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Date:   Wed, 18 Oct 2023 09:31:00 +0200
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Subject: Re: [RFC PATCH v6 09/11] media: uapi: Add audio rate controls support
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To:     Shengjiu Wang <shengjiu.wang@gmail.com>
Cc:     Shengjiu Wang <shengjiu.wang@nxp.com>, sakari.ailus@iki.fi,
        tfiga@chromium.org, m.szyprowski@samsung.com, mchehab@kernel.org,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        Xiubo.Lee@gmail.com, festevam@gmail.com, nicoleotsuka@gmail.com,
        lgirdwood@gmail.com, broonie@kernel.org, perex@perex.cz,
        tiwai@suse.com, alsa-devel@alsa-project.org,
        linuxppc-dev@lists.ozlabs.org
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From:   Hans Verkuil <hverkuil@xs4all.nl>
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On 18/10/2023 09:23, Shengjiu Wang wrote:
> On Wed, Oct 18, 2023 at 10:27 AM Shengjiu Wang <shengjiu.wang@gmail.com> wrote:
>>
>> On Tue, Oct 17, 2023 at 9:37 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>>>
>>> On 17/10/2023 15:11, Shengjiu Wang wrote:
>>>> On Mon, Oct 16, 2023 at 9:16 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>>>>>
>>>>> Hi Shengjiu,
>>>>>
>>>>> On 13/10/2023 10:31, Shengjiu Wang wrote:
>>>>>> Fixed point controls are used by the user to configure
>>>>>> the audio sample rate to driver.
>>>>>>
>>>>>> Add V4L2_CID_ASRC_SOURCE_RATE and V4L2_CID_ASRC_DEST_RATE
>>>>>> new IDs for ASRC rate control.
>>>>>>
>>>>>> Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
>>>>>> ---
>>>>>>  .../userspace-api/media/v4l/common.rst        |  1 +
>>>>>>  .../media/v4l/ext-ctrls-fixed-point.rst       | 36 +++++++++++++++++++
>>>>>>  .../media/v4l/vidioc-g-ext-ctrls.rst          |  4 +++
>>>>>>  .../media/v4l/vidioc-queryctrl.rst            |  7 ++++
>>>>>>  .../media/videodev2.h.rst.exceptions          |  1 +
>>>>>>  drivers/media/v4l2-core/v4l2-ctrls-core.c     |  5 +++
>>>>>>  drivers/media/v4l2-core/v4l2-ctrls-defs.c     |  4 +++
>>>>>>  include/media/v4l2-ctrls.h                    |  2 ++
>>>>>>  include/uapi/linux/v4l2-controls.h            | 13 +++++++
>>>>>>  include/uapi/linux/videodev2.h                |  3 ++
>>>>>>  10 files changed, 76 insertions(+)
>>>>>>  create mode 100644 Documentation/userspace-api/media/v4l/ext-ctrls-fixed-point.rst
>>>>>>
>>>>>> diff --git a/Documentation/userspace-api/media/v4l/common.rst b/Documentation/userspace-api/media/v4l/common.rst
>>>>>> index ea0435182e44..35707edffb13 100644
>>>>>> --- a/Documentation/userspace-api/media/v4l/common.rst
>>>>>> +++ b/Documentation/userspace-api/media/v4l/common.rst
>>>>>> @@ -52,6 +52,7 @@ applicable to all devices.
>>>>>>      ext-ctrls-fm-rx
>>>>>>      ext-ctrls-detect
>>>>>>      ext-ctrls-colorimetry
>>>>>> +    ext-ctrls-fixed-point
>>>>>
>>>>> Rename this to ext-ctrls-audio-m2m.
>>>>>
>>>>>>      fourcc
>>>>>>      format
>>>>>>      planar-apis
>>>>>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-fixed-point.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-fixed-point.rst
>>>>>> new file mode 100644
>>>>>> index 000000000000..2ef6e250580c
>>>>>> --- /dev/null
>>>>>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-fixed-point.rst
>>>>>> @@ -0,0 +1,36 @@
>>>>>> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
>>>>>> +
>>>>>> +.. _fixed-point-controls:
>>>>>> +
>>>>>> +***************************
>>>>>> +Fixed Point Control Reference
>>>>>
>>>>> This is for audio controls. "Fixed Point" is just the type, and it doesn't make
>>>>> sense to group fixed point controls. But it does make sense to group the audio
>>>>> controls.
