Re: [RFC v3 1/2] v4l2: add support for colorspace conversion for video capture

[Dafna Hirschfeld <dafna.hirschfeld@collabora.com>]

Hi

On 07.05.20 15:00, Hans Verkuil wrote:
> On 16/04/2020 16:56, Dafna Hirschfeld wrote:
>> From: Philipp Zabel <p.zabel@pengutronix.de>
>>
>> For video capture it is the driver that reports the colorspace,
>> Y'CbCr/HSV encoding, quantization range and transfer function
>> used by the video, and there is no way to request something
>> different, even though many HDTV receivers have some sort of
>> colorspace conversion capabilities.
>>
>> For output video this feature already exists since the application
>> specifies this information for the video format it will send out, and
>> the transmitter will enable any available CSC if a format conversion has
>> to be performed in order to match the capabilities of the sink.
>>
>> For video capture we propose adding new pix_format flag:
>> V4L2_PIX_FMT_FLAG_HAS_CSC. The flag is set by the application,
> 
> That should be V4L2_PIX_FMT_FLAG_REQUEST_CSC, since the application actively
> requests the use of the CSC.
Maybe change to V4L2_PIX_FMT_FLAG_ASK_FOR_CSC so people won't think
it is related to the request API ?
> 
>> the driver will interpret the ycbcr_enc/hsv_enc, and quantization fields
>> as the requested colorspace information and will attempt to
>> do the conversion it supports.
>>
>> Drivers set the flags
>> V4L2_FMT_FLAG_CSC_YCBCR_ENC,
>> V4L2_FMT_FLAG_CSC_HSV_ENC,
>> V4L2_FMT_FLAG_CSC_HSV_QUANTIZATION,
> 
> That last define should be 'V4L2_FMT_FLAG_CSC_QUANTIZATION' without 'HSV_'.
> 
>> in the flags field of the struct v4l2_fmtdesc during enumeration to
>> indicate that they support colorspace conversion for the respective field.
>> Currently the conversion of the fields colorspace, xfer_func is not
>> supported since there are no drivers that support it.
>>
>> The same API is added for the subdevices. With the flag V4L2_MBUS_FRAMEFMT_HAS_CSC
> 
> Should also be REQUEST_CSC.
> 
>> set by the application in the VIDIOC_SUBDEV_S_FMT ioctl and the flags
>> V4L2_SUBDEV_MBUS_CODE_CSC_YCBCR_ENC, V4L2_SUBDEV_MBUS_CODE_CSC_QUANTIZATION
>> set by the driver in the VIDIOC_SUBDEV_ENUM_MBUS_CODE ioctl.
>>
>> For subdevices, new 'flags' fields were added to the structs
>> v4l2_subdev_mbus_code_enum, v4l2_mbus_framefmt which are borrowed from the 'reserved' field
>>
>> Drivers do not have to actually look at the flags: if the flags are not
>> set, then the colorspace, ycbcr_enc and quantization fields are set to
>> the default values by the core, i.e. just pass on the received format
>> without conversion.
>>
>> Signed-off-by: Hans Verkuil <Hans Verkuil@cisco.com>
>> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
>> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
>> ---
>> This is v3 of the RFC suggested originaly by Hans Verkuil:
>>
>>   https://patchwork.linuxtv.org/patch/28847/
>>
>> And then a v2 from Philipp Zabel:
>>
>>   https://patchwork.kernel.org/project/linux-media/list/?series=15483
>>
>> changes in v3:
>> I added the API to subdevices as well and added fixes according to
>> comments from Hans.
>> I also added a usecase for the new API for the rkisp1 driver.
