linux-kernel - [PATCH v2 3/3] media: vimc: Join pipeline if one already exists

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Date:   Fri, 24 Jul 2020 17:32:13 +0530
From:   Kaaira Gupta <kgupta@...iitr.ac.in>
To:     Helen Koike <helen.koike@...labora.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Niklas Söderlund <niklas.soderlund@...natech.se>
Cc:     Kaaira Gupta <kgupta@...iitr.ac.in>
Subject: [PATCH v2 3/3] media: vimc: Join pipeline if one already exists

An output which is running is already part of a pipeline and trying to
start a new pipeline is not possible. This prevents two capture devices
from streaming at the same time.

Instead of failing to start the second capture device allow it to join
the already running pipeline. This allows two (or more) capture devices
to independently be started and stopped.

[Kaaira: Changed the search for an existing connected sensor, to search
for a non-NULL pipe instead, this helps to terminate the search at
output itself instead of going till the sensor, changed variable names,
commit message and conditions accordingly]

Signed-off-by: Niklas Söderlund <niklas.soderlund@...natech.se>
Signed-off-by: Kaaira Gupta <kgupta@...iitr.ac.in>
---
 .../media/test-drivers/vimc/vimc-capture.c    | 35 ++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/media/test-drivers/vimc/vimc-capture.c b/drivers/media/test-drivers/vimc/vimc-capture.c
index c63496b17b9a..423d5e5a508d 100644
--- a/drivers/media/test-drivers/vimc/vimc-capture.c
+++ b/drivers/media/test-drivers/vimc/vimc-capture.c
@@ -237,16 +237,49 @@ static void vimc_cap_return_all_buffers(struct vimc_cap_device *vcap,
 	spin_unlock(&vcap->qlock);
 }
 
+static struct media_entity *vimc_cap_get_output(struct vimc_cap_device *vcap)
+{
+	struct media_entity *entity = &vcap->vdev.entity;
+	struct media_device *mdev = entity->graph_obj.mdev;
+	struct media_graph graph;
+
+	mutex_lock(&mdev->graph_mutex);
+	if (media_graph_walk_init(&graph, mdev)) {
+		mutex_unlock(&mdev->graph_mutex);
+		return NULL;
+	}
+
+	media_graph_walk_start(&graph, entity);
+
+	while ((entity = media_graph_walk_next(&graph)))
+		if (entity->pipe)
+			break;
+
+	mutex_unlock(&mdev->graph_mutex);
+
+	media_graph_walk_cleanup(&graph);
+
+	return entity;
+}
+
 static int vimc_cap_start_streaming(struct vb2_queue *vq, unsigned int count)
 {
 	struct vimc_cap_device *vcap = vb2_get_drv_priv(vq);
 	struct media_entity *entity = &vcap->vdev.entity;
+	struct media_pipeline *pipe = NULL;
+	struct media_entity *oent;
 	int ret;
 
 	vcap->sequence = 0;
 
 	/* Start the media pipeline */
-	ret = media_pipeline_start(entity, &vcap->stream.pipe);
+	oent = vimc_cap_get_output(vcap);
+	if (oent)
+		pipe = oent->pipe;
+	else
+		pipe = &vcap->stream.pipe;
+
+	ret = media_pipeline_start(entity, pipe);
 	if (ret) {
 		vimc_cap_return_all_buffers(vcap, VB2_BUF_STATE_QUEUED);
 		return ret;
-- 
2.17.1