>>>>>
>>>>> V4L2 controls can be grouped into classes. Basically it is a way to put controls
>>>>> into categories, and for each category there is also a control that gives a
>>>>> description of the class (see 2.15.15 in
>>>>> https://linuxtv.org/downloads/v4l-dvb-apis-new/driver-api/v4l2-controls.html#introduction)
>>>>>
>>>>> If you use e.g. 'v4l2-ctl -l' to list all the controls, then you will see that
>>>>> they are grouped based on what class of control they are.
>>>>>
>>>>> So I think it would be a good idea to create a new control class for M2M audio controls,
>>>>> instead of just adding them to the catch-all 'User Controls' class.
>>>>>
>>>>> Search e.g. for V4L2_CTRL_CLASS_COLORIMETRY and V4L2_CID_COLORIMETRY_CLASS to see how
>>>>> it is done.
>>>>>
>>>>> M2M_AUDIO would probably be a good name for the class.
>>>>>
>>>>>> +***************************
>>>>>> +
>>>>>> +These controls are intended to support an asynchronous sample
>>>>>> +rate converter.
>>>>>
>>>>> Add ' (ASRC).' at the end to indicate the common abbreviation for
>>>>> that.
>>>>>
>>>>>> +
>>>>>> +.. _v4l2-audio-asrc:
>>>>>> +
>>>>>> +``V4L2_CID_ASRC_SOURCE_RATE``
>>>>>> +    sets the resampler source rate.
>>>>>> +
>>>>>> +``V4L2_CID_ASRC_DEST_RATE``
>>>>>> +    sets the resampler destination rate.
>>>>>
>>>>> Document the unit (Hz) for these two controls.
>>>>>
>>>>>> +
>>>>>> +.. c:type:: v4l2_ctrl_fixed_point
>>>>>> +
>>>>>> +.. cssclass:: longtable
>>>>>> +
>>>>>> +.. tabularcolumns:: |p{1.5cm}|p{5.8cm}|p{10.0cm}|
>>>>>> +
>>>>>> +.. flat-table:: struct v4l2_ctrl_fixed_point
>>>>>> +    :header-rows:  0
>>>>>> +    :stub-columns: 0
>>>>>> +    :widths:       1 1 2
>>>>>> +
>>>>>> +    * - __u32
>>>>>
>>>>> Hmm, shouldn't this be __s32?
>>>>>
>>>>>> +      - ``integer``
>>>>>> +      - integer part of fixed point value.
>>>>>> +    * - __s32
>>>>>
>>>>> and this __u32?
>>>>>
>>>>> You want to be able to use this generic type as a signed value.
>>>>>
>>>>>> +      - ``fractional``
>>>>>> +      - fractional part of fixed point value, which is Q31.
>>>>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
>>>>>> index f9f73530a6be..1811dabf5c74 100644
>>>>>> --- a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
>>>>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
>>>>>> @@ -295,6 +295,10 @@ still cause this situation.
>>>>>>        - ``p_av1_film_grain``
>>>>>>        - A pointer to a struct :c:type:`v4l2_ctrl_av1_film_grain`. Valid if this control is
>>>>>>          of type ``V4L2_CTRL_TYPE_AV1_FILM_GRAIN``.
>>>>>> +    * - struct :c:type:`v4l2_ctrl_fixed_point` *
>>>>>> +      - ``p_fixed_point``
>>>>>> +      - A pointer to a struct :c:type:`v4l2_ctrl_fixed_point`. Valid if this control is
>>>>>> +        of type ``V4L2_CTRL_TYPE_FIXED_POINT``.
>>>>>>      * - void *
>>>>>>        - ``ptr``
>>>>>>        - A pointer to a compound type which can be an N-dimensional array
>>>>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
>>>>>> index 4d38acafe8e1..9285f4f39eed 100644
>>>>>> --- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
>>>>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
>>>>>> @@ -549,6 +549,13 @@ See also the examples in :ref:`control`.