>>
>> changes in v2 (reported by Philipp Zabel):
>>   - convert to rst
>>   - split V4L2_PIX_FMT_FLAG_REQUEST_CSC into four separate flags for
>>     colorspace, ycbcr_enc/hsv_enc, quantization, and xfer_func
>>   - let driver set flags to indicate supported features
>>
>> [1] https://patchwork.linuxtv.org/patch/28847/
>>
>>   .../media/v4l/pixfmt-reserved.rst             |  6 +++
>>   .../media/v4l/pixfmt-v4l2-mplane.rst          | 16 ++-----
>>   .../userspace-api/media/v4l/pixfmt-v4l2.rst   | 36 +++++++++++++---
>>   .../media/v4l/subdev-formats.rst              | 42 +++++++++++++++++--
>>   .../media/v4l/vidioc-enum-fmt.rst             | 18 ++++++++
>>   .../v4l/vidioc-subdev-enum-mbus-code.rst      | 23 ++++++++++
>>   drivers/media/v4l2-core/v4l2-ioctl.c          | 19 ++++++++-
>>   drivers/media/v4l2-core/v4l2-subdev.c         |  7 ++++
>>   include/uapi/linux/v4l2-mediabus.h            |  5 ++-
>>   include/uapi/linux/v4l2-subdev.h              |  5 ++-
>>   include/uapi/linux/videodev2.h                |  4 ++
>>   11 files changed, 158 insertions(+), 23 deletions(-)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst b/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
>> index 59b9e7238f90..fa8dada69f8c 100644
>> --- a/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
>> +++ b/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
> 
> Why on earth did the documentation of these pixel format flags end up in
> pixfmt-reserved.rst?
> 
> Can you make a patch that moves this to pixfmt-v4l2.rst?
> 
>> @@ -280,3 +280,9 @@ please make a proposal on the linux-media mailing list.
>>   	by RGBA values (128, 192, 255, 128), the same pixel described with
>>   	premultiplied colors would be described by RGBA values (64, 96,
>>   	128, 128)
>> +    * - ``V4L2_PIX_FMT_FLAG_HAS_CSC``
>> +      - 0x00000002
>> +      - Set by the application. It is only used for capture and is
>> +	ignored for output streams. If set, then request the driver to do
>> +	colorspace conversion from the received colorspace, only conversions
>> +	of Ycbcr encoding, HSV encoding and quantization are supported.
> 
> I'd replace the part "If set..." with this:
> 
> ----------
> If set, then request the driver to do colorspace conversion from the received
> colorspace to the requested colorspace values. If a colorimetry field
> (``colorspace``, ``xfer_func``, ``ycncr_enc`` or ``quantization``) is set to 0,
> then that colorimetry setting will remain unchanged from what was received.
> So to just change the quantization only the ``quantization`` field shall be set
> to a non-zero value (``V4L2_QUANTIZATION_FULL_RANGE`` or
> ``V4L2_QUANTIZATION_LIM_RANGE``) and all other colorimetry fields shall be set to 0.
> 
> To check which conversions are supported by the hardware for the current pixel
> format, see :ref:`fmtdesc-flags`.
> ----------
> 
> 
>> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-v4l2-mplane.rst b/Documentation/userspace-api/media/v4l/pixfmt-v4l2-mplane.rst
>> index 444b4082684c..66f3365d7b72 100644
>> --- a/Documentation/userspace-api/media/v4l/pixfmt-v4l2-mplane.rst
>> +++ b/Documentation/userspace-api/media/v4l/pixfmt-v4l2-mplane.rst
>> @@ -105,29 +105,21 @@ describing all planes of that format.
>>       * - __u8
>>         - ``ycbcr_enc``
>>         - Y'CbCr encoding, from enum :c:type:`v4l2_ycbcr_encoding`.
>> -        This information supplements the ``colorspace`` and must be set by
>> -	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	See struct :c:type:`v4l2_pix_format`.
>>       * - __u8
>>         - ``hsv_enc``
>>         - HSV encoding, from enum :c:type:`v4l2_hsv_encoding`.
>> -        This information supplements the ``colorspace`` and must be set by
>> -	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	See struct :c:type:`v4l2_pix_format`.
>>       * - }
>>         -
>>       * - __u8
>>         - ``quantization``
>>         - Quantization range, from enum :c:type:`v4l2_quantization`.
