From mboxrd@z Thu Jan  1 00:00:00 1970
From: slongerbeam@gmail.com (Steve Longerbeam)
Date: Thu, 2 Mar 2017 18:12:43 -0800
Subject: [PATCH v4 14/36] [media] v4l2-mc: add a function to inherit
 controls from a pipeline
In-Reply-To: <141eb012-eb24-7558-2bc5-1fe82f6b7b4b@gmail.com>
References: <1487211578-11360-1-git-send-email-steve_longerbeam@mentor.com>
 <1487211578-11360-15-git-send-email-steve_longerbeam@mentor.com>
 <20170302160257.GK3220@valkosipuli.retiisi.org.uk>
 <141eb012-eb24-7558-2bc5-1fe82f6b7b4b@gmail.com>
Message-ID: <fc8168ef-bf36-b2d9-627b-e4b8c6a5024e@gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org



On 03/02/2017 03:48 PM, Steve Longerbeam wrote:
>
>
> On 03/02/2017 08:02 AM, Sakari Ailus wrote:
>> Hi Steve,
>>
>> On Wed, Feb 15, 2017 at 06:19:16PM -0800, Steve Longerbeam wrote:
>>> 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 <steve_longerbeam@mentor.com>
>>> ---
>>>  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.<snip>
>

Actually I think I understand what you mean now. Yes, the user can
always access a subdev's control directly from its /dev/v4l-subdevXX.
I'm only providing this feature as a convenience to the user, so that
all controls in a pipeline can be accessed from one place, i.e. the
main capture device node.

Steve