Re: [PATCH v13 09/16] media: uapi: Define audio sample format fourcc type

[Shengjiu Wang <shengjiu.wang@gmail.com>]

On Fri, Mar 8, 2024 at 3:34 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>
> Hi Shengjiu,
>
> After thinking it over I think this patch can be improved:
>
> On 26/02/2024 9:28 am, Shengjiu Wang wrote:
> > The audio sample format definition is from alsa,
> > the header file is include/uapi/sound/asound.h, but
> > don't include this header file directly, because in
> > user space, there is another copy in alsa-lib.
> > There will be conflict in userspace for include
> > videodev2.h & asound.h and asoundlib.h
> >
> > Here still use the fourcc format.
> >
> > Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
> > ---
> >  .../userspace-api/media/v4l/pixfmt-audio.rst  | 87 +++++++++++++++++++
> >  .../userspace-api/media/v4l/pixfmt.rst        |  1 +
> >  drivers/media/v4l2-core/v4l2-ioctl.c          | 13 +++
> >  include/uapi/linux/videodev2.h                | 23 +++++
> >  4 files changed, 124 insertions(+)
> >  create mode 100644 Documentation/userspace-api/media/v4l/pixfmt-audio.rst
> >
> > diff --git a/Documentation/userspace-api/media/v4l/pixfmt-audio.rst b/Documentation/userspace-api/media/v4l/pixfmt-audio.rst
> > new file mode 100644
> > index 000000000000..04b4a7fbd8f4
> > --- /dev/null
> > +++ b/Documentation/userspace-api/media/v4l/pixfmt-audio.rst
> > @@ -0,0 +1,87 @@
> > +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> > +
> > +.. _pixfmt-audio:
> > +
> > +*************
> > +Audio Formats
> > +*************
> > +
> > +These formats are used for :ref:`audiomem2mem` interface only.
>
> Here you should also document that all these fourccs start with 'AU' and are
> reserved for mappings of the snd_pcm_format_t type.
>
> Also document the v4l2_fourcc_to_audfmt define and the v4l2_audfmt_to_fourcc
> define (see also below).

How about below description?
'
All these fourccs starting with 'AU' are reserved for mappings
of the snd_pcm_format_t type.

The v4l2_audfmt_to_fourcc() is defined to convert snd_pcm_format_t
type to fourcc. The first character is 'A', the second character
is 'U', the third character is ten's digit of snd_pcm_format_t,
the fourth character is unit's digit of snd_pcm_format_t.

