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

[Hans Verkuil <hverkuil@xs4all.nl>]

On 26/05/2020 14:36, Dafna Hirschfeld wrote:
> 
> 
> On 25.05.20 16:25, Hans Verkuil wrote:
>> On 25/05/2020 15:56, Dafna Hirschfeld wrote:
>>> 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 ?
>>
>> How about _SET_CSC? I think that's even better than REQUEST_CSC.
>>
>>>>
>>>>> 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;
>>>>> +		}
> I wonder if those 3 code chunks added to v4l2-ioctl.c and v4l2-subdev.c are actually
> needed. They set the colorspace fields on capture devices to 0 if the HAS_CSC flag is not set.
> But I don't see the reason to do it, if the capture driver do not support CSC it will just ignore
> the values of those fields that came from userspace which is what is already done.
> Also, it could be that a driver does not support CSC and userspace set the SET_CSC flag anyway, in this
> case those fields will not be set to defalut although they should.
> What do you think?

I agree. That code doesn't make sense.

I think it is safe to drop this.

Regards,

	Hans

> 
> Thanks,
> Dafna
> 
>>>>> +
>>>>>    		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?
>>
>> I think this can be done in a separate (final) patch where a union is added for
>> v4l2_mbus_framefmt together with a V4L2_SUBDEV_MBUS_CODE_CSC_HSV_ENC define.
>>
>> These are effectively aliases to make code that works with HSV easier to read,
>> so they do not change functionality.
>>
>> Regards,
>>
>> 	Hans
>>
>>>
>>> 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
>>>>
>>