Re: [PATCH v12 07/15] media: v4l2: Add audio capture and output support

[Hans Verkuil <hverkuil@xs4all.nl>]

On 17/02/2024 10:42, Mauro Carvalho Chehab wrote:
> Em Thu, 18 Jan 2024 20:32:00 +0800
> Shengjiu Wang <shengjiu.wang@nxp.com> escreveu:
> 
>> Audio signal processing has the requirement for memory to
>> memory similar as Video.
>>
>> This patch is to add this support in v4l2 framework, defined
>> new buffer type V4L2_BUF_TYPE_AUDIO_CAPTURE and
>> V4L2_BUF_TYPE_AUDIO_OUTPUT, defined new format v4l2_audio_format
>> for audio case usage.
>>
>> The created audio device is named "/dev/v4l-audioX".
>>
>> Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
>> ---
>>  .../userspace-api/media/v4l/buffer.rst        |  6 ++
>>  .../media/v4l/dev-audio-mem2mem.rst           | 71 +++++++++++++++++++
>>  .../userspace-api/media/v4l/devices.rst       |  1 +
>>  .../media/v4l/vidioc-enum-fmt.rst             |  2 +
>>  .../userspace-api/media/v4l/vidioc-g-fmt.rst  |  4 ++
>>  .../media/videodev2.h.rst.exceptions          |  2 +
>>  .../media/common/videobuf2/videobuf2-v4l2.c   |  4 ++
>>  drivers/media/v4l2-core/v4l2-compat-ioctl32.c |  9 +++
>>  drivers/media/v4l2-core/v4l2-dev.c            | 17 +++++
>>  drivers/media/v4l2-core/v4l2-ioctl.c          | 53 ++++++++++++++
>>  include/media/v4l2-dev.h                      |  2 +
>>  include/media/v4l2-ioctl.h                    | 34 +++++++++
>>  include/uapi/linux/videodev2.h                | 17 +++++
>>  13 files changed, 222 insertions(+)
>>  create mode 100644 Documentation/userspace-api/media/v4l/dev-audio-mem2mem.rst
>>
>> diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst
>> index 52bbee81c080..a3754ca6f0d6 100644
>> --- a/Documentation/userspace-api/media/v4l/buffer.rst
>> +++ b/Documentation/userspace-api/media/v4l/buffer.rst
>> @@ -438,6 +438,12 @@ enum v4l2_buf_type
>>      * - ``V4L2_BUF_TYPE_META_OUTPUT``
>>        - 14
> 
>>        - Buffer for metadata output, see :ref:`metadata`.
>> +    * - ``V4L2_BUF_TYPE_AUDIO_CAPTURE``
>> +      - 15
>> +      - Buffer for audio capture, see :ref:`audio`.
>> +    * - ``V4L2_BUF_TYPE_AUDIO_OUTPUT``
>> +      - 16
> 
> Hmm... alsa APi define input/output as:
> 	enum {
> 	        SNDRV_PCM_STREAM_PLAYBACK = 0,
> 	        SNDRV_PCM_STREAM_CAPTURE,
> 	        SNDRV_PCM_STREAM_LAST = SNDRV_PCM_STREAM_CAPTURE,
> 	};
> 
> 
> I would use a namespace as close as possible to the
> ALSA API. Also, we're not talking about V4L2, but, instead
> audio. so, not sure if I like the prefix to start with
> V4L2_. Maybe ALSA_?
> 
> So, a better namespace would be:
> 
> 	${prefix}_BUF_TYPE_PCM_STREAM_PLAYBACK
> and
> 	${prefix}_BUF_TYPE_PCM_STREAM_CAPTURE
> 
>> +      - Buffer for audio output, see :ref:`audio`.
>>  
>>  
>>  .. _buffer-flags:
>> diff --git a/Documentation/userspace-api/media/v4l/dev-audio-mem2mem.rst b/Documentation/userspace-api/media/v4l/dev-audio-mem2mem.rst
>> new file mode 100644
>> index 000000000000..68faecfe3a02
>> --- /dev/null
>> +++ b/Documentation/userspace-api/media/v4l/dev-audio-mem2mem.rst
>> @@ -0,0 +1,71 @@
>> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
>> +
>> +.. _audiomem2mem:
>> +
>> +********************************
>> +Audio Memory-To-Memory Interface
>> +********************************
>> +
>> +An audio memory-to-memory device can compress, decompress, transform, or
>> +otherwise convert audio data from one format into another format, in memory.