>> -        This information supplements the ``colorspace`` and must be set by
>> -	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	See struct :c:type:`v4l2_pix_format`.
>>       * - __u8
>>         - ``xfer_func``
>>         - Transfer function, from enum :c:type:`v4l2_xfer_func`.
>> -        This information supplements the ``colorspace`` and must be set by
>> -	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	See struct :c:type:`v4l2_pix_format`.
>>       * - __u8
>>         - ``reserved[7]``
>>         - Reserved for future extensions. Should be zeroed by drivers and
>> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst b/Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst
>> index 759420a872d6..ce57718cd66b 100644
>> --- a/Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst
>> +++ b/Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst
>> @@ -110,8 +110,8 @@ Single-planar format structure
>>         - ``colorspace``
>>         - Image colorspace, from enum :c:type:`v4l2_colorspace`.
>>           This information supplements the ``pixelformat`` and must be set
>> -	by the driver for capture streams and by the application for
>> -	output streams, see :ref:`colorspaces`.
>> +	by the driver for capture streams and by the application for output
>> +	streams, see :ref:`colorspace`.
> 
> This doesn't appear to change anything.
> 
>>       * - __u32
>>         - ``priv``
>>         - This field indicates whether the remaining fields of the
>> @@ -148,13 +148,31 @@ Single-planar format structure
>>         - Y'CbCr encoding, from enum :c:type:`v4l2_ycbcr_encoding`.
>>           This information supplements the ``colorspace`` and must be set by
>>   	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	streams, see :ref:`colorspaces`. If the application sets the
>> +	flag ``V4L2_PIX_FMT_FLAG_HAS_CSC`` then the application can set
>> +	this field for a capture stream to request a specific Y'CbCr encoding
>> +	for the captured image data. The driver will attempt to do the
>> +	conversion to the specified Y'CbCr encoding or return the encoding it
>> +	will use if it can't do the conversion. This field is ignored for
>> +	non-Y'CbCr pixelformats. The driver indicates that ycbcr_enc conversion
>> +	is supported by setting the flag V4L2_FMT_FLAG_CSC_YCBCR_ENC on the
>> +	on the corresponding struct :c:type:`v4l2_fmtdesc` during enumeration.
> 
> on the on the -> in the
> 
>> +	See :ref:`fmtdesc-flags`
>>       * - __u32
>>         - ``hsv_enc``
>>         - HSV encoding, from enum :c:type:`v4l2_hsv_encoding`.
>>           This information supplements the ``colorspace`` and must be set by
>>   	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	streams, see :ref:`colorspaces`. If the application sets the flag
>> +	``V4L2_PIX_FMT_FLAG_HAS_CSC`` then the application can set this
>> +	field for a capture stream to request a specific HSV encoding for the
>> +	captured image data. The driver will attempt to do the conversion to
>> +	the specified HSV encoding or return the encoding it will use if it
>> +	can't do the conversion. This field is ignored for non-HSV
>> +	pixelformats. The driver indicates that hsv_enc conversion
>> +	is supported by setting the flag V4L2_FMT_FLAG_CSC_HSV_ENC on the
>> +	on the corresponding struct :c:type:`v4l2_fmtdesc` during enumeration.
> 
> Ditto.
> 
>> +	See :ref:`fmtdesc-flags`
>>       * - }
>>         -
>>       * - __u32
>> @@ -162,7 +180,15 @@ Single-planar format structure
>>         - Quantization range, from enum :c:type:`v4l2_quantization`.
>>           This information supplements the ``colorspace`` and must be set by
>>   	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	streams, see :ref:`colorspaces`. If the application sets the flag
>> +	``V4L2_PIX_FMT_FLAG_HAS_CSC`` then the application can set
>> +	this field for a capture stream to request a specific quantization
>> +	range for the captured image data. The driver will attempt to do the
>> +	conversion to the specified quantization range or return the
>> +	quantization it will use if it can't do the conversion.  The driver
>> +	indicates that quantization conversion is supported by setting the flag
>> +	V4L2_FMT_FLAG_CSC_QUANTIZATION on the on the corresponding struct
> 
> Ditto
> 
>> +	:c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`
>>       * - __u32
>>         - ``xfer_func``
>>         - Transfer function, from enum :c:type:`v4l2_xfer_func`.
