Re: [RFC v3 2/2] media: staging: rkisp1: allow quantization conversion from userspace for isp source pad

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

On 29.06.20 14:21, Laurent Pinchart wrote:
> Hi Dafna,
> 
> On Mon, Jun 29, 2020 at 02:08:39PM +0200, Dafna Hirschfeld wrote:
>> On 28.06.20 23:37, Laurent Pinchart wrote:
>>> On Sun, Jun 28, 2020 at 11:33:30PM +0200, Tomasz Figa wrote:
>>>> On Sun, Jun 28, 2020 at 10:27 PM Laurent Pinchart wrote:
>>>>> On Sun, Jun 28, 2020 at 04:59:34PM +0200, Tomasz Figa wrote:
>>>>>> On Sun, Jun 28, 2020 at 3:15 PM Laurent Pinchart wrote:
>>>>>>> On Sun, Jun 28, 2020 at 03:10:41PM +0200, Tomasz Figa wrote:
>>>>>>>> On Fri, Jun 26, 2020 at 2:15 AM Helen Koike <helen.koike@collabora.com> wrote:
>>>>>>>>> On 6/18/20 4:25 PM, Tomasz Figa wrote:
>>>>>>>>>> On Thu, Jun 18, 2020 at 08:54:34PM +0200, Dafna Hirschfeld wrote:
>>>>>>>>>>> On 18.06.20 20:49, Tomasz Figa wrote:
>>>>>>>>>>>> On Thu, Jun 18, 2020 at 08:26:33PM +0200, Dafna Hirschfeld wrote:
>>>>>>>>>>>>> On 18.06.20 19:27, Tomasz Figa wrote:
>>>>>>>>>>>>>> On Wed, Jun 10, 2020 at 2:08 PM Tomasz Figa wrote:
>>>>>>>>>>>>>>> On Thu, Jun 4, 2020 at 9:11 PM Dafna Hirschfeld wrote:
>>>>>>>>>>>>>>>> On 04.06.20 19:54, Tomasz Figa wrote:
>>>>>>>>>>>>>>>>> On Thu, Apr 16, 2020 at 04:56:05PM +0200, Dafna Hirschfeld wrote:
>>>>>>>>>>>>>>>>>> The isp entity has a hardware support to force full range quantization
>>>>>>>>>>>>>>>>>> for YUV formats. Use the new API to indicate userspace that
>>>>>>>>>>>>>>>>>> quantization conversion is supported by adding the flag
>>>>>>>>>>>>>>>>>> V4L2_SUBDEV_MBUS_CODE_CSC_QUANTIZATION during media code enumeration.
>>>>>>>>>>>>>>>>>> Then uppon s_fmt on the video source pad, we assign the
>>>>>>>>>>>>>>>>>> quantization from userspace for YUV formats.
