUS_TYPE_INVALID);
 	if (!r) {
 		weston_log("logind: cannot parse ResumeDevice dbus signal\n");
@@ -514,8 +515,10 @@ device_resumed(struct launcher_logind *wl, DBusMessage *m)
 	 * there is no need for us to handle this event for evdev. For DRM, we
 	 * notify the compositor to wake up. */
 
-	if (wl->sync_drm && major == DRM_MAJOR)
-		launcher_logind_set_active(wl, true);
+	if (wl->sync_drm && wl->compositor->backend->device_changed)
+		wl->compositor->backend->device_changed(wl->compositor,
+							makedev(major,minor),
+							true);
 }
 
 static DBusHandlerResult