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From:   Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Date:   Wed, 6 Jul 2022 15:39:41 -0300
Message-ID: <CAAEAJfDNHSBtJD_chSV0_UMTJWztyPFxjORRn0+dSrtcZCoYwg@mail.gmail.com>
Subject: Re: Re: [PATCH v10 11/17] media: uapi: Add V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS
 control
To:     =?UTF-8?Q?Jernej_=C5=A0krabec?= <jernej.skrabec@gmail.com>
Cc:     Benjamin Gaignard <benjamin.gaignard@collabora.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Hans Verkuil <hverkuil@xs4all.nl>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Greg KH <gregkh@linuxfoundation.org>,
        Maxime Ripard <mripard@kernel.org>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Samuel Holland <samuel@sholland.org>,
        Nicolas Dufresne <nicolas.dufresne@collabora.com>,
        Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
        linux-media <linux-media@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
        "open list:STAGING SUBSYSTEM" <linux-staging@lists.linux.dev>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-sunxi@lists.linux.dev,
        Collabora Kernel ML <kernel@collabora.com>
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Hi Jernej,

On Tue, Jul 5, 2022 at 1:11 PM Jernej =C5=A0krabec <jernej.skrabec@gmail.co=
m> wrote:
>
> Dne torek, 05. julij 2022 ob 18:03:28 CEST je Benjamin Gaignard napisal(a=
):
> > Le 05/07/2022 =C3=A0 17:45, Ezequiel Garcia a =C3=A9crit :
> > > Hi guys,
> > >
> > > On Tue, Jul 05, 2022 at 10:54:14AM +0200, Benjamin Gaignard wrote:
> > >> The number of 'entry point offset' can be very variable.
> > >> Instead of using a large static array define a v4l2 dynamic array
> > >> of U32 (V4L2_CTRL_TYPE_U32).
> > >> The number of entry point offsets is reported by the elems field
> > >> and in struct v4l2_ctrl_hevc_slice_params.num_entry_point_offsets
> > >> field.
> > >>
> > >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> > >> Acked-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
> > >> Tested-by: Jernej Skrabec <jernej.skrabec@gmail.com>
> > >> ---
> > >>
> > >>   .../userspace-api/media/v4l/ext-ctrls-codec.rst       | 11 +++++++=
++++
> > >>   drivers/media/v4l2-core/v4l2-ctrls-defs.c             |  5 +++++
> > >>   include/media/hevc-ctrls.h                            |  5 ++++-
> > >>   3 files changed, 20 insertions(+), 1 deletion(-)
> > >>
> > >> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.r=
st
> > >> b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst index
> > >> db0df7d9f27c..8df8d7fdfe70 100644
> > >> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > >> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > >> @@ -3010,6 +3010,9 @@ enum v4l2_mpeg_video_hevc_size_of_length_field=
 -
> > >>
> > >>       * - __u32
> > >>
> > >>         - ``data_bit_offset``
> > >>         - Offset (in bits) to the video data in the current slice da=
ta.
> > >>
> > >> +    * - __u32
> > >> +      - ``num_entry_point_offsets``
> > >> +      - Specifies the number of entry point offset syntax elements =
in
> > >> the slice header.>
> > > This looks underdocumented. Somewhere in the docs it should be mentio=
ned
> > > that the field 'num_entry_point_offsets' is linked to the control
> > > V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS.
> >
> > This field is here because some drivers would like know the number of
> > entry point offsets without getting the entry point offsets data itself=
.
>
> Yeah, this field must be set even when entry points offset control isn't =
used.
> Additionally, if entry point offsets control is needed and if submitting
> multiple slices at once, length of entry point offsets array must be sum =
of
> num_entry_point_offsets of all slices in that job. Not sure where to put =
this
> explanation.
>

This confused me a bit: so you mean that this field (called
num_entry_point_offsets)
must be the sum of "num_entry_point_offsets" syntax elements for
slices in the request?

If this is the case, then perhaps it will be a mistake to name our V4L2 fie=
ld
exactly like the syntax element, since it this sum meaning.
Otherwise, developers would tend to get confused by it.

What do you think?