>> diff --git a/Documentation/userspace-api/media/v4l/subdev-formats.rst b/Documentation/userspace-api/media/v4l/subdev-formats.rst
>> index 9a4d61b0d76f..f1d4ca29a3e8 100644
>> --- a/Documentation/userspace-api/media/v4l/subdev-formats.rst
>> +++ b/Documentation/userspace-api/media/v4l/subdev-formats.rst
>> @@ -49,13 +49,33 @@ Media Bus Formats
>>         - Y'CbCr encoding, from enum :c:type:`v4l2_ycbcr_encoding`.
>>           This information supplements the ``colorspace`` and must be set by
>>   	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	streams, see :ref:`colorspaces`. If the application sets the
>> +	flag ``V4L2_MBUS_FRAMEFMT_HAS_CSC`` the the application can set
>> +	this field for a capture stream to request a specific Y'CbCr encoding
>> +	for the mbus data. The driver will attempt to do the
> 
> mbus -> media bus
> 
>> +	conversion to the specified Y'CbCr encoding or return the encoding it
>> +	will use if it can't do the conversion. This field is ignored for
>> +	non-Y'CbCr pixelformats. The driver indicates that ycbcr_enc conversion
> 
> This is a media bus format, not a pixelformat.
> 
>> +	is supported by setting the flag V4L2_SUBDEV_MBUS_CODE_CSC_YCBCR_ENC on
> 
> on -> in
> 
>> +	the corresponding struct c:type:`v4l2_subdev_mbus_code_enum` during
>> +	enumeration. See :ref:`vidioc-subdev-enum-mbus-code.rst <v4l2-subdev-mbus-code-flags>`
>> +
>>       * - __u16
>>         - ``quantization``
>>         - Quantization range, from enum :c:type:`v4l2_quantization`.
>>           This information supplements the ``colorspace`` and must be set by
>>   	the driver for capture streams and by the application for output
>> -	streams, see :ref:`colorspaces`.
>> +	streams, see :ref:`colorspaces`. If the application sets the
>> +	flag ``V4L2_MBUS_FRAMEFMT_HAS_CSC`` the the application can set
>> +	this field for a capture stream to request a specific quantization
>> +	encoding for the mbus data. The driver will attempt to do the
> 
> mbus -> media bus
> 
>> +	conversion to the specified quantization or return the quantization it
>> +	will use if it can't do the conversion. The driver indicates that
>> +	quantization conversion is supported by setting the flag
>> +	V4L2_SUBDEV_MBUS_CODE_CSC_QUANTIZATION on the corresponding struct
> 
> on -> in
> 
>> +	c:type:`v4l2_subdev_mbus_code_enum` during enumeration.
>> +	See :ref:`vidioc-subdev-enum-mbus-code.rst <v4l2-subdev-mbus-code-flags>`
>> +
>>       * - __u16
>>         - ``xfer_func``
>>         - Transfer function, from enum :c:type:`v4l2_xfer_func`.
>> @@ -63,10 +83,26 @@ Media Bus Formats
>>   	the driver for capture streams and by the application for output
>>   	streams, see :ref:`colorspaces`.
>>       * - __u16
>> -      - ``reserved``\ [11]
>> +      - ``flags``
>> +      - flags see:  :ref:v4l2-mbus-framefmt-flags
> 
> flags see: -> See:
> 
>> +    * - __u16
>> +      - ``reserved``\ [10]
>>         - Reserved for future extensions. Applications and drivers must set
>>   	the array to zero.
