media: v4l2-mem2mem: Add a kref to the v4l2_m2m_dev structure

Adding a reference count to the v4l2_m2m_dev structure allow safely
sharing it across multiple hardware nodes. This can be used to prevent
running jobs concurrently on m2m cores that have some internal resource
sharing.

Signed-off-by: Ming Qian <ming.qian@oss.nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
[hverkuil: fix typos in v4l2_m2m_put documentation]

diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index fec93c1a9231712467053a1763e56891772b4e3e..ae0de54d4c3e16a096cfb580fee4bb761b5d2503 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -90,6 +90,7 @@ static const char * const m2m_entity_name[] = {
  * @job_work:          worker to run queued jobs.
  * @job_queue_flags:   flags of the queue status, %QUEUE_PAUSED.
  * @m2m_ops:           driver callbacks
+ * @kref:              device reference count
  */
 struct v4l2_m2m_dev {
        struct v4l2_m2m_ctx     *curr_ctx;
@@ -109,6 +110,8 @@ struct v4l2_m2m_dev {
        unsigned long           job_queue_flags;
 
        const struct v4l2_m2m_ops *m2m_ops;
+
+       struct kref kref;
 };
 
 static struct v4l2_m2m_queue_ctx *get_queue_ctx(struct v4l2_m2m_ctx *m2m_ctx,
@@ -1200,6 +1203,7 @@ struct v4l2_m2m_dev *v4l2_m2m_init(const struct v4l2_m2m_ops *m2m_ops)
        INIT_LIST_HEAD(&m2m_dev->job_queue);
        spin_lock_init(&m2m_dev->job_spinlock);
        INIT_WORK(&m2m_dev->job_work, v4l2_m2m_device_run_work);
+       kref_init(&m2m_dev->kref);
 
        return m2m_dev;
 }
@@ -1211,6 +1215,25 @@ void v4l2_m2m_release(struct v4l2_m2m_dev *m2m_dev)
 }
 EXPORT_SYMBOL_GPL(v4l2_m2m_release);
 
+void v4l2_m2m_get(struct v4l2_m2m_dev *m2m_dev)
+{
+       kref_get(&m2m_dev->kref);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_get);
+
+static void v4l2_m2m_release_from_kref(struct kref *kref)
+{
+       struct v4l2_m2m_dev *m2m_dev = container_of(kref, struct v4l2_m2m_dev, kref);
+
+       v4l2_m2m_release(m2m_dev);
+}
+
+void v4l2_m2m_put(struct v4l2_m2m_dev *m2m_dev)
+{
+       kref_put(&m2m_dev->kref, v4l2_m2m_release_from_kref);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_put);
+
 struct v4l2_m2m_ctx *v4l2_m2m_ctx_init(struct v4l2_m2m_dev *m2m_dev,
                void *drv_priv,
                int (*queue_init)(void *priv, struct vb2_queue *src_vq, struct vb2_queue *dst_vq))

diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index bf6a09a04dcf8407ba770bf6d960aa70a909b07e..31de25d792b98fda1794a1ccab862d64d5c272cd 100644 (file)
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -547,6 +547,27 @@ v4l2_m2m_register_media_controller(struct v4l2_m2m_dev *m2m_dev,
  */
 void v4l2_m2m_release(struct v4l2_m2m_dev *m2m_dev);
 
+/**
+ * v4l2_m2m_get() - take a reference to the m2m_dev structure
+ *
+ * @m2m_dev: opaque pointer to the internal data to handle M2M context
+ *
+ * This is used to share the M2M device across multiple devices. This
+ * can be used to avoid scheduling two hardware nodes concurrently.
+ */
+void v4l2_m2m_get(struct v4l2_m2m_dev *m2m_dev);
+
+/**
+ * v4l2_m2m_put() - remove a reference to the m2m_dev structure
+ *
+ * @m2m_dev: opaque pointer to the internal data to handle M2M context
+ *
+ * Once the M2M device has no more references, v4l2_m2m_release() will be
+ * called automatically. Users of this method should never call
+ * v4l2_m2m_release() directly. See v4l2_m2m_get() for more details.
+ */
+void v4l2_m2m_put(struct v4l2_m2m_dev *m2m_dev);
+
 /**
  * v4l2_m2m_ctx_init() - allocate and initialize a m2m context
  *