>> +Such memory-to-memory devices set the ``V4L2_CAP_AUDIO_M2M`` capability.
>> +Examples of memory-to-memory devices are audio codecs, audio preprocessing,
>> +audio postprocessing.
>> +
>> +A memory-to-memory audio node supports both output (sending audio frames from
>> +memory to the hardware) and capture (receiving the processed audio frames
>> +from the hardware into memory) stream I/O. An application will have to
>> +setup the stream I/O for both sides and finally call
>> +:ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` for both capture and output to
>> +start the hardware.
>> +
>> +Memory-to-memory devices function as a shared resource: you can
>> +open the audio node multiple times, each application setting up their
>> +own properties that are local to the file handle, and each can use
>> +it independently from the others. The driver will arbitrate access to
>> +the hardware and reprogram it whenever another file handler gets access.
>> +
>> +Audio memory-to-memory devices are accessed through character device
>> +special files named ``/dev/v4l-audio``
>> +
>> +Querying Capabilities
>> +=====================
>> +
>> +Device nodes supporting the audio memory-to-memory interface set the
>> +``V4L2_CAP_AUDIO_M2M`` flag in the ``device_caps`` field of the
>> +:c:type:`v4l2_capability` structure returned by the :c:func:`VIDIOC_QUERYCAP`
>> +ioctl.
>> +
>> +Data Format Negotiation
>> +=======================
>> +
>> +The audio device uses the :ref:`format` ioctls to select the capture format.
>> +The audio buffer content format is bound to that selected format. In addition
>> +to the basic :ref:`format` ioctls, the :c:func:`VIDIOC_ENUM_FMT` ioctl must be
>> +supported as well.
>> +
>> +To use the :ref:`format` ioctls applications set the ``type`` field of the
>> +:c:type:`v4l2_format` structure to ``V4L2_BUF_TYPE_AUDIO_CAPTURE`` or to
>> +``V4L2_BUF_TYPE_AUDIO_OUTPUT``. Both drivers and applications must set the
>> +remainder of the :c:type:`v4l2_format` structure to 0.
>> +
>> +.. c:type:: v4l2_audio_format
>> +
>> +.. tabularcolumns:: |p{1.4cm}|p{2.4cm}|p{13.5cm}|
>> +
>> +.. flat-table:: struct v4l2_audio_format
>> +    :header-rows:  0
>> +    :stub-columns: 0
>> +    :widths:       1 1 2
>> +
>> +    * - __u32
>> +      - ``pixelformat``
>> +      - The sample format, set by the application. see :ref:`pixfmt-audio`
> 
> pixelformat doesn't make any sense for audio: there are no pixels on a

Ah, that's a doc bug: this field is called audioformat in the struct, not
pixelformat. I missed this one in my review.

Regards,

	Hans

> PCM stream. Please use call it, instead: `snd_pcm_format`, making it match
> the values for snd_pcm_format_t.
> 
> Yet, I would keep defining it as u32 (or u64?) instead of using a
> typedef int field there (snd_pcm_format_t), as the size of integer
> is different on 32 and 64 bit kernels.
> 
> 
>> +    * - __u32
>> +      - ``channels``
>> +      - The channel number, set by the application. channel number range is
>> +        [1, 32].
> 
> Why not start on zero?
> 
>> +    * - __u32
>> +      - ``buffersize``
>> +      - Maximum buffer size in bytes required for data. The value is set by the
>> +        driver.