>>>>>>>>>>>>>>>>>> Also in the capture and resizer entities we retrieve the colorspace
>>>>>>>>>>>>>>>>>> from the isp entity.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
>>>>>>>>>>>>>>>>>> ---
>>>>>>>>>>>>>>>>>>       drivers/staging/media/rkisp1/rkisp1-capture.c | 28 ++++++-------
>>>>>>>>>>>>>>>>>>       drivers/staging/media/rkisp1/rkisp1-common.h  |  2 +
>>>>>>>>>>>>>>>>>>       drivers/staging/media/rkisp1/rkisp1-isp.c     | 39 +++++++++++++++++--
>>>>>>>>>>>>>>>>>>       drivers/staging/media/rkisp1/rkisp1-resizer.c | 13 +++++++
>>>>>>>>>>>>>>>>>>       4 files changed, 65 insertions(+), 17 deletions(-)
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> diff --git a/drivers/staging/media/rkisp1/rkisp1-capture.c b/drivers/staging/media/rkisp1/rkisp1-capture.c
>>>>>>>>>>>>>>>>>> index fbf62399fe3d..aca0f93bc772 100644
>>>>>>>>>>>>>>>>>> --- a/drivers/staging/media/rkisp1/rkisp1-capture.c
>>>>>>>>>>>>>>>>>> +++ b/drivers/staging/media/rkisp1/rkisp1-capture.c
>>>>>>>>>>>>>>>>>> @@ -1066,14 +1066,13 @@ static void rkisp1_try_fmt(const struct rkisp1_capture *cap,
>>>>>>>>>>>>>>>>>>                             const struct v4l2_format_info **fmt_info)
>>>>>>>>>>>>>>>>>>       {
>>>>>>>>>>>>>>>>>>          const struct rkisp1_capture_config *config = cap->config;
>>>>>>>>>>>>>>>>>> -    struct rkisp1_capture *other_cap =
>>>>>>>>>>>>>>>>>> -                    &cap->rkisp1->capture_devs[cap->id ^ 1];
>>>>>>>>>>>>>>>>>>          const struct rkisp1_capture_fmt_cfg *fmt;
>>>>>>>>>>>>>>>>>>          const struct v4l2_format_info *info;
>>>>>>>>>>>>>>>>>>          const unsigned int max_widths[] = { RKISP1_RSZ_MP_SRC_MAX_WIDTH,
>>>>>>>>>>>>>>>>>>                                              RKISP1_RSZ_SP_SRC_MAX_WIDTH };
>>>>>>>>>>>>>>>>>>          const unsigned int max_heights[] = { RKISP1_RSZ_MP_SRC_MAX_HEIGHT,
>>>>>>>>>>>>>>>>>>                                               RKISP1_RSZ_SP_SRC_MAX_HEIGHT};
>>>>>>>>>>>>>>>>>> +    struct v4l2_subdev_format isp_sd_fmt;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>          fmt = rkisp1_find_fmt_cfg(cap, pixm->pixelformat);
>>>>>>>>>>>>>>>>>>          if (!fmt) {
>>>>>>>>>>>>>>>>>> @@ -1081,24 +1080,27 @@ static void rkisp1_try_fmt(const struct rkisp1_capture *cap,
>>>>>>>>>>>>>>>>>>                  pixm->pixelformat = fmt->fourcc;
>>>>>>>>>>>>>>>>>>          }
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> +    rkisp1_get_isp_src_fmt(cap->rkisp1, &isp_sd_fmt);
>>>>>>>>>>>>>>>>>> +    pixm->field = isp_sd_fmt.format.field;
>>>>>>>>>>>>>>>>>> +    pixm->colorspace = isp_sd_fmt.format.colorspace;
>>>>>>>>>>>>>>>>>> +    pixm->ycbcr_enc = isp_sd_fmt.format.ycbcr_enc;
>>>>>>>>>>>>>>>>>> +    pixm->xfer_func = isp_sd_fmt.format.xfer_func;
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>> +    /*
>>>>>>>>>>>>>>>>>> +     * isp has a feature to set full range quantization for yuv formats.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> How about "select between limited and full range for YUV formats"?
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> +     * so we need to get the format from the isp.
