linux-kernel - Re: [PATCH] v4l: Add source change event for colorimetry

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Message-ID: <d11da037-92e5-2ee7-8723-10162d16eba9@linaro.org>
Date:   Tue, 13 Oct 2020 12:02:59 +0300
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Tomasz Figa <tfiga@...omium.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Nicolas Dufresne <nicolas@...fresne.ca>
Subject: Re: [PATCH] v4l: Add source change event for colorimetry

Hi,

On 7/2/20 2:52 PM, Stanimir Varbanov wrote:
> Hi,
> 
> Once we have this event there is still open question how the client will
> know the data buffer on which the new colorspace is valid/applied.
> 
> The options could be:
>  * a new buffer flag and
>  * some information in the v4l2_event structure.
> 
> Thoughts?

Kindly ping.

> 
> On 7/2/20 1:00 PM, Stanimir Varbanov wrote:
>> This event indicate that the source colorspace is changed
>> during run-time. The client has to retrieve the new colorspace
>> identifiers by getting the format (G_FMT).
>>
>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
>> ---
>>  .../userspace-api/media/v4l/vidioc-dqevent.rst        | 11 ++++++++++-
>>  .../userspace-api/media/videodev2.h.rst.exceptions    |  1 +
>>  include/uapi/linux/videodev2.h                        |  1 +
>>  3 files changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst b/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
>> index a9a176d5256d..3f69c753db58 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
>> @@ -381,7 +381,16 @@ call.
>>  	that many Video Capture devices are not able to recover from a temporary
>>  	loss of signal and so restarting streaming I/O is required in order for
>>  	the hardware to synchronize to the video signal.
>> -
>> +    * - ``V4L2_EVENT_SRC_CH_COLORIMETRY``
>> +      - 0x0002
>> +      - This event gets triggered when a colorspace change is detected at
>> +	an input. By colorspace change here we include also changes in the
>> +	colorspace specifiers (transfer function, Y'CbCr encoding and
>> +	quantization). This event can come from an input or from video decoder.
>> +	Once the event has been send to the client the driver has to update
>> +	the colorspace specifiers internally so that they could be retrieved by
>> +	client. In that case queue re-negotiation is not needed as this change
>> +	only reflects on the interpretation of the data.
>>  
>>  Return Value
>>  ============
>> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> index ca05e4e126b2..54fc21af852d 100644
>> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> @@ -492,6 +492,7 @@ replace define V4L2_EVENT_CTRL_CH_FLAGS ctrl-changes-flags
>>  replace define V4L2_EVENT_CTRL_CH_RANGE ctrl-changes-flags
>>  
>>  replace define V4L2_EVENT_SRC_CH_RESOLUTION src-changes-flags
>> +replace define V4L2_EVENT_SRC_CH_COLORIMETRY src-changes-flags
>>  
>>  replace define V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ :c:type:`v4l2_event_motion_det`
>>  
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 303805438814..b5838bc4e3a3 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -2351,6 +2351,7 @@ struct v4l2_event_frame_sync {
>>  };
>>  
>>  #define V4L2_EVENT_SRC_CH_RESOLUTION		(1 << 0)
>> +#define V4L2_EVENT_SRC_CH_COLORIMETRY		(1 << 1)
>>  
>>  struct v4l2_event_src_change {
>>  	__u32 changes;
>>
> 

-- 
regards,
Stan