>> diff --git a/Documentation/userspace-api/media/v4l/devices.rst b/Documentation/userspace-api/media/v4l/devices.rst
>> index 8bfbad65a9d4..758bd90f1c26 100644
>> --- a/Documentation/userspace-api/media/v4l/devices.rst
>> +++ b/Documentation/userspace-api/media/v4l/devices.rst
>> @@ -24,3 +24,4 @@ Interfaces
>>      dev-event
>>      dev-subdev
>>      dev-meta
>> +    dev-audio-mem2mem
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> index 000c154b0f98..42deb07f4ff4 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
>> @@ -96,6 +96,8 @@ the ``mbus_code`` field is handled differently:
>>  	``V4L2_BUF_TYPE_VIDEO_OVERLAY``,
>>  	``V4L2_BUF_TYPE_SDR_CAPTURE``,
>>  	``V4L2_BUF_TYPE_SDR_OUTPUT``,
>> +	``V4L2_BUF_TYPE_AUDIO_CAPTURE``,
>> +	``V4L2_BUF_TYPE_AUDIO_OUTPUT``,
>>  	``V4L2_BUF_TYPE_META_CAPTURE`` and
>>  	``V4L2_BUF_TYPE_META_OUTPUT``.
>>  	See :c:type:`v4l2_buf_type`.
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-g-fmt.rst
>> index 675c385e5aca..528fd9df41aa 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-g-fmt.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-g-fmt.rst
>> @@ -130,6 +130,10 @@ The format as returned by :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` must be identical
>>        - ``meta``
>>        - Definition of a metadata format, see :ref:`meta-formats`, used by
>>  	metadata capture devices.
>> +    * - struct :c:type:`v4l2_audio_format`
>> +      - ``audio``
>> +      - Definition of a audio data format, see :ref:`audiomem2mem`, used by
>> +        audio memory-to-memory devices
>>      * - __u8
>>        - ``raw_data``\ [200]
>>        - Place holder for future extensions.
>> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> index da6d0b8e4c2c..e61152bb80d1 100644
>> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>> @@ -29,6 +29,8 @@ replace symbol V4L2_FIELD_SEQ_TB :c:type:`v4l2_field`
>>  replace symbol V4L2_FIELD_TOP :c:type:`v4l2_field`
>>  
>>  # Documented enum v4l2_buf_type
>> +replace symbol V4L2_BUF_TYPE_AUDIO_CAPTURE :c:type:`v4l2_buf_type`
>> +replace symbol V4L2_BUF_TYPE_AUDIO_OUTPUT :c:type:`v4l2_buf_type`
>>  replace symbol V4L2_BUF_TYPE_META_CAPTURE :c:type:`v4l2_buf_type`
>>  replace symbol V4L2_BUF_TYPE_META_OUTPUT :c:type:`v4l2_buf_type`
>>  replace symbol V4L2_BUF_TYPE_SDR_CAPTURE :c:type:`v4l2_buf_type`
>> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> index 54d572c3b515..16ab204d15b0 100644
>> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
>> @@ -791,6 +791,10 @@ int vb2_create_bufs(struct vb2_queue *q, struct v4l2_create_buffers *create)
>>  	case V4L2_BUF_TYPE_META_OUTPUT:
>>  		requested_sizes[0] = f->fmt.meta.buffersize;
>>  		break;
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		requested_sizes[0] = f->fmt.audio.buffersize;
>> +		break;
>>  	default:
>>  		return -EINVAL;
>>  	}
>> diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
>> index 8c07400bd280..5e94db8dfdae 100644
>> --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
>> +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