The v4l2_fourcc_to_audfmt() is defined to convert these fourccs to
snd_pcm_format_t type.
'
Best regards
Shengjiu Wang
>
> > +
> > +.. tabularcolumns:: |p{5.8cm}|p{1.2cm}|p{10.3cm}|
> > +
> > +.. cssclass:: longtable
> > +
> > +.. flat-table:: Audio Format
> > +    :header-rows:  1
> > +    :stub-columns: 0
> > +    :widths:       3 1 4
> > +
> > +    * - Identifier
> > +      - Code
> > +      - Details
> > +    * .. _V4L2-AUDIO-FMT-S8:
> > +
> > +      - ``V4L2_AUDIO_FMT_S8``
> > +      - 'S8'
> > +      - Corresponds to SNDRV_PCM_FORMAT_S8 in ALSA
> > +    * .. _V4L2-AUDIO-FMT-S16-LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_S16_LE``
> > +      - 'S16_LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_S16_LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-U16-LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_U16_LE``
> > +      - 'U16_LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_U16_LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-S24-LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_S24_LE``
> > +      - 'S24_LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_S24_LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-U24-LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_U24_LE``
> > +      - 'U24_LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_U24_LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-S32-LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_S32_LE``
> > +      - 'S32_LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_S32_LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-U32-LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_U32_LE``
> > +      - 'U32_LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_U32_LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-FLOAT-LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_FLOAT_LE``
> > +      - 'FLOAT_LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_FLOAT_LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-IEC958-SUBFRAME-LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_IEC958_SUBFRAME_LE``
> > +      - 'IEC958_SUBFRAME_LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_IEC958_SUBFRAME_LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-S24-3LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_S24_3LE``
> > +      - 'S24_3LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_S24_3LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-U24-3LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_U24_3LE``
> > +      - 'U24_3LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_U24_3LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-S20-3LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_S20_3LE``
> > +      - 'S20_3LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_S24_3LE in ALSA
> > +    * .. _V4L2-AUDIO-FMT-U20-3LE:
> > +
> > +      - ``V4L2_AUDIO_FMT_U20_3LE``
> > +      - 'U20_3LE'
> > +      - Corresponds to SNDRV_PCM_FORMAT_U20_3LE in ALSA
> > diff --git a/Documentation/userspace-api/media/v4l/pixfmt.rst b/Documentation/userspace-api/media/v4l/pixfmt.rst
> > index 11dab4a90630..2eb6fdd3b43d 100644
> > --- a/Documentation/userspace-api/media/v4l/pixfmt.rst
> > +++ b/Documentation/userspace-api/media/v4l/pixfmt.rst
> > @@ -36,3 +36,4 @@ see also :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`.)
> >      colorspaces
> >      colorspaces-defs
> >      colorspaces-details
> > +    pixfmt-audio
> > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> > index 961abcdf7290..be229c69e991 100644
> > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > @@ -1471,6 +1471,19 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
> >       case V4L2_PIX_FMT_Y210:         descr = "10-bit YUYV Packed"; break;
> >       case V4L2_PIX_FMT_Y212:         descr = "12-bit YUYV Packed"; break;
> >       case V4L2_PIX_FMT_Y216:         descr = "16-bit YUYV Packed"; break;
> > +     case V4L2_AUDIO_FMT_S8:         descr = "8-bit Signed"; break;
> > +     case V4L2_AUDIO_FMT_S16_LE:     descr = "16-bit Signed LE"; break;
> > +     case V4L2_AUDIO_FMT_U16_LE:             descr = "16-bit Unsigned LE"; break;
> > +     case V4L2_AUDIO_FMT_S24_LE:             descr = "24(32)-bit Signed LE"; break;
> > +     case V4L2_AUDIO_FMT_U24_LE:             descr = "24(32)-bit Unsigned LE"; break;
> > +     case V4L2_AUDIO_FMT_S32_LE:             descr = "32-bit Signed LE"; break;
> > +     case V4L2_AUDIO_FMT_U32_LE:             descr = "32-bit Unsigned LE"; break;
> > +     case V4L2_AUDIO_FMT_FLOAT_LE:           descr = "32-bit Float LE"; break;
> > +     case V4L2_AUDIO_FMT_IEC958_SUBFRAME_LE: descr = "32-bit IEC958 LE"; break;
> > +     case V4L2_AUDIO_FMT_S24_3LE:            descr = "24(24)-bit Signed LE"; break;
> > +     case V4L2_AUDIO_FMT_U24_3LE:            descr = "24(24)-bit Unsigned LE"; break;
> > +     case V4L2_AUDIO_FMT_S20_3LE:            descr = "20(24)-bit Signed LE"; break;
> > +     case V4L2_AUDIO_FMT_U20_3LE:            descr = "20(24)-bit Unsigned LE"; break;
> >
> >       default:
> >               /* Compressed formats */
> > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> > index 2c03d2dfadbe..673a6235a029 100644
> > --- a/include/uapi/linux/videodev2.h
> > +++ b/include/uapi/linux/videodev2.h
> > @@ -843,6 +843,29 @@ struct v4l2_pix_format {
> >  #define V4L2_META_FMT_RK_ISP1_PARAMS v4l2_fourcc('R', 'K', '1', 'P') /* Rockchip ISP1 3A Parameters */
> >  #define V4L2_META_FMT_RK_ISP1_STAT_3A        v4l2_fourcc('R', 'K', '1', 'S') /* Rockchip ISP1 3A Statistics */
> >
> > +/*
> > + * Audio-data formats
> > + * All these audio formats use a fourcc starting with 'AU'
> > + * followed by the SNDRV_PCM_FORMAT_ value from asound.h.
>
> Also document here that fourccs starting with 'AU' are reserved for
> the snd_pcm_format_t to fourcc mappings.
>
> That to avoid that someone adds a 'AUXX' fourcc later.
>
> > + */
> > +#define V4L2_AUDIO_FMT_S8                    v4l2_fourcc('A', 'U', '0', '0')
> > +#define V4L2_AUDIO_FMT_S16_LE                        v4l2_fourcc('A', 'U', '0', '2')
> > +#define V4L2_AUDIO_FMT_U16_LE                        v4l2_fourcc('A', 'U', '0', '4')
> > +#define V4L2_AUDIO_FMT_S24_LE                        v4l2_fourcc('A', 'U', '0', '6')
> > +#define V4L2_AUDIO_FMT_U24_LE                        v4l2_fourcc('A', 'U', '0', '8')
> > +#define V4L2_AUDIO_FMT_S32_LE                        v4l2_fourcc('A', 'U', '1', '0')
> > +#define V4L2_AUDIO_FMT_U32_LE                        v4l2_fourcc('A', 'U', '1', '2')
> > +#define V4L2_AUDIO_FMT_FLOAT_LE                      v4l2_fourcc('A', 'U', '1', '4')
> > +#define V4L2_AUDIO_FMT_IEC958_SUBFRAME_LE    v4l2_fourcc('A', 'U', '1', '8')
> > +#define V4L2_AUDIO_FMT_S24_3LE                       v4l2_fourcc('A', 'U', '3', '2')
> > +#define V4L2_AUDIO_FMT_U24_3LE                       v4l2_fourcc('A', 'U', '3', '4')
> > +#define V4L2_AUDIO_FMT_S20_3LE                       v4l2_fourcc('A', 'U', '3', '6')
> > +#define V4L2_AUDIO_FMT_U20_3LE                       v4l2_fourcc('A', 'U', '3', '8')
> > +
> > +#define v4l2_fourcc_to_audfmt(fourcc)        \
> > +     (__force snd_pcm_format_t)(((((fourcc) >> 16) & 0xff) - '0') * 10  \
> > +                                + ((((fourcc) >> 24) & 0xff) - '0'))
> > +
>
> As I suggested in an earlier reply, add this:
>
> #define v4l2_audfmt_to_fourcc(audfmt) \
>         v4l2_fourcc('A', 'U', '0' + (audfmt) / 10, '0' + (audfmt) % 10)
>
> Even though it is not used in the drivers, since this is a public header used
> by drivers and applications, it makes sense to provide the reverse mapping as well.
>
> Please test it in actual code to make sure there are no compilation warnings.
>
> Regards,
>
>         Hans
>
> >  /* priv field value to indicates that subsequent fields are valid. */
> >  #define V4L2_PIX_FMT_PRIV_MAGIC              0xfeedcafe
> >
>