>>   
>> +.. _v4l2-mbus-framefmt-flags:
>> +
>> +.. flat-table:: v4l2_mbus_framefmt Flags
>> +    :header-rows:  0
>> +    :stub-columns: 0
>> +    :widths:       3 1 4
>> +
>> +    * - ``V4L2_MBUS_FRAMEFMT_HAS_CSC``
>> +      - 0x0001
>> +      - Set by the application. It is only used for capture and is
>> +	ignored for output streams. If set, then request the subdevice to do
>> +	colorspace conversion from the received colorspace, only conversions
>> +	of Ycbcr encoding, and quantization are supported.
> 
> Replace by a similar text as for V4L2_PIX_FMT_FLAG_HAS_CSC.
> 
>>   
>>   
>>   .. _v4l2-mbus-pixelcode:
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> index 7e3142e11d77..125f074543af 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> @@ -145,6 +145,24 @@ formats in preference order, where preferred formats are returned before
>>   	parameters are detected. This flag can only be used in combination
>>   	with the ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to
>>   	compressed formats only. It is also only applies to stateful codecs.
>> +    * - ``V4L2_FMT_FLAG_CSC_YCBCR_ENC``
>> +      - 0x0010
>> +      - The driver allows the application to try to change the default
>> +	ycbcr encoding. This flag is relevant only for capture devices.
>> +	The application can ask to configure the ycbcr_enc of the capture device
>> +	when calling the :c:func:`VIDIOC_S_FMT` ioctl.
> 
> add: ...ioctl with ``V4L2_FMT_FLAG_REQUEST_CSC`` set. (this should probably be
> a reference to the REQUEST_CSC flag documentation).
> 
>> +    * - ``V4L2_FMT_FLAG_CSC_HSV_ENC``
>> +      - 0x0010
>> +      - The driver allows the application to try to change the default
>> +	hsv encoding. This flag is relevant only for capture devices.
>> +	The application can ask to configure the hsv_enc of the capture device
>> +	when calling the :c:func:`VIDIOC_S_FMT` ioctl.
> 
> Ditto. Also: hsv -> HSV.
> 
>> +    * - ``V4L2_FMT_FLAG_CSC_QUANTIZATION``
>> +      - 0x0020
>> +      - The driver allows the application to try to change the default
>> +	quantization. This flag is relevant only for capture devices.
>> +	The application can ask to configure the quantization of the capture device
>> +	when calling the :c:func:`VIDIOC_S_FMT` ioctl.
> 
> Ditto.
> 
>>   
>>   
>>   Return Value
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
>> index 35b8607203a4..4ad87cb74f57 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-subdev-enum-mbus-code.rst
>> @@ -78,11 +78,34 @@ information about the try formats.
>>         - ``which``
>>         - Media bus format codes to be enumerated, from enum
>>   	:ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
>> +    * - __u32
>> +      - ``flags``
>> +      - see :ref:`v4l2-subdev-mbus-code-flags`
> 
> see -> See
> 
>>       * - __u32
>>         - ``reserved``\ [8]
>>         - Reserved for future extensions. Applications and drivers must set
>>   	the array to zero.
>>   
>> +.. _v4l2-subdev-mbus-code-flags:
>> +
>> +
>> +.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{7.7cm}|
>> +
>> +.. flat-table:: flags in struct v4l2_subdev_mbus_code_enum
>> +    :header-rows:  0
>> +    :stub-columns: 0
>> +    :widths:       1 1 2
>> +
>> +    * - V4L2_SUBDEV_MBUS_CODE_CSC_YCBCR_ENC
>> +      - 0x00000001
>> +      - The driver supports setting the ycbcr encoding by the application
>> +	when calling the VIDIOC_SUBDEV_S_FMT ioctl. see :ref:`v4l2-mbus-format`
> 
> see -> See
> 
>> +	on how to do this.
>> +    * - V4L2_SUBDEV_MBUS_CODE_CSC_QUANTIZATION
>> +      - 0x00000002
>> +      - The driver supports setting the quantization by the application
>> +	when calling the VIDIOC_SUBDEV_S_FMT ioctl. see :ref:`v4l2-mbus-format`
> 
> see -> See
> 
>> +	on how to do this.