>> @@ -101,6 +101,7 @@ struct v4l2_format32 {
>>  		struct v4l2_sliced_vbi_format	sliced;
>>  		struct v4l2_sdr_format	sdr;
>>  		struct v4l2_meta_format	meta;
>> +		struct v4l2_audio_format	audio;
>>  		__u8	raw_data[200];        /* user-defined */
>>  	} fmt;
>>  };
>> @@ -166,6 +167,10 @@ static int get_v4l2_format32(struct v4l2_format *p64,
>>  	case V4L2_BUF_TYPE_META_OUTPUT:
>>  		return copy_from_user(&p64->fmt.meta, &p32->fmt.meta,
>>  				      sizeof(p64->fmt.meta)) ? -EFAULT : 0;
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		return copy_from_user(&p64->fmt.audio, &p32->fmt.audio,
>> +				      sizeof(p64->fmt.audio)) ? -EFAULT : 0;
>>  	default:
>>  		return -EINVAL;
>>  	}
>> @@ -216,6 +221,10 @@ static int put_v4l2_format32(struct v4l2_format *p64,
>>  	case V4L2_BUF_TYPE_META_OUTPUT:
>>  		return copy_to_user(&p32->fmt.meta, &p64->fmt.meta,
>>  				    sizeof(p64->fmt.meta)) ? -EFAULT : 0;
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		return copy_to_user(&p32->fmt.audio, &p64->fmt.audio,
>> +				    sizeof(p64->fmt.audio)) ? -EFAULT : 0;
>>  	default:
>>  		return -EINVAL;
>>  	}
>> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
>> index d13954bd31fd..bac008fcedc6 100644
>> --- a/drivers/media/v4l2-core/v4l2-dev.c
>> +++ b/drivers/media/v4l2-core/v4l2-dev.c
>> @@ -553,6 +553,7 @@ static void determine_valid_ioctls(struct video_device *vdev)
>>  	bool is_tch = vdev->vfl_type == VFL_TYPE_TOUCH;
>>  	bool is_meta = vdev->vfl_type == VFL_TYPE_VIDEO &&
>>  		       (vdev->device_caps & meta_caps);
>> +	bool is_audio = vdev->vfl_type == VFL_TYPE_AUDIO;
>>  	bool is_rx = vdev->vfl_dir != VFL_DIR_TX;
>>  	bool is_tx = vdev->vfl_dir != VFL_DIR_RX;
>>  	bool is_io_mc = vdev->device_caps & V4L2_CAP_IO_MC;
>> @@ -666,6 +667,19 @@ static void determine_valid_ioctls(struct video_device *vdev)
>>  		SET_VALID_IOCTL(ops, VIDIOC_S_FMT, vidioc_s_fmt_meta_out);
>>  		SET_VALID_IOCTL(ops, VIDIOC_TRY_FMT, vidioc_try_fmt_meta_out);
>>  	}
>> +	if (is_audio && is_rx) {
>> +		/* audio capture specific ioctls */
>> +		SET_VALID_IOCTL(ops, VIDIOC_ENUM_FMT, vidioc_enum_fmt_audio_cap);
>> +		SET_VALID_IOCTL(ops, VIDIOC_G_FMT, vidioc_g_fmt_audio_cap);
>> +		SET_VALID_IOCTL(ops, VIDIOC_S_FMT, vidioc_s_fmt_audio_cap);
>> +		SET_VALID_IOCTL(ops, VIDIOC_TRY_FMT, vidioc_try_fmt_audio_cap);
>> +	} else if (is_audio && is_tx) {
>> +		/* audio output specific ioctls */
>> +		SET_VALID_IOCTL(ops, VIDIOC_ENUM_FMT, vidioc_enum_fmt_audio_out);
>> +		SET_VALID_IOCTL(ops, VIDIOC_G_FMT, vidioc_g_fmt_audio_out);
>> +		SET_VALID_IOCTL(ops, VIDIOC_S_FMT, vidioc_s_fmt_audio_out);
>> +		SET_VALID_IOCTL(ops, VIDIOC_TRY_FMT, vidioc_try_fmt_audio_out);
>> +	}
>>  	if (is_vbi) {
>>  		/* vbi specific ioctls */
>>  		if ((is_rx && (ops->vidioc_g_fmt_vbi_cap ||
>> @@ -929,6 +943,9 @@ int __video_register_device(struct video_device *vdev,
>>  	case VFL_TYPE_TOUCH:
>>  		name_base = "v4l-touch";
>>  		break;
>> +	case VFL_TYPE_AUDIO:
>> +		name_base = "v4l-audio";
>> +		break;
>>  	default:
>>  		pr_err("%s called with unknown type: %d\n",
>>  		       __func__, type);
>> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
>> index 33076af4dfdb..e7be7c2f302d 100644
>> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
>> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
>> @@ -188,6 +188,8 @@ const char *v4l2_type_names[] = {
>>  	[V4L2_BUF_TYPE_SDR_OUTPUT]         = "sdr-out",
>>  	[V4L2_BUF_TYPE_META_CAPTURE]       = "meta-cap",
>>  	[V4L2_BUF_TYPE_META_OUTPUT]	   = "meta-out",
>> +	[V4L2_BUF_TYPE_AUDIO_CAPTURE]      = "audio-cap",
>> +	[V4L2_BUF_TYPE_AUDIO_OUTPUT]	   = "audio-out",
>>  };
>>  EXPORT_SYMBOL(v4l2_type_names);
>>  
>> @@ -276,6 +278,7 @@ static void v4l_print_format(const void *arg, bool write_only)
>>  	const struct v4l2_sliced_vbi_format *sliced;
>>  	const struct v4l2_window *win;
>>  	const struct v4l2_meta_format *meta;
>> +	const struct v4l2_audio_format *audio;
>>  	u32 pixelformat;
>>  	u32 planes;
>>  	unsigned i;
>> @@ -346,6 +349,13 @@ static void v4l_print_format(const void *arg, bool write_only)
>>  		pr_cont(", dataformat=%p4cc, buffersize=%u\n",
>>  			&pixelformat, meta->buffersize);
>>  		break;
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		audio = &p->fmt.audio;
>> +		pixelformat = audio->audioformat;
>> +		pr_cont(", format=%p4cc, channels=%u, buffersize=%u\n",
>> +			&pixelformat, audio->channels, audio->buffersize);
>> +		break;
>>  	}
>>  }
>>  
>> @@ -927,6 +937,7 @@ static int check_fmt(struct file *file, enum v4l2_buf_type type)
>>  	bool is_tch = vfd->vfl_type == VFL_TYPE_TOUCH;
>>  	bool is_meta = vfd->vfl_type == VFL_TYPE_VIDEO &&
>>  		       (vfd->device_caps & meta_caps);
>> +	bool is_audio = vfd->vfl_type == VFL_TYPE_AUDIO;
>>  	bool is_rx = vfd->vfl_dir != VFL_DIR_TX;
>>  	bool is_tx = vfd->vfl_dir != VFL_DIR_RX;
>>  
>> @@ -992,6 +1003,14 @@ static int check_fmt(struct file *file, enum v4l2_buf_type type)
>>  		if (is_meta && is_tx && ops->vidioc_g_fmt_meta_out)
>>  			return 0;
>>  		break;
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +		if (is_audio && is_rx && ops->vidioc_g_fmt_audio_cap)
>> +			return 0;
>> +		break;
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		if (is_audio && is_tx && ops->vidioc_g_fmt_audio_out)
>> +			return 0;
>> +		break;
>>  	default:
>>  		break;
>>  	}
>> @@ -1597,6 +1616,16 @@ static int v4l_enum_fmt(const struct v4l2_ioctl_ops *ops,
>>  			break;
>>  		ret = ops->vidioc_enum_fmt_meta_out(file, fh, arg);
>>  		break;
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +		if (unlikely(!ops->vidioc_enum_fmt_audio_cap))
>> +			break;
>> +		ret = ops->vidioc_enum_fmt_audio_cap(file, fh, arg);
>> +		break;
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		if (unlikely(!ops->vidioc_enum_fmt_audio_out))
>> +			break;
>> +		ret = ops->vidioc_enum_fmt_audio_out(file, fh, arg);
>> +		break;
>>  	}
>>  	if (ret == 0)
>>  		v4l_fill_fmtdesc(p);
>> @@ -1673,6 +1702,10 @@ static int v4l_g_fmt(const struct v4l2_ioctl_ops *ops,
>>  		return ops->vidioc_g_fmt_meta_cap(file, fh, arg);
>>  	case V4L2_BUF_TYPE_META_OUTPUT:
>>  		return ops->vidioc_g_fmt_meta_out(file, fh, arg);
