On 03/02/2017 03:48 PM, Steve Longerbeam wrote:

On 03/02/2017 08:02 AM, Sakari Ailus wrote:

quoted

Hi Steve,

On Wed, Feb 15, 2017 at 06:19:16PM -0800, Steve Longerbeam wrote:

quoted

v4l2_pipeline_inherit_controls() will add the v4l2 controls from
all subdev entities in a pipeline to a given video device.

Signed-off-by: Steve Longerbeam <redacted>
---
 drivers/media/v4l2-core/v4l2-mc.c | 48
+++++++++++++++++++++++++++++++++++++++
 include/media/v4l2-mc.h           | 25 ++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-mc.c

b/drivers/media/v4l2-core/v4l2-mc.c
index 303980b..09d4d97 100644

--- a/drivers/media/v4l2-core/v4l2-mc.c
+++ b/drivers/media/v4l2-core/v4l2-mc.c

@@ -22,6 +22,7 @@
 #include <linux/usb.h>
 #include <media/media-device.h>
 #include <media/media-entity.h>
+#include <media/v4l2-ctrls.h>
 #include <media/v4l2-fh.h>
 #include <media/v4l2-mc.h>
 #include <media/v4l2-subdev.h>

@@ -238,6 +239,53 @@ int v4l_vb2q_enable_media_source(struct

vb2_queue *q)
 }
 EXPORT_SYMBOL_GPL(v4l_vb2q_enable_media_source);

+int __v4l2_pipeline_inherit_controls(struct video_device *vfd,
+                     struct media_entity *start_entity)

I have a few concerns / questions:

- What's the purpose of this patch? Why not to access the sub-device node
  directly?

I don't really understand what you are trying to say. That's exactly
what this function is doing, accessing every subdevice in a pipeline
directly, in one convenient function call.

quoted

- This implementation is only workable as long as you do not modify the
  pipeline. Once you disable a link along the pipeline, a device where
the
  control was inherited from may no longer be a part of the pipeline.

That's correct. It's up to the media driver to clear the video device's
inherited controls whenever the pipeline is modified, and then call this
function again if need be.

And here is where I need to eat my words :). I'm not actually
clearing the inherited controls if an upstream link from the
device node link is modified after the whole pipeline has been
configured. If the user does that the controls can become
invalid. Need to fix that by clearing device node controls in
the link_notify callback.

Steve

In imx-media driver, the function is called in link_setup when the link
from a source pad that is attached to a capture video node is enabled.
This is the last link that must be made to define the pipeline, so it
is at this time that a complete list of subdevice controls can be
gathered by walking the pipeline.