>>   
>>   Return Value
>>   ============
>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>> index b2ef8e60ea7d..3c7ffb6b15cb 100644
>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>> @@ -1029,6 +1029,15 @@ static void v4l_sanitize_format(struct v4l2_format *fmt)
>>   		fmt->fmt.pix_mp.num_planes = min_t(u32, fmt->fmt.pix_mp.num_planes,
>>   					       VIDEO_MAX_PLANES);
>>   
>> +	if (fmt->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) {
>> +		if (fmt->fmt.pix_mp.flags & V4L2_PIX_FMT_FLAG_HAS_CSC)
>> +			return;
>> +		fmt->fmt.pix_mp.colorspace = V4L2_COLORSPACE_DEFAULT;
>> +		fmt->fmt.pix_mp.ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
>> +		fmt->fmt.pix_mp.quantization = V4L2_QUANTIZATION_DEFAULT;
>> +		fmt->fmt.pix_mp.xfer_func = V4L2_XFER_FUNC_DEFAULT;
>> +	}
>> +
>>   	/*
>>   	 * The v4l2_pix_format structure has been extended with fields that were
>>   	 * not previously required to be set to zero by applications. The priv
>> @@ -1043,8 +1052,16 @@ static void v4l_sanitize_format(struct v4l2_format *fmt)
>>   	    fmt->type != V4L2_BUF_TYPE_VIDEO_OUTPUT)
>>   		return;
>>   
>> -	if (fmt->fmt.pix.priv == V4L2_PIX_FMT_PRIV_MAGIC)
>> +	if (fmt->fmt.pix.priv == V4L2_PIX_FMT_PRIV_MAGIC) {
>> +		if (fmt->type != V4L2_BUF_TYPE_VIDEO_CAPTURE ||
>> +		    fmt->fmt.pix.flags & V4L2_PIX_FMT_FLAG_HAS_CSC)
>> +			return;
>> +		fmt->fmt.pix.colorspace = V4L2_COLORSPACE_DEFAULT;
>> +		fmt->fmt.pix.ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
>> +		fmt->fmt.pix.quantization = V4L2_QUANTIZATION_DEFAULT;
>> +		fmt->fmt.pix.xfer_func = V4L2_XFER_FUNC_DEFAULT;
>>   		return;
>> +	}
>>   
>>   	fmt->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
>>   
>> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
>> index a376b351135f..51e009936aad 100644
>> --- a/drivers/media/v4l2-core/v4l2-subdev.c
>> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
>> @@ -477,6 +477,13 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
>>   	case VIDIOC_SUBDEV_S_FMT: {
>>   		struct v4l2_subdev_format *format = arg;
>>   
>> +		if (!(format->format.flags & V4L2_MBUS_FRAMEFMT_HAS_CSC)) {
>> +			format->format.colorspace = V4L2_COLORSPACE_DEFAULT;
>> +			format->format.xfer_func = V4L2_XFER_FUNC_DEFAULT;
>> +			format->format.ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
>> +			format->format.quantization = V4L2_QUANTIZATION_DEFAULT;
>> +		}
>> +
>>   		memset(format->reserved, 0, sizeof(format->reserved));
>>   		memset(format->format.reserved, 0, sizeof(format->format.reserved));
>>   		return v4l2_subdev_call(sd, pad, set_fmt, subdev_fh->pad, format);
>> diff --git a/include/uapi/linux/v4l2-mediabus.h b/include/uapi/linux/v4l2-mediabus.h
>> index 123a231001a8..89ff0ad6a631 100644
>> --- a/include/uapi/linux/v4l2-mediabus.h
>> +++ b/include/uapi/linux/v4l2-mediabus.h
>> @@ -16,6 +16,8 @@
>>   #include <linux/types.h>
>>   #include <linux/videodev2.h>
>>   
>> +#define V4L2_MBUS_FRAMEFMT_HAS_CSC	0x0001
>> +
>>   /**
>>    * struct v4l2_mbus_framefmt - frame format on the media bus
>>    * @width:	image width
>> @@ -36,7 +38,8 @@ struct v4l2_mbus_framefmt {
>>   	__u16			ycbcr_enc;
>>   	__u16			quantization;
>>   	__u16			xfer_func;
>> -	__u16			reserved[11];
>> +	__u16			flags;
>> +	__u16			reserved[10];
>>   };
>>   
>>   #ifndef __KERNEL__
>> diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
>> index 03970ce30741..4410b26a7158 100644
>> --- a/include/uapi/linux/v4l2-subdev.h
>> +++ b/include/uapi/linux/v4l2-subdev.h
>> @@ -65,6 +65,8 @@ struct v4l2_subdev_crop {
>>   	__u32 reserved[8];
>>   };
>>   
>> +#define V4L2_SUBDEV_MBUS_CODE_CSC_YCBCR_ENC	0x00000001
> 
> I think it is better to add an HSV_ENC alias here as well.