>>>>>>>>>>>>>>>>>> +     */
>>>>>>>>>>>>>>>>>> +    pixm->quantization = isp_sd_fmt.format.quantization;
>>>>>>>>>>>>>>>>>> +    if (!v4l2_is_format_yuv(cap->pix.info))
>>>>>>>>>>>>>>>>>> +            pixm->quantization = V4L2_QUANTIZATION_FULL_RANGE;
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>>          pixm->width = clamp_t(u32, pixm->width,
>>>>>>>>>>>>>>>>>>                                RKISP1_RSZ_SRC_MIN_WIDTH, max_widths[cap->id]);
>>>>>>>>>>>>>>>>>>          pixm->height = clamp_t(u32, pixm->height,
>>>>>>>>>>>>>>>>>>                                 RKISP1_RSZ_SRC_MIN_HEIGHT, max_heights[cap->id]);
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> -    pixm->field = V4L2_FIELD_NONE;
>>>>>>>>>>>>>>>>>> -    pixm->colorspace = V4L2_COLORSPACE_DEFAULT;
>>>>>>>>>>>>>>>>>> -    pixm->ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
>>>>>>>>>>>>>>>>>> -
>>>>>>>>>>>>>>>>>>          info = rkisp1_fill_pixfmt(pixm, cap->id);
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> -    /* can not change quantization when stream-on */
>>>>>>>>>>>>>>>>>> -    if (other_cap->is_streaming)
>>>>>>>>>>>>>>>>>> -            pixm->quantization = other_cap->pix.fmt.quantization;
>>>>>>>>>>>>>>>>>> -    /* output full range by default, take effect in params */
>>>>>>>>>>>>>>>>>> -    else if (!pixm->quantization ||
>>>>>>>>>>>>>>>>>> -             pixm->quantization > V4L2_QUANTIZATION_LIM_RANGE)
>>>>>>>>>>>>>>>>>> -            pixm->quantization = V4L2_QUANTIZATION_FULL_RANGE;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>          if (fmt_cfg)
>>>>>>>>>>>>>>>>>>                  *fmt_cfg = fmt;
>>>>>>>>>>>>>>>>>> diff --git a/drivers/staging/media/rkisp1/rkisp1-common.h b/drivers/staging/media/rkisp1/rkisp1-common.h
>>>>>>>>>>>>>>>>>> index 2d7b7e078636..7a5576fa14c9 100644
>>>>>>>>>>>>>>>>>> --- a/drivers/staging/media/rkisp1/rkisp1-common.h
>>>>>>>>>>>>>>>>>> +++ b/drivers/staging/media/rkisp1/rkisp1-common.h
>>>>>>>>>>>>>>>>>> @@ -300,6 +300,8 @@ int rkisp1_isp_register(struct rkisp1_device *rkisp1,
>>>>>>>>>>>>>>>>>>                          struct v4l2_device *v4l2_dev);
>>>>>>>>>>>>>>>>>>       void rkisp1_isp_unregister(struct rkisp1_device *rkisp1);
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> +int rkisp1_get_isp_src_fmt(struct rkisp1_device *rkisp1,
>>>>>>>>>>>>>>>>>> +                       struct v4l2_subdev_format *sd_fmt);
>>>>>>>>>>>>>>>>>>       const struct rkisp1_isp_mbus_info *rkisp1_isp_mbus_info_get(u32 mbus_code);
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>       irqreturn_t rkisp1_isp_isr(struct rkisp1_device *rkisp1);
>>>>>>>>>>>>>>>>>> diff --git a/drivers/staging/media/rkisp1/rkisp1-isp.c b/drivers/staging/media/rkisp1/rkisp1-isp.c
>>>>>>>>>>>>>>>>>> index dee8e96f3900..6fdf5ed0b6b1 100644
>>>>>>>>>>>>>>>>>> --- a/drivers/staging/media/rkisp1/rkisp1-isp.c
>>>>>>>>>>>>>>>>>> +++ b/drivers/staging/media/rkisp1/rkisp1-isp.c
>>>>>>>>>>>>>>>>>> @@ -613,6 +613,10 @@ static int rkisp1_isp_enum_mbus_code(struct v4l2_subdev *sd,
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>                  if (code->index == pos - 1) {
>>>>>>>>>>>>>>>>>>                          code->code = fmt->mbus_code;