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +		return ops->vidioc_g_fmt_audio_cap(file, fh, arg);
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		return ops->vidioc_g_fmt_audio_out(file, fh, arg);
>>  	}
>>  	return -EINVAL;
>>  }
>> @@ -1784,6 +1817,16 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
>>  			break;
>>  		memset_after(p, 0, fmt.meta);
>>  		return ops->vidioc_s_fmt_meta_out(file, fh, arg);
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +		if (unlikely(!ops->vidioc_s_fmt_audio_cap))
>> +			break;
>> +		memset_after(p, 0, fmt.audio);
>> +		return ops->vidioc_s_fmt_audio_cap(file, fh, arg);
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		if (unlikely(!ops->vidioc_s_fmt_audio_out))
>> +			break;
>> +		memset_after(p, 0, fmt.audio);
>> +		return ops->vidioc_s_fmt_audio_out(file, fh, arg);
>>  	}
>>  	return -EINVAL;
>>  }
>> @@ -1892,6 +1935,16 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
>>  			break;
>>  		memset_after(p, 0, fmt.meta);
>>  		return ops->vidioc_try_fmt_meta_out(file, fh, arg);
>> +	case V4L2_BUF_TYPE_AUDIO_CAPTURE:
>> +		if (unlikely(!ops->vidioc_try_fmt_audio_cap))
>> +			break;
>> +		memset_after(p, 0, fmt.audio);
>> +		return ops->vidioc_try_fmt_audio_cap(file, fh, arg);
>> +	case V4L2_BUF_TYPE_AUDIO_OUTPUT:
>> +		if (unlikely(!ops->vidioc_try_fmt_audio_out))
>> +			break;
>> +		memset_after(p, 0, fmt.audio);
>> +		return ops->vidioc_try_fmt_audio_out(file, fh, arg);
>>  	}
>>  	return -EINVAL;
>>  }
>> diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
>> index d82dfdbf6e58..82b63f82d43f 100644
>> --- a/include/media/v4l2-dev.h
>> +++ b/include/media/v4l2-dev.h
>> @@ -30,6 +30,7 @@
>>   * @VFL_TYPE_SUBDEV:	for V4L2 subdevices
>>   * @VFL_TYPE_SDR:	for Software Defined Radio tuners
>>   * @VFL_TYPE_TOUCH:	for touch sensors
>> + * @VFL_TYPE_AUDIO:	for audio memory-to-memory devices
>>   * @VFL_TYPE_MAX:	number of VFL types, must always be last in the enum
>>   */
>>  enum vfl_devnode_type {
>> @@ -39,6 +40,7 @@ enum vfl_devnode_type {
>>  	VFL_TYPE_SUBDEV,
>>  	VFL_TYPE_SDR,
>>  	VFL_TYPE_TOUCH,
>> +	VFL_TYPE_AUDIO,
>>  	VFL_TYPE_MAX /* Shall be the last one */
>>  };
>>  
>> diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
>> index edb733f21604..f840cf740ce1 100644
>> --- a/include/media/v4l2-ioctl.h
>> +++ b/include/media/v4l2-ioctl.h
>> @@ -45,6 +45,12 @@ struct v4l2_fh;
>>   * @vidioc_enum_fmt_meta_out: pointer to the function that implements
>>   *	:ref:`VIDIOC_ENUM_FMT <vidioc_enum_fmt>` ioctl logic
>>   *	for metadata output
>> + * @vidioc_enum_fmt_audio_cap: pointer to the function that implements
>> + *	:ref:`VIDIOC_ENUM_FMT <vidioc_enum_fmt>` ioctl logic
>> + *	for audio capture
>> + * @vidioc_enum_fmt_audio_out: pointer to the function that implements
>> + *	:ref:`VIDIOC_ENUM_FMT <vidioc_enum_fmt>` ioctl logic
>> + *	for audio output
>>   * @vidioc_g_fmt_vid_cap: pointer to the function that implements
>>   *	:ref:`VIDIOC_G_FMT <vidioc_g_fmt>` ioctl logic for video capture
>>   *	in single plane mode
>> @@ -79,6 +85,10 @@ struct v4l2_fh;
