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Date: Fri, 8 Mar 2024 15:04:23 +0100
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Subject: Re: [PATCH v13 09/16] media: uapi: Define audio sample format fourcc
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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
References: <1708936109-11587-1-git-send-email-shengjiu.wang@nxp.com>
 <1708936109-11587-10-git-send-email-shengjiu.wang@nxp.com>
 <df05261f-2f0e-490f-883b-72ad8a02d11b@xs4all.nl>
 <CAA+D8AMJOCfp6WdqYqy7KSj=mX9o_D5U-aF6Wn=3cOnhWg7VDg@mail.gmail.com>
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From: Hans Verkuil <hverkuil@xs4all.nl>
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On 08/03/2024 2:52 pm, Shengjiu Wang wrote:
> On Fri, Mar 8, 2024 at 8:06 PM Hans Verkuil <hverkuil@xs4all.nl> wrote:
>>
>> 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.
> 
> I test this definition, the compiler doesn't report warning.

typedef int __bitwise snd_pcm_format_t;

And __bitwise is apparently a sparse static analyzer attribute, so I suspect that the
v4l2_audfmt_to_fourcc definition will cause a sparse warning. So you need to check
with sparse.

Regards,

	Hans

> 
> best regards
> Shengjiu Wang
> 
>>>>
>>>> Regards,
>>>>
>>>>         Hans
>>>>
>>>>>  /* priv field value to indicates that subsequent fields are valid. */
>>>>>  #define V4L2_PIX_FMT_PRIV_MAGIC              0xfeedcafe
>>>>>
>>>>
>>