>>>>>>        - n/a
>>>>>>        - A struct :c:type:`v4l2_ctrl_av1_film_grain`, containing AV1 Film Grain
>>>>>>          parameters for stateless video decoders.
>>>>>> +    * - ``V4L2_CTRL_TYPE_FIXED_POINT``
>>>>>> +      - n/a
>>>>>> +      - n/a
>>>>>> +      - n/a
>>>>>> +      - A struct :c:type:`v4l2_ctrl_fixed_point`, containing parameter which has
>>>>>> +        integer part and fractional part, i.e. audio sample rate.
>>>>>> +
>>>>>>
>>>>>>  .. raw:: latex
>>>>>>
>>>>>> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>>>> index e61152bb80d1..2faa5a2015eb 100644
>>>>>> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>>>> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>>>> @@ -167,6 +167,7 @@ replace symbol V4L2_CTRL_TYPE_AV1_SEQUENCE :c:type:`v4l2_ctrl_type`
>>>>>>  replace symbol V4L2_CTRL_TYPE_AV1_TILE_GROUP_ENTRY :c:type:`v4l2_ctrl_type`
>>>>>>  replace symbol V4L2_CTRL_TYPE_AV1_FRAME :c:type:`v4l2_ctrl_type`
>>>>>>  replace symbol V4L2_CTRL_TYPE_AV1_FILM_GRAIN :c:type:`v4l2_ctrl_type`
>>>>>> +replace symbol V4L2_CTRL_TYPE_FIXED_POINT :c:type:`v4l2_ctrl_type`
>>>>>>
>>>>>>  # V4L2 capability defines
>>>>>>  replace define V4L2_CAP_VIDEO_CAPTURE device-capabilities
>>>>>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
>>>>>> index a662fb60f73f..7a616ac91059 100644
>>>>>> --- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
>>>>>> +++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
>>>>>> @@ -1168,6 +1168,8 @@ static int std_validate_compound(const struct v4l2_ctrl *ctrl, u32 idx,
>>>>>>               if (!area->width || !area->height)
>>>>>>                       return -EINVAL;
>>>>>>               break;
>>>>>> +     case V4L2_CTRL_TYPE_FIXED_POINT:
>>>>>> +             break;
>>>>>
>>>>> Hmm, this would need this patch 'v4l2-ctrls: add support for V4L2_CTRL_WHICH_MIN/MAX_VAL':
>>>>>
>>>>> https://patchwork.linuxtv.org/project/linux-media/patch/20231010022136.1504015-7-yunkec@google.com/
>>>>>
>>>>> since min and max values are perfectly fine for a fixed point value.
>>>>>
>>>>> Even a step value (currently not supported in that patch) would make sense.
>>>>>
>>>>> But I wonder if we couldn't simplify this: instead of creating a v4l2_ctrl_fixed_point,
>>>>> why not represent the fixed point value as a Q31.32. Then the standard
>>>>> minimum/maximum/step values can be used, and it acts like a regular V4L2_TYPE_INTEGER64.
>>>>>
>>>>> Except that both userspace and drivers need to multiply it with 2^-32 to get the actual
>>>>> value.
>>>>>
>>>>> So in enum v4l2_ctrl_type add:
>>>>>
>>>>>         V4L2_CTRL_TYPE_FIXED_POINT = 10,
>>>>>
>>>>> (10, because it is no longer a compound type).
>>>>
>>>> Seems we don't need V4L2_CTRL_TYPE_FIXED_POINT, just use V4L2_TYPE_INTEGER64?
>>>>
>>>> The reason I use the 'integer' and 'fractional' is that I want
>>>> 'integer' to be the normal sample
>>>> rate, for example 48kHz.  The 'fractional' is the difference with
>>>> normal sample rate.
>>>>
>>>> For example, the rate = 47998.12345.  so integer = 48000,  fractional= -1.87655.
>>>>
>>>> So if we use s64 for rate, then in driver need to convert the rate to
>>>> the closed normal
>>>> sample rate + fractional.
>>>
>>> That wasn't what the documentation said :-)
>>>
>>> So this is really two controls: one for the 'normal sample rate' (whatever 'normal'
>>> means in this context) and the offset to the actual sample rate.
>>>
>>> Presumably the 'normal' sample rate is set once, while the offset changes
>>> regularly.
>>>
>>> But why do you need the 'normal' sample rate? With audio resampling I assume
>>> you resample from one rate to another, so why do you need a third 'normal'
>>> rate?
>>>
>>
>> 'Normal' rate is used to select the prefilter table.
>>
> 
> Currently I think we may define
> V4L2_CID_M2M_AUDIO_SOURCE_RATE
> V4L2_CID_M2M_AUDIO_DEST_RATE

That makes sense.

> V4L2_CID_M2M_AUDIO_ASRC_RATIO_MOD

OK, can you document this control? Just write it down in the reply, I just want
to understand how the integer value you set here is used.

Regards,

	Hans

> 
> All of them can be V4L2_CTRL_TYPE_INTEGER.
> 
> RATIO_MOD was defined in the very beginning version.
> I think it is better to let users calculate this value.
> 
> The reason is:
> if we define the offset for source rate and dest rate in
> driver separately,  when offset of source rate is set,
> driver don't know if it needs to wait or not the dest rate
> offset,  then go to calculate the ratio_mod.
> 
> best regards
> wang shengjiu
> 
>> Best regards
>> Wang Shengjiu
>>
>>> Regards,
>>>
>>>         Hans
>>>
>>>>
>>>> best regards
>>>> wang shengjiu
>>>>
>>>>>
>>>>>>
>>>>>>       default:
>>>>>>               return -EINVAL;
>>>>>> @@ -1868,6 +1870,9 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct v4l2_ctrl_handler *hdl,
>>>>>>       case V4L2_CTRL_TYPE_AREA:
>>>>>>               elem_size = sizeof(struct v4l2_area);
>>>>>>               break;
>>>>>> +     case V4L2_CTRL_TYPE_FIXED_POINT:
>>>>>> +             elem_size = sizeof(struct v4l2_ctrl_fixed_point);
>>>>>> +             break;
>>>>>>       default:
>>>>>>               if (type < V4L2_CTRL_COMPOUND_TYPES)
>>>>>>                       elem_size = sizeof(s32);
>>>>>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
>>>>>> index 8696eb1cdd61..d8f232df6b6a 100644
>>>>>> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
>>>>>> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
>>>>>> @@ -1602,6 +1602,10 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
>>>>>>       case V4L2_CID_COLORIMETRY_HDR10_MASTERING_DISPLAY:
>>>>>>               *type = V4L2_CTRL_TYPE_HDR10_MASTERING_DISPLAY;
>>>>>>               break;
>>>>>> +     case V4L2_CID_ASRC_SOURCE_RATE:
>>>>>> +     case V4L2_CID_ASRC_DEST_RATE:
>>>>>> +             *type = V4L2_CTRL_TYPE_FIXED_POINT;
>>>>>> +             break;
>>>>>>       default:
>>>>>>               *type = V4L2_CTRL_TYPE_INTEGER;
>>>>>>               break;
>>>>>> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
>>>>>> index 59679a42b3e7..645e4cccafc7 100644
>>>>>> --- a/include/media/v4l2-ctrls.h
>>>>>> +++ b/include/media/v4l2-ctrls.h
>>>>>> @@ -56,6 +56,7 @@ struct video_device;
>>>>>>   * @p_av1_tile_group_entry:  Pointer to an AV1 tile group entry structure.
>>>>>>   * @p_av1_frame:             Pointer to an AV1 frame structure.
>>>>>>   * @p_av1_film_grain:                Pointer to an AV1 film grain structure.
>>>>>> + * @p_fixed_point:           Pointer to a struct v4l2_ctrl_fixed_point.
>>>>>>   * @p:                               Pointer to a compound value.
>>>>>>   * @p_const:                 Pointer to a constant compound value.