>>   *	:ref:`VIDIOC_G_FMT <vidioc_g_fmt>` ioctl logic for metadata capture
>>   * @vidioc_g_fmt_meta_out: pointer to the function that implements
>>   *	:ref:`VIDIOC_G_FMT <vidioc_g_fmt>` ioctl logic for metadata output
>> + * @vidioc_g_fmt_audio_cap: pointer to the function that implements
>> + *	:ref:`VIDIOC_G_FMT <vidioc_g_fmt>` ioctl logic for audio capture
>> + * @vidioc_g_fmt_audio_out: pointer to the function that implements
>> + *	:ref:`VIDIOC_G_FMT <vidioc_g_fmt>` ioctl logic for audio output
>>   * @vidioc_s_fmt_vid_cap: pointer to the function that implements
>>   *	:ref:`VIDIOC_S_FMT <vidioc_g_fmt>` ioctl logic for video capture
>>   *	in single plane mode
>> @@ -113,6 +123,10 @@ struct v4l2_fh;
>>   *	:ref:`VIDIOC_S_FMT <vidioc_g_fmt>` ioctl logic for metadata capture
>>   * @vidioc_s_fmt_meta_out: pointer to the function that implements
>>   *	:ref:`VIDIOC_S_FMT <vidioc_g_fmt>` ioctl logic for metadata output
>> + * @vidioc_s_fmt_audio_cap: pointer to the function that implements
>> + *	:ref:`VIDIOC_S_FMT <vidioc_g_fmt>` ioctl logic for audio capture
>> + * @vidioc_s_fmt_audio_out: pointer to the function that implements
>> + *	:ref:`VIDIOC_S_FMT <vidioc_g_fmt>` ioctl logic for audio output
>>   * @vidioc_try_fmt_vid_cap: pointer to the function that implements
>>   *	:ref:`VIDIOC_TRY_FMT <vidioc_g_fmt>` ioctl logic for video capture
>>   *	in single plane mode
>> @@ -149,6 +163,10 @@ struct v4l2_fh;
>>   *	:ref:`VIDIOC_TRY_FMT <vidioc_g_fmt>` ioctl logic for metadata capture
>>   * @vidioc_try_fmt_meta_out: pointer to the function that implements
>>   *	:ref:`VIDIOC_TRY_FMT <vidioc_g_fmt>` ioctl logic for metadata output
>> + * @vidioc_try_fmt_audio_cap: pointer to the function that implements
>> + *	:ref:`VIDIOC_TRY_FMT <vidioc_g_fmt>` ioctl logic for audio capture
>> + * @vidioc_try_fmt_audio_out: pointer to the function that implements
>> + *	:ref:`VIDIOC_TRY_FMT <vidioc_g_fmt>` ioctl logic for audio output
>>   * @vidioc_reqbufs: pointer to the function that implements
>>   *	:ref:`VIDIOC_REQBUFS <vidioc_reqbufs>` ioctl
>>   * @vidioc_querybuf: pointer to the function that implements
>> @@ -315,6 +333,10 @@ struct v4l2_ioctl_ops {
>>  					struct v4l2_fmtdesc *f);
>>  	int (*vidioc_enum_fmt_meta_out)(struct file *file, void *fh,
>>  					struct v4l2_fmtdesc *f);
>> +	int (*vidioc_enum_fmt_audio_cap)(struct file *file, void *fh,
>> +					 struct v4l2_fmtdesc *f);
>> +	int (*vidioc_enum_fmt_audio_out)(struct file *file, void *fh,
>> +					 struct v4l2_fmtdesc *f);
>>  
>>  	/* VIDIOC_G_FMT handlers */
>>  	int (*vidioc_g_fmt_vid_cap)(struct file *file, void *fh,
>> @@ -345,6 +367,10 @@ struct v4l2_ioctl_ops {
>>  				     struct v4l2_format *f);
>>  	int (*vidioc_g_fmt_meta_out)(struct file *file, void *fh,
>>  				     struct v4l2_format *f);
>> +	int (*vidioc_g_fmt_audio_cap)(struct file *file, void *fh,
>> +				      struct v4l2_format *f);
>> +	int (*vidioc_g_fmt_audio_out)(struct file *file, void *fh,
>> +				      struct v4l2_format *f);
>>  
>>  	/* VIDIOC_S_FMT handlers */
