[media] media-device: split media initialization and registration

The media device node is registered and so made visible to user-space
before entities are registered and links created which means that the
media graph obtained by user-space could be only partially enumerated
if that happens too early before all the graph has been created.

To avoid this race condition, split the media init and registration
in separate functions and only register the media device node when
all the pending subdevices have been registered, either explicitly
by the driver or asynchronously using v4l2_async_register_subdev().

The media_device_register() had a check for drivers not filling dev
and model fields but all drivers in mainline set them and not doing
it will be a driver bug so change the function return to void and
add a BUG_ON() for dev being NULL instead.

Also, add a media_device_cleanup() function that will destroy the
graph_mutex that is initialized in media_device_init().

[mchehab@osg.samsung.com: Fix compilation if !CONFIG_MEDIA_CONTROLLER
 and remove two warnings added by this changeset]
Suggested-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 12 insertions, 11 deletions

diff --git a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c
index 6d3f61f..7f52bcb 100644
--- a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c
+++ b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c
@@ -400,13 +400,12 @@ skip_feed_stop:
 	return ret;
 }
 
-static void dvb_usbv2_media_device_register(struct dvb_usb_adapter *adap)
+static void dvb_usbv2_media_device_init(struct dvb_usb_adapter *adap)
 {
 #ifdef CONFIG_MEDIA_CONTROLLER_DVB
 	struct media_device *mdev;
 	struct dvb_usb_device *d = adap_to_d(adap);
 	struct usb_device *udev = d->udev;
-	int ret;
 
 	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
 	if (!mdev)
@@ -420,19 +419,18 @@ static void dvb_usbv2_media_device_register(struct dvb_usb_adapter *adap)
 	mdev->hw_revision = le16_to_cpu(udev->descriptor.bcdDevice);
 	mdev->driver_version = LINUX_VERSION_CODE;
 
-	ret = media_device_register(mdev);
-	if (ret) {
-		dev_err(&d->udev->dev,
-			"Couldn't create a media device. Error: %d\n",
-			ret);
-		kfree(mdev);
-		return;
-	}
+	media_device_init(mdev);
 
 	dvb_register_media_controller(&adap->dvb_adap, mdev);
 
 	dev_info(&d->udev->dev, "media controller created\n");
+#endif
+}
 
+static void dvb_usbv2_media_device_register(struct dvb_usb_adapter *adap)
+{
+#ifdef CONFIG_MEDIA_CONTROLLER_DVB
+	media_device_register(adap->dvb_adap.mdev);
 #endif
 }
 
@@ -444,6 +442,7 @@ static void dvb_usbv2_media_device_unregister(struct dvb_usb_adapter *adap)
 		return;
 
 	media_device_unregister(adap->dvb_adap.mdev);
+	media_device_cleanup(adap->dvb_adap.mdev);
 	kfree(adap->dvb_adap.mdev);
 	adap->dvb_adap.mdev = NULL;
 
@@ -467,7 +466,7 @@ static int dvb_usbv2_adapter_dvb_init(struct dvb_usb_adapter *adap)
 
 	adap->dvb_adap.priv = adap;
 
-	dvb_usbv2_media_device_register(adap);
+	dvb_usbv2_media_device_init(adap);
 
 	if (d->props->read_mac_address) {
 		ret = d->props->read_mac_address(adap,
@@ -702,6 +701,8 @@ static int dvb_usbv2_adapter_frontend_init(struct dvb_usb_adapter *adap)
 	if (ret < 0)
 		goto err_dvb_unregister_frontend;
 
+	dvb_usbv2_media_device_register(adap);
+
 	return 0;
 
 err_dvb_unregister_frontend: