linux-kernel - Re: [PATCH v4 13/36] [media] v4l2: add a frame timeout event

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Date:   Thu, 2 Mar 2017 15:07:21 -0800
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Sakari Ailus <sakari.ailus@....fi>
Cc:     robh+dt@...nel.org, mark.rutland@....com, shawnguo@...nel.org,
        kernel@...gutronix.de, fabio.estevam@....com,
        linux@...linux.org.uk, mchehab@...nel.org, hverkuil@...all.nl,
        nick@...anahar.org, markus.heiser@...marIT.de,
        p.zabel@...gutronix.de, laurent.pinchart+renesas@...asonboard.com,
        bparrot@...com, geert@...ux-m68k.org, arnd@...db.de,
        sudipm.mukherjee@...il.com, minghsiu.tsai@...iatek.com,
        tiffany.lin@...iatek.com, jean-christophe.trotin@...com,
        horms+renesas@...ge.net.au, niklas.soderlund+renesas@...natech.se,
        robert.jarzmik@...e.fr, songjun.wu@...rochip.com,
        andrew-ct.chen@...iatek.com, gregkh@...uxfoundation.org,
        shuah@...nel.org, sakari.ailus@...ux.intel.com, pavel@....cz,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH v4 13/36] [media] v4l2: add a frame timeout event



On 03/02/2017 07:53 AM, Sakari Ailus wrote:
> Hi Steve,
>
> On Wed, Feb 15, 2017 at 06:19:15PM -0800, Steve Longerbeam wrote:
>> Add a new FRAME_TIMEOUT event to signal that a video capture or
>> output device has timed out waiting for reception or transmit
>> completion of a video frame.
>>
>> Signed-off-by: Steve Longerbeam <steve_longerbeam@...tor.com>
>> ---
>>  Documentation/media/uapi/v4l/vidioc-dqevent.rst | 5 +++++
>>  Documentation/media/videodev2.h.rst.exceptions  | 1 +
>>  include/uapi/linux/videodev2.h                  | 1 +
>>  3 files changed, 7 insertions(+)
>>
>> diff --git a/Documentation/media/uapi/v4l/vidioc-dqevent.rst b/Documentation/media/uapi/v4l/vidioc-dqevent.rst
>> index 8d663a7..dd77d9b 100644
>> --- a/Documentation/media/uapi/v4l/vidioc-dqevent.rst
>> +++ b/Documentation/media/uapi/v4l/vidioc-dqevent.rst
>> @@ -197,6 +197,11 @@ call.
>>  	the regions changes. This event has a struct
>>  	:c:type:`v4l2_event_motion_det`
>>  	associated with it.
>> +    * - ``V4L2_EVENT_FRAME_TIMEOUT``
>> +      - 7
>> +      - This event is triggered when the video capture or output device
>> +	has timed out waiting for the reception or transmit completion of
>> +	a frame of video.
>
> As you're adding a new interface, I suppose you have an implementation
> around. How do you determine what that timeout should be?

The imx-media driver sets the timeout to 1 second, or 30 frame
periods at 30 fps.

Steve