>>  	int (*vidioc_s_fmt_vid_cap)(struct file *file, void *fh,
>> @@ -375,6 +401,10 @@ struct v4l2_ioctl_ops {
>>  				     struct v4l2_format *f);
>>  	int (*vidioc_s_fmt_meta_out)(struct file *file, void *fh,
>>  				     struct v4l2_format *f);
>> +	int (*vidioc_s_fmt_audio_cap)(struct file *file, void *fh,
>> +				      struct v4l2_format *f);
>> +	int (*vidioc_s_fmt_audio_out)(struct file *file, void *fh,
>> +				      struct v4l2_format *f);
>>  
>>  	/* VIDIOC_TRY_FMT handlers */
>>  	int (*vidioc_try_fmt_vid_cap)(struct file *file, void *fh,
>> @@ -405,6 +435,10 @@ struct v4l2_ioctl_ops {
>>  				       struct v4l2_format *f);
>>  	int (*vidioc_try_fmt_meta_out)(struct file *file, void *fh,
>>  				       struct v4l2_format *f);
>> +	int (*vidioc_try_fmt_audio_cap)(struct file *file, void *fh,
>> +					struct v4l2_format *f);
>> +	int (*vidioc_try_fmt_audio_out)(struct file *file, void *fh,
>> +					struct v4l2_format *f);
>>  
>>  	/* Buffer handlers */
>>  	int (*vidioc_reqbufs)(struct file *file, void *fh,
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 6cd65969c2b5..57c82eb158f1 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -153,6 +153,8 @@ enum v4l2_buf_type {
>>  	V4L2_BUF_TYPE_SDR_OUTPUT           = 12,
>>  	V4L2_BUF_TYPE_META_CAPTURE         = 13,
>>  	V4L2_BUF_TYPE_META_OUTPUT	   = 14,
>> +	V4L2_BUF_TYPE_AUDIO_CAPTURE        = 15,
>> +	V4L2_BUF_TYPE_AUDIO_OUTPUT         = 16,
>>  	/* Deprecated, do not use */
>>  	V4L2_BUF_TYPE_PRIVATE              = 0x80,
>>  };
>> @@ -169,6 +171,7 @@ enum v4l2_buf_type {
>>  	 || (type) == V4L2_BUF_TYPE_VBI_OUTPUT			\
>>  	 || (type) == V4L2_BUF_TYPE_SLICED_VBI_OUTPUT		\
>>  	 || (type) == V4L2_BUF_TYPE_SDR_OUTPUT			\
>> +	 || (type) == V4L2_BUF_TYPE_AUDIO_OUTPUT		\
>>  	 || (type) == V4L2_BUF_TYPE_META_OUTPUT)
>>  
>>  #define V4L2_TYPE_IS_CAPTURE(type) (!V4L2_TYPE_IS_OUTPUT(type))
>> @@ -2423,6 +2426,18 @@ struct v4l2_meta_format {
>>  	__u32				buffersize;
>>  } __attribute__ ((packed));
>>  
>> +/**
>> + * struct v4l2_audio_format - audio data format definition
>> + * @audioformat:	little endian four character code (fourcc)
> 
> Don't use fourcc here. Instead, use the types defined at snd_pcm_format_t.
> 
>> + * @channels:		channel numbers
>> + * @buffersize:		maximum size in bytes required for data
>> + */
>> +struct v4l2_audio_format {
>> +	__u32				audioformat;
>> +	__u32				channels;
>> +	__u32				buffersize;
>> +} __attribute__ ((packed));
>> +
>>  /**
>>   * struct v4l2_format - stream data format
>>   * @type:	enum v4l2_buf_type; type of the data stream
>> @@ -2431,6 +2446,7 @@ struct v4l2_meta_format {
>>   * @win:	definition of an overlaid image
>>   * @vbi:	raw VBI capture or output parameters
>>   * @sliced:	sliced VBI capture or output parameters
>> + * @audio:	definition of an audio format
>>   * @raw_data:	placeholder for future extensions and custom formats
>>   * @fmt:	union of @pix, @pix_mp, @win, @vbi, @sliced, @sdr, @meta
>>   *		and @raw_data
>> @@ -2445,6 +2461,7 @@ struct v4l2_format {
>>  		struct v4l2_sliced_vbi_format	sliced;  /* V4L2_BUF_TYPE_SLICