media: Split v4l2_pipeline_pm_use into v4l2_pipeline_pm_{get, put}

Currently, v4l2_pipeline_pm_use() prototype is:

  int v4l2_pipeline_pm_use(struct media_entity *entity, int use)

Where the 'use' argument shall only be set to '1' for enable/power-on,
or to '0' for disable/power-off. The integer return is specified
as only meaningful when 'use' is set to '1'.

Let's enforce this semantic by splitting the function in two:
v4l2_pipeline_pm_get and v4l2_pipeline_pm_put. This is done
for several reasons.

It makes the API easier to use (or harder to misuse).
It removes the constraint on the values the 'use' argument
shall take. Also, it removes the need to constraint
the return value, by making v4l2_pipeline_pm_put void return.

And last, it's more consistent with other kernel APIs, such
as the runtime pm APIs, which makes the code more symmetric.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 15 insertions, 3 deletions

diff --git a/drivers/media/v4l2-core/v4l2-mc.c b/drivers/media/v4l2-core/v4l2-mc.c
index 014a2a97cadd..0fffdd3ce6a4 100644
--- a/drivers/media/v4l2-core/v4l2-mc.c
+++ b/drivers/media/v4l2-core/v4l2-mc.c
@@ -321,7 +321,7 @@ EXPORT_SYMBOL_GPL(v4l_vb2q_enable_media_source);
  * use_count field stores the total number of users of all video device nodes
  * in the pipeline.
  *
- * The v4l2_pipeline_pm_use() function must be called in the open() and
+ * The v4l2_pipeline_pm_{get, put}() functions must be called in the open() and
  * close() handlers of video device nodes. It increments or decrements the use
  * count of all subdev entities in the pipeline.
  *
@@ -423,7 +423,7 @@ static int pipeline_pm_power(struct media_entity *entity, int change,
 	return ret;
 }
 
-int v4l2_pipeline_pm_use(struct media_entity *entity, int use)
+static int v4l2_pipeline_pm_use(struct media_entity *entity, unsigned int use)
 {
 	struct media_device *mdev = entity->graph_obj.mdev;
 	int change = use ? 1 : -1;
@@ -444,7 +444,19 @@ int v4l2_pipeline_pm_use(struct media_entity *entity, int use)
 
 	return ret;
 }
-EXPORT_SYMBOL_GPL(v4l2_pipeline_pm_use);
+
+int v4l2_pipeline_pm_get(struct media_entity *entity)
+{
+	return v4l2_pipeline_pm_use(entity, 1);
+}
+EXPORT_SYMBOL_GPL(v4l2_pipeline_pm_get);
+
+void v4l2_pipeline_pm_put(struct media_entity *entity)
+{
+	/* Powering off entities shouldn't fail. */
+	WARN_ON(v4l2_pipeline_pm_use(entity, 0));
+}
+EXPORT_SYMBOL_GPL(v4l2_pipeline_pm_put);
 
 int v4l2_pipeline_link_notify(struct media_link *link, u32 flags,
 			      unsigned int notification)