>>>>>>>>>>>>>>>>>> +                    if (fmt->pixel_enc == V4L2_PIXEL_ENC_YUV &&
>>>>>>>>>>>>>>>>>> +                        dir == RKISP1_DIR_SRC)
>>>>>>>>>>>>>>>>>> +                            code->flags =
>>>>>>>>>>>>>>>>>> +                                    V4L2_SUBDEV_MBUS_CODE_CSC_QUANTIZATION;
>>>>>>>>>>>>>>>>>>                          return 0;
>>>>>>>>>>>>>>>>>>                  }
>>>>>>>>>>>>>>>>>>          }
>>>>>>>>>>>>>>>>>> @@ -639,12 +643,21 @@ static int rkisp1_isp_init_config(struct v4l2_subdev *sd,
>>>>>>>>>>>>>>>>>>          sink_crop->height = RKISP1_DEFAULT_HEIGHT;
>>>>>>>>>>>>>>>>>>          sink_crop->left = 0;
>>>>>>>>>>>>>>>>>>          sink_crop->top = 0;
>>>>>>>>>>>>>>>>>> +    sink_fmt->colorspace = V4L2_COLORSPACE_SRGB;
>>>>>>>>>>>>>>>>>> +    sink_fmt->ycbcr_enc = V4L2_MAP_YCBCR_ENC_DEFAULT(sink_fmt->colorspace);
>>>>>>>>>>>>>>>>>> +    sink_fmt->xfer_func = V4L2_MAP_XFER_FUNC_DEFAULT(sink_fmt->colorspace);
>>>>>>>>>>>>>>>>>> +    sink_fmt->quantization = V4L2_QUANTIZATION_FULL_RANGE;
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>          src_fmt = v4l2_subdev_get_try_format(sd, cfg,
>>>>>>>>>>>>>>>>>>                                               RKISP1_ISP_PAD_SOURCE_VIDEO);
>>>>>>>>>>>>>>>>>>          *src_fmt = *sink_fmt;
>>>>>>>>>>>>>>>>>>          src_fmt->code = RKISP1_DEF_SRC_PAD_FMT;
>>>>>>>>>>>>>>>>>> -    src_fmt->quantization = V4L2_QUANTIZATION_FULL_RANGE;
>>>>>>>>>>>>>>>>>> +    src_fmt->colorspace = V4L2_COLORSPACE_SRGB;
>>>>>>>>>>>>>>>>>> +    src_fmt->ycbcr_enc = V4L2_MAP_YCBCR_ENC_DEFAULT(src_fmt->colorspace);
>>>>>>>>>>>>>>>>>> +    src_fmt->xfer_func = V4L2_MAP_XFER_FUNC_DEFAULT(src_fmt->colorspace);
>>>>>>>>>>>>>>>>>> +    src_fmt->quantization = V4L2_QUANTIZATION_LIM_RANGE;
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>          src_crop = v4l2_subdev_get_try_crop(sd, cfg,
>>>>>>>>>>>>>>>>>>                                              RKISP1_ISP_PAD_SOURCE_VIDEO);
>>>>>>>>>>>>>>>>>> @@ -687,10 +700,17 @@ static void rkisp1_isp_set_src_fmt(struct rkisp1_isp *isp,
>>>>>>>>>>>>>>>>>>                  isp->src_fmt = mbus_info;
>>>>>>>>>>>>>>>>>>          src_fmt->width  = src_crop->width;
>>>>>>>>>>>>>>>>>>          src_fmt->height = src_crop->height;
>>>>>>>>>>>>>>>>>> -    src_fmt->quantization = format->quantization;
>>>>>>>>>>>>>>>>>> -    /* full range by default */
>>>>>>>>>>>>>>>>>> -    if (!src_fmt->quantization)
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>> +    src_fmt->colorspace = V4L2_COLORSPACE_SRGB;
>>>>>>>>>>>>>>>>>> +    src_fmt->ycbcr_enc = V4L2_MAP_YCBCR_ENC_DEFAULT(src_fmt->colorspace);
>>>>>>>>>>>>>>>>>> +    src_fmt->xfer_func = V4L2_MAP_XFER_FUNC_DEFAULT(src_fmt->colorspace);
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>> +    if (mbus_info->pixel_enc == V4L2_PIXEL_ENC_BAYER)
>>>>>>>>>>>>>>>>>>                  src_fmt->quantization = V4L2_QUANTIZATION_FULL_RANGE;
>>>>>>>>>>>>>>>>>> +    else if (format->quantization == V4L2_QUANTIZATION_DEFAULT)
>>>>>>>>>>>>>>>>>> +            src_fmt->quantization = V4L2_QUANTIZATION_LIM_RANGE;
>>>>>>>>>>>>>>>>>> +    else
>>>>>>>>>>>>>>>>>> +            src_fmt->quantization = format->quantization;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>          *format = *src_fmt;