>>>>>>   */
>>>>>> @@ -89,6 +90,7 @@ union v4l2_ctrl_ptr {
>>>>>>       struct v4l2_ctrl_av1_tile_group_entry *p_av1_tile_group_entry;
>>>>>>       struct v4l2_ctrl_av1_frame *p_av1_frame;
>>>>>>       struct v4l2_ctrl_av1_film_grain *p_av1_film_grain;
>>>>>> +     struct v4l2_ctrl_fixed_point *p_fixed_point;
>>>>>>       void *p;
>>>>>>       const void *p_const;
>>>>>>  };
>>>>>> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
>>>>>> index c3604a0a3e30..91096259e3ea 100644
>>>>>> --- a/include/uapi/linux/v4l2-controls.h
>>>>>> +++ b/include/uapi/linux/v4l2-controls.h
>>>>>> @@ -112,6 +112,8 @@ enum v4l2_colorfx {
>>>>>>
>>>>>>  /* last CID + 1 */
>>>>>>  #define V4L2_CID_LASTP1                         (V4L2_CID_BASE+44)
>>>>>> +#define V4L2_CID_ASRC_SOURCE_RATE            (V4L2_CID_BASE + 45)
>>>>>> +#define V4L2_CID_ASRC_DEST_RATE                      (V4L2_CID_BASE + 46)
>>>>>
>>>>> This patch needs to be split in three parts:
>>>>>
>>>>> 1) Add the new M2M_AUDIO control class,
>>>>> 2) Add the new V4L2_CTRL_TYPE_FIXED_POINT type,
>>>>> 3) Add the new controls.
>>>>>
>>>>> These are all independent changes, so separating them makes it easier to
>>>>> review.
>>>>>
>>>>>>
>>>>>>  /* USER-class private control IDs */
>>>>>>
>>>>>> @@ -3488,4 +3490,15 @@ struct v4l2_ctrl_av1_film_grain {
>>>>>>  #define V4L2_CID_MPEG_MFC51_BASE        V4L2_CID_CODEC_MFC51_BASE
>>>>>>  #endif
>>>>>>
>>>>>> +/**
>>>>>> + * struct v4l2_ctrl_fixed_point - fixed point parameter.
>>>>>> + *
>>>>>> + * @rate_integer: integer part of fixed point value.
>>>>>> + * @rate_fractional: fractional part of fixed point value
>>>>>> + */
>>>>>> +struct v4l2_ctrl_fixed_point {
>>>>>> +     __u32 integer;
>>>>>
>>>>> __s32?
>>>>>
>>>>>> +     __u32 fractional;
>>>>>> +};
>>>>>> +
>>>>>>  #endif
>>>>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>>>>> index 2ac7b989394c..3ef32c09c2fa 100644
>>>>>> --- a/include/uapi/linux/videodev2.h
>>>>>> +++ b/include/uapi/linux/videodev2.h
>>>>>> @@ -1888,6 +1888,7 @@ struct v4l2_ext_control {
>>>>>>               struct v4l2_ctrl_av1_tile_group_entry __user *p_av1_tile_group_entry;
>>>>>>               struct v4l2_ctrl_av1_frame __user *p_av1_frame;
>>>>>>               struct v4l2_ctrl_av1_film_grain __user *p_av1_film_grain;
>>>>>> +             struct v4l2_ctrl_fixed_point __user *p_fixed_point;
>>>>>>               void __user *ptr;
>>>>>>       };
>>>>>>  } __attribute__ ((packed));
>>>>>> @@ -1966,6 +1967,8 @@ enum v4l2_ctrl_type {
>>>>>>       V4L2_CTRL_TYPE_AV1_TILE_GROUP_ENTRY = 0x281,
>>>>>>       V4L2_CTRL_TYPE_AV1_FRAME            = 0x282,
>>>>>>       V4L2_CTRL_TYPE_AV1_FILM_GRAIN       = 0x283,
>>>>>> +
>>>>>> +     V4L2_CTRL_TYPE_FIXED_POINT          = 0x290,
>>>>>>  };
>>>>>>
>>>>>>  /*  Used in the VIDIOC_QUERYCTRL ioctl for querying controls */
>>>>>
>>>>> Regards,
>>>>>
>>>>>         Hans
>>>