Re: [RFC PATCH v6 09/11] media: uapi: Add audio rate controls support
From: Shengjiu Wang
Date: Tue Oct 17 2023 - 09:11:47 EST
On Mon, Oct 16, 2023 at 9:16 PM Hans Verkuil <hverkuil@xxxxxxxxx> 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@xxxxxxx>
> > ---
> > .../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@xxxxxxxxxx/
>
> 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.
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