> 
> It's for readability only, since talking about YCBCR_ENC when the mediabus format
> is a HSV format is just weird.

I see that in 'v4l2_pix_format' the {ycbcr_enc, hsv_enc} are a union
but in 'v4l2_mbus_framefmt' there is only the field ycbcr_enc.
I wonder why is that, since I see there is one HSV media bus format
V4L2_MBUS_FROM_MEDIA_BUS_FMT(AHSV8888_1X32).

So I guess this is why I didn't add a V4L2_SUBDEV_MBUS_CODE_CSC_HSV_ENC define.
I also didn't add this flag to the docs. Should I?

Thanks,
Dafna

> 
>> +#define V4L2_SUBDEV_MBUS_CODE_CSC_QUANTIZATION	0x00000002
>>   /**
>>    * struct v4l2_subdev_mbus_code_enum - Media bus format enumeration
>>    * @pad: pad number, as reported by the media API
>> @@ -77,7 +79,8 @@ struct v4l2_subdev_mbus_code_enum {
>>   	__u32 index;
>>   	__u32 code;
>>   	__u32 which;
>> -	__u32 reserved[8];
>> +	__u32 flags;
>> +	__u32 reserved[7];
>>   };
>>   
>>   /**
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 9817b7e2c968..adc9dd1080b8 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -772,6 +772,7 @@ struct v4l2_pix_format {
>>   
>>   /* Flags */
>>   #define V4L2_PIX_FMT_FLAG_PREMUL_ALPHA	0x00000001
>> +#define V4L2_PIX_FMT_FLAG_HAS_CSC	0x00000002
>>   
>>   /*
>>    *	F O R M A T   E N U M E R A T I O N
>> @@ -789,6 +790,9 @@ struct v4l2_fmtdesc {
>>   #define V4L2_FMT_FLAG_EMULATED			0x0002
>>   #define V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM	0x0004
>>   #define V4L2_FMT_FLAG_DYN_RESOLUTION		0x0008
>> +#define V4L2_FMT_FLAG_CSC_YCBCR_ENC		0x0010
>> +#define V4L2_FMT_FLAG_CSC_HSV_ENC		0x0010
>> +#define V4L2_FMT_FLAG_CSC_QUANTIZATION		0x0020
>>   
>>   	/* Frame Size and frame rate enumeration */
>>   /*
>>
> 
> I think this is quite good, it's mainly doc improvements and renaming HAS_CSC to REQUEST_CSC.
> 
> That said, I do want to see this supported in at least vivid (vimc would be nice
> too!). And v4l2-ctl needs a patch to support this.
> 
> A compliance test for v4l2-compliance would be nice too, but it is not a prerequisite.
> I'm not entirely sure what would be the best way to test this. Perhaps a vivid-specific
> test might be easiest (i.e., don't test it for all drivers, but just for vivid).
> 
> Regards,
> 
> 	Hans
>