>>>>>>>>>>>>>>>>>>       }
>>>>>>>>>>>>>>>>>> @@ -1068,6 +1088,17 @@ int rkisp1_isp_register(struct rkisp1_device *rkisp1,
>>>>>>>>>>>>>>>>>>          return ret;
>>>>>>>>>>>>>>>>>>       }
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> +int rkisp1_get_isp_src_fmt(struct rkisp1_device *rkisp1,
>>>>>>>>>>>>>>>>>> +                       struct v4l2_subdev_format *sd_fmt)
>>>>>>>>>>>>>>>>>> +{
>>>>>>>>>>>>>>>>>> +    struct rkisp1_isp *isp = &rkisp1->isp;
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>> +    sd_fmt->which = V4L2_SUBDEV_FORMAT_ACTIVE;
>>>>>>>>>>>>>>>>>> +    sd_fmt->pad = RKISP1_ISP_PAD_SOURCE_VIDEO;
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>> +    return v4l2_subdev_call(&isp->sd, pad, get_fmt, NULL, sd_fmt);
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Do we need to get through the external API to access data that is
>>>>>>>>>>>>>>>>> driver-internal anyway?
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> +}
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>>       void rkisp1_isp_unregister(struct rkisp1_device *rkisp1)
>>>>>>>>>>>>>>>>>>       {
>>>>>>>>>>>>>>>>>>          struct v4l2_subdev *sd = &rkisp1->isp.sd;
>>>>>>>>>>>>>>>>>> diff --git a/drivers/staging/media/rkisp1/rkisp1-resizer.c b/drivers/staging/media/rkisp1/rkisp1-resizer.c
>>>>>>>>>>>>>>>>>> index 7b6b7ddd4169..8705b133de68 100644
>>>>>>>>>>>>>>>>>> --- a/drivers/staging/media/rkisp1/rkisp1-resizer.c
>>>>>>>>>>>>>>>>>> +++ b/drivers/staging/media/rkisp1/rkisp1-resizer.c
>>>>>>>>>>>>>>>>>> @@ -525,6 +525,7 @@ static void rkisp1_rsz_set_sink_fmt(struct rkisp1_resizer *rsz,
>>>>>>>>>>>>>>>>>>          const struct rkisp1_isp_mbus_info *mbus_info;
>>>>>>>>>>>>>>>>>>          struct v4l2_mbus_framefmt *sink_fmt, *src_fmt;
>>>>>>>>>>>>>>>>>>          struct v4l2_rect *sink_crop;
>>>>>>>>>>>>>>>>>> +    struct v4l2_subdev_format isp_sd_fmt;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>          sink_fmt = rkisp1_rsz_get_pad_fmt(rsz, cfg, RKISP1_RSZ_PAD_SINK, which);
>>>>>>>>>>>>>>>>>>          src_fmt = rkisp1_rsz_get_pad_fmt(rsz, cfg, RKISP1_RSZ_PAD_SRC, which);
>>>>>>>>>>>>>>>>>> @@ -539,8 +540,20 @@ static void rkisp1_rsz_set_sink_fmt(struct rkisp1_resizer *rsz,
>>>>>>>>>>>>>>>>>>          if (which == V4L2_SUBDEV_FORMAT_ACTIVE)
>>>>>>>>>>>>>>>>>>                  rsz->pixel_enc = mbus_info->pixel_enc;
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> +    rkisp1_get_isp_src_fmt(rsz->rkisp1, &isp_sd_fmt);
>>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Is this necessary? My understanding was that in the subdev model, it was
>>>>>>>>>>>>>>>>> the userspace responsibility to propagate any configuration changes through
>>>>>>>>>>>>>>>>> the graph.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Also, doing this only here wouldn't fully maintain the
>>>>>>>>>>>>>>>>> consistency of the state. For example, if one sets the ISP subdev format
>>>>>>>>>>>>>>>>> first, then the resizer subdev and then the ISP subdev again, wouldn't the
>>>>>>>>>>>>>>>>> resizer subdev end up with a wrong format?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> yes, this is indeed a bug, I am preparing v4 now.