Thanks,
Ezequiel

> Best regards,
> Jernej
>
> >
> > Benjamin
> >
> > > Thanks,
> > > Ezequiel
> > >
> > >>       * - __u8
> > >>
> > >>         - ``nal_unit_type``
> > >>         - Specifies the coding type of the slice (B, P or I).
> > >>
> > >> @@ -3150,6 +3153,14 @@ enum v4l2_mpeg_video_hevc_size_of_length_fiel=
d -
> > >>
> > >>       \normalsize
> > >>
> > >> +``V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS (integer)``
> > >> +    Specifies entry point offsets in bytes.
> > >> +    This control is a dynamically sized array. The number of entry =
point
> > >> +    offsets is reported by the ``elems`` field.
> > >> +    This bitstream parameter is defined according to :ref:`hevc`.
> > >> +    They are described in section 7.4.7.1 "General slice segment he=
ader
> > >> +    semantics" of the specification.
> > >> +
> > >>
> > >>   ``V4L2_CID_STATELESS_HEVC_SCALING_MATRIX (struct)``
> > >>
> > >>       Specifies the HEVC scaling matrix parameters used for the scal=
ing
> > >>       process
> > >>       for transform coefficients.
> > >>
> > >> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> > >> b/drivers/media/v4l2-core/v4l2-ctrls-defs.c index
> > >> d594efbcbb93..e22921e7ea61 100644
> > >> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> > >> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> > >> @@ -1188,6 +1188,7 @@ const char *v4l2_ctrl_get_name(u32 id)
> > >>
> > >>    case V4L2_CID_STATELESS_HEVC_DECODE_PARAMS:             return
> "HEVC Decode
> > >>    Parameters"; case V4L2_CID_STATELESS_HEVC_DECODE_MODE:
> return "HEVC
> > >>    Decode Mode"; case V4L2_CID_STATELESS_HEVC_START_CODE:
> return "HEVC
> > >>    Start Code";>>
> > >> +  case V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS:       return
> "HEVC Entry
> > >> Point Offsets";>>
> > >>    /* Colorimetry controls */
> > >>    /* Keep the order of the 'case's the same as in v4l2-controls.h!
> */
> > >>
> > >> @@ -1518,6 +1519,10 @@ void v4l2_ctrl_fill(u32 id, const char **name=
,
> > >> enum v4l2_ctrl_type *type,>>
> > >>    case V4L2_CID_STATELESS_HEVC_DECODE_PARAMS:
> > >>            *type =3D V4L2_CTRL_TYPE_HEVC_DECODE_PARAMS;
> > >>            break;
> > >>
> > >> +  case V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS:
> > >> +          *type =3D V4L2_CTRL_TYPE_U32;
> > >> +          *flags |=3D V4L2_CTRL_FLAG_DYNAMIC_ARRAY;
> > >> +          break;
> > >>
> > >>    case V4L2_CID_STATELESS_VP9_COMPRESSED_HDR:
> > >>            *type =3D V4L2_CTRL_TYPE_VP9_COMPRESSED_HDR;
> > >>            break;
> > >>
> > >> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
> > >> index a372c184689e..3a6601a46ced 100644
> > >> --- a/include/media/hevc-ctrls.h
> > >> +++ b/include/media/hevc-ctrls.h
> > >> @@ -20,6 +20,7 @@
> > >>
> > >>   #define V4L2_CID_STATELESS_HEVC_DECODE_PARAMS
> (V4L2_CID_CODEC_BASE +
> > >>   1012)
> > >>   #define V4L2_CID_STATELESS_HEVC_DECODE_MODE      (V4L2_CID_CODEC_B=
ASE
> +
> > >>   1015)
> > >>   #define V4L2_CID_STATELESS_HEVC_START_CODE       (V4L2_CID_CODEC_B=
ASE + 1016)
> > >>
> > >> +#define V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS (V4L2_CID_CODEC=
_BASE
> > >> + 1017)>>
> > >>   /* enum v4l2_ctrl_type type values */
> > >>   #define V4L2_CTRL_TYPE_HEVC_SPS 0x0120
> > >>
> > >> @@ -316,6 +317,8 @@ struct v4l2_hevc_pred_weight_table {
> > >>
> > >>    *
> > >>    * @bit_size: size (in bits) of the current slice data
> > >>    * @data_bit_offset: offset (in bits) to the video data in the cur=
rent
> > >>    slice data>>
> > >> + * @num_entry_point_offsets: specifies the number of entry point of=
fset
> > >> syntax + *                      elements in the slice
> header.
> > >>
> > >>    * @nal_unit_type: specifies the coding type of the slice (B, P or=
 I)
> > >>    * @nuh_temporal_id_plus1: minus 1 specifies a temporal identifier=
 for
> > >>    the NAL unit * @slice_type: see V4L2_HEVC_SLICE_TYPE_{}
> > >>
> > >> @@ -358,7 +361,7 @@ struct v4l2_hevc_pred_weight_table {
> > >>
> > >>   struct v4l2_ctrl_hevc_slice_params {
> > >>
> > >>    __u32   bit_size;
> > >>    __u32   data_bit_offset;
> > >>
> > >> -
> > >> +  __u32   num_entry_point_offsets;
> > >>
> > >>    /* ISO/IEC 23008-2, ITU-T Rec. H.265: NAL unit header */
> > >>    __u8    nal_unit_type;
> > >>    __u8    nuh_temporal_id_plus1;
> > >>
> > >> --
> > >> 2.32.0
>
>