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

[Hans Verkuil <hverkuil@xs4all.nl>]

On 08/03/2024 12:52 pm, Shengjiu Wang wrote:
> 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

All these fourccs -> All FourCCs

> of the snd_pcm_format_t type.
> 
> The v4l2_audfmt_to_fourcc() is defined to convert snd_pcm_format_t

convert -> convert the

> type to fourcc. The first character is 'A', the second character

fourcc -> a FourCC

> 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.

"is 'U', and the remaining two characters is the snd_pcm_format_t
value in ASCII. Example: SNDRV_PCM_FORMAT_S16_LE (with value 2)
maps to 'AU02' and SNDRV_PCM_FORMAT_S24_3LE (with value 32) maps
to 'AU32'."

> 
> The v4l2_fourcc_to_audfmt() is defined to convert these fourccs to

fourccs -> FourCCs

> snd_pcm_format_t type.

BTW, given the way snd_pcm_format_t is defined I am fairly certain
some casts are needed for the v4l2_audfmt_to_fourcc define.

Regards,

	Hans

> '
> 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
>>>
>>