>>>>>>>>>>>>>>>> What I thought to do is adding quantization conversion
>>>>>>>>>>>>>>>> support also on ther resizer and capture entities.
>>>>>>>>>>>>>>>> Then in the 'link_validation' callbacks, there
>>>>>>>>>>>>>>>> is a validation that the quantization fields matches.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> My understanding is that, if we have the following topology
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> [ ISP ] -> [ Resizer ] -> [ Video node ]
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> then the ISP source pad would have the csc capability, while resizer
>>>>>>>>>>>>>>> and video node would just accept whatever is configured on their sink
>>>>>>>>>>>>>>> pads (no need for csc capability for that) and propagate that to their
>>>>>>>>>>>>>>> outputs, i.e. resizer source pad and video node CAPTURE format.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Is this what you were going to implement?
>>>>>>>>>>>>> Hi, I sent a v4 where the CSC capability is set on the reiszer and capture as well.
>>>>>>>>>>>>> I can send a v5 implementing it the way you suggest. Currently the doc says that the colorspace fields
>>>>>>>>>>>>> must be set by the driver for capture streams. This implies that userspace can set it
>>>>>>>>>>>>> only if the CSC is supported.
>>>>>>>>>>>>
>>>>>>>>>>>> Why would the userspace have to set it for the capture stream on the
>>>>>>>>>>>> resizer and video nodes? Couldn't the userspace set it to DEFAULT and
>>>>>>>>>>>> then the driver override to whatever it received on the corresponding
>>>>>>>>>>>> sink?
>>>>>>>>>
>>>>>>>>> According to the documentation [1]:
>>>>>>>>>
>>>>>>>>> "the default quantization encoding as defined by the colorspace"
>>>>>>>>>
>>>>>>>>> Then, for instance, the default for V4L2_COLORSPACE_SRGB is limited range [2].
>>>>>>>>>
>>>>>>>>> Unless we change the definition of DEFAULT to let it accept whatever it receives on the corresponding sink.
>>>>>>>>>
>>>>>>>>> Then the way I understand is:
>>>>>>>>>
>>>>>>>>> [sensor]->[isp]->[resizer]->[capture]
>>>>>>>>>
>>>>>>>>> Userspace should set quantization on:
>>>>>>>>> * sensor source pad
>>>>>>>>> * isp sink pad
>>>>>>>>> * resizer sink pad
>>>>>>>>> * capture node
>>>>>>>>>
>>>>>>>>> The remaining source pads would get values propagated from their sink pads.
>>>>>>>>>
>>>>>>>>> [1] https://linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/v4l/colorspaces-defs.html#c.v4l2_quantization
>>>>>>>>> [2] https://linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/v4l/colorspaces-details.html#col-srgb
>>>>>>>>
>>>>>>>> After discussing this offline, we concluded that:
>>>>>>>> - only the source pad of the ISP entity should expose the CSC capability,
>>>>>>>> - the CAPTURE video node should expose only the formats/color spaces
>>>>>>>> compatible with the current setting of the resizer source,
>>>>>>>> - consistency between the resizer source format and CAPTURE format
>>>>>>>> should be implicitly maintained by the driver.
>>>>>>>
>>>>>>> Do you mean it should be validated at streamon time ?
>>>>>>
>>>>>> Nope. Any V4L2 state must be kept valid all the time, as mandated by
>>>>>> the general V4L2 principles. Wrong configuration of the video node
>>>>>> must not be a reason for STREAMON failing.
