linux-kernel - [PATCH v5 1/3] [media] media-device: check before unregister if mdev was registered

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Date:	Fri, 11 Dec 2015 19:57:07 -0300
From:	Javier Martinez Canillas <javier@....samsung.com>
To:	linux-kernel@...r.kernel.org
Cc:	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Shuah Khan <shuahkh@....samsung.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Hans Verkuil <hans.verkuil@...co.com>,
	linux-media@...r.kernel.org,
	Javier Martinez Canillas <javier@....samsung.com>
Subject: [PATCH v5 1/3] [media] media-device: check before unregister if mdev was registered

Most media functions that unregister, check if the corresponding register
function succeed before. So these functions can safely be called even if a
registration was never made or the component as already been unregistered.

Add the same check to media_device_unregister() function for consistency.

This will also allow to split the media_device_register() function in an
initialization and registration functions without the need to change the
generic cleanup functions and error code paths for all the media drivers.

Suggested-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
Acked-by: Sakari Ailus <sakari.ailus@...ux.intel.com>

---

Changes in v5: None
Changes in v4: None
Changes in v3: None
Changes in v2:
- Reword the documentation for media_device_unregister(). Suggested by Sakari.
- Added Sakari's Acked-by tag for patch #1.

 drivers/media/media-device.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
index c12481c753a0..11c1c7383361 100644
--- a/drivers/media/media-device.c
+++ b/drivers/media/media-device.c
@@ -577,6 +577,8 @@ EXPORT_SYMBOL_GPL(__media_device_register);
  * media_device_unregister - unregister a media device
  * @mdev:	The media device
  *
+ * It is safe to call this function on an unregistered
+ * (but initialised) media device.
  */
 void media_device_unregister(struct media_device *mdev)
 {
@@ -584,6 +586,10 @@ void media_device_unregister(struct media_device *mdev)
 	struct media_entity *next;
 	struct media_interface *intf, *tmp_intf;
 
+	/* Check if mdev was ever registered at all */
+	if (!media_devnode_is_registered(&mdev->devnode))
+		return;
+
 	/* Remove all entities from the media device */
 	list_for_each_entry_safe(entity, next, &mdev->entities, graph_obj.list)
 		media_device_unregister_entity(entity);
-- 
2.4.3

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