linux-kernel - [RFC PATCH] media: rcar-vin: Allow independent VIN link enablement

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Message-Id: <20181225232725.15935-1-slongerbeam@gmail.com>
Date:   Tue, 25 Dec 2018 15:27:25 -0800
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     linux-media@...r.kernel.org
Cc:     Steve Longerbeam <slongerbeam@...il.com>,
        Niklas Söderlund <niklas.soderlund@...natech.se>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-renesas-soc@...r.kernel.org (open list:MEDIA DRIVERS FOR RENESAS
        - VIN), linux-kernel@...r.kernel.org (open list)
Subject: [RFC PATCH] media: rcar-vin: Allow independent VIN link enablement

There is a block of code in rvin_group_link_notify() that prevents
enabling a link to a VIN node if any entity in the media graph is
in use. This prevents enabling a VIN link even if there is an in-use
entity somewhere in the graph that is independent of the link's
pipeline.

For example, the code block will prevent enabling a link from
the first rcar-csi2 receiver to a VIN node even if there is an
enabled link somewhere far upstream on the second independent
rcar-csi2 receiver pipeline.

If this code block is meant to prevent modifying a link if the
link is actively involved in streaming, there is already such a
check in __media_entity_setup_link() that verifies the stream_count
of the link's source and sink entities are both zero.

Remove the code block so that VIN node links can be enabled even if
there are other independent in-use entities.

Fixes: c0cc5aef31 ("media: rcar-vin: add link notify for Gen3")

Signed-off-by: Steve Longerbeam <slongerbeam@...il.com>
---
 drivers/media/platform/rcar-vin/rcar-core.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c
index f0719ce24b97..b2c9a876969e 100644
--- a/drivers/media/platform/rcar-vin/rcar-core.c
+++ b/drivers/media/platform/rcar-vin/rcar-core.c
@@ -116,7 +116,6 @@ static int rvin_group_link_notify(struct media_link *link, u32 flags,
 						struct rvin_group, mdev);
 	unsigned int master_id, channel, mask_new, i;
 	unsigned int mask = ~0;
-	struct media_entity *entity;
 	struct video_device *vdev;
 	struct media_pad *csi_pad;
 	struct rvin_dev *vin = NULL;
@@ -131,11 +130,6 @@ static int rvin_group_link_notify(struct media_link *link, u32 flags,
 	    !is_media_entity_v4l2_video_device(link->sink->entity))
 		return 0;

-	/* If any entity is in use don't allow link changes. */
-	media_device_for_each_entity(entity, &group->mdev)
-		if (entity->use_count)
-			return -EBUSY;
-
 	mutex_lock(&group->lock);

 	/* Find the master VIN that controls the routes. */
-- 
2.17.1