>>>>>
>>>>> That's a wrong interpretation of V4L2. On a video-node-centric device (a
>>>>> device that doesn't use the subdev userspace API for configuration) this
>>>>> is correct. In a MC-centric device, the video node and its connected
>>>>> subdev are configured separately.
>>>>
>>>> I don't see this documented anywhere in the specification, maybe
>>>> except a mention of EPIPE or ENOLINK being returned from STREAMON, but
>>>> they explicitly refer to pipeline configuration and not a conflict
>>>> between V4L2 and MC state.
>>>
>>> We're suffering from a lack of documentation in this area :-( Niklas has
>>> authored
>>>
>>> commit f645e6256bd1b12523b759fcc610861fb21c24c7
>>> Author: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
>>> Date:   Tue Apr 21 15:57:38 2020 +0200
>>>
>>>       media: v4l2-dev/ioctl: Add V4L2_CAP_IO_MC
>>>
>>> which is a first step, now we need to document the behaviour of all
>>> ioctls properly when the MC and !MC cases differ.
>>>
>>>> The behavior as you're suggesting would be at least confusing for the
>>>> userspace, because it breaks one of the core principles of V4L2 and
>>>> also there is even no facility to allow the userspace handle this kind
>>>> of behavior, e.g. how to know which memory formats are supported for
>>>> given mbus formats of the related sink.
>>>
>>> commit e5b6b07a1b45dd9d19bec1fa1d60750b0fcf2fb0
>>> Author: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>> Date:   Fri Apr 24 15:43:31 2020 +0200
>>>
>>>       media: v4l2: Extend VIDIOC_ENUM_FMT to support MC-centric devices
>>
>> Hi,
>> What if the video device entity wants to support V4L2_CAP_IO_MC and has two
>> pads registered to the media controller?
>> It seems to be undefined in the documentation.
> 
> What kind of video device would that be ?

I don't know, it is more a theoretical question.




> 
>>> Been missing for a long time... I realized that when I started using the
>>> API in a real userspace implementation instead of just writing test
>>> tools or very device-specific code that could hardcode all this
>>> knowledge.
>>>
>>>>>>> In MC-based
>>>>>>> drivers, entities are isolated from each other from a configuration
>>>>>>> point of view, and the validity of the configuration across the whole
>>>>>>> pipeline is checked at streamon time. I don't think CSC parameters
>>>>>>> should be treated differently than formats in this regard.
>>>>>>
>>>>>> Indeed, the ISP entity and the resizer entity are isolated from each
>>>>>> other and they need to be validated separately. However, the resizer
>>>>>> entity is not isolated from the video node, as there is no
>>>>>> configuration exposed for the video node in the MC API. If MC exposed
>>>>>> an explicit format control for the video interface sink pad, then the
>>>>>> resizer would have to be validated separately indeed, but still that
>>>>>> video interface sink pad would be tied to the rest of the
>>>>>> configuration of the video node (e.g. the CAPTURE format).
>>>>>>
>>>>>>>> Below is the rationale for that:
>>>>>>>> - In the MC model, the video node represents the DMA alone (and thus
>>>>>>>> the reason to have the resizer entities at all) and since the
>>>>>>>> colorspace is not a property of the DMA, it doesn't belong there.
>>>>>>>> - Even if we put that aside, both MP and SP can only output the same
>>>>>>>> colorspace, which would create a dependency between the configuration
>>>>>>>> of the two video nodes, which is not something well defined by V4L2.
>>>>>>>> - A video interface in the MC API doesn't expose control over its
>>>>>>>> input format, which means that the relation between the other side of
>>>>>>>> the link (resizer source) and the video node is implicit and needs to
>>>>>>>> be handled internally in the driver.
>>>>>>>> - V4L2, as opposed to MC, requires that the current state is always
>>>>>>>> consistent and valid. In this case it means that an ioctl on the video
>>>>>>>> node must not be able to alter the state in a way that would make it
>>>>>>>> inconsistent with the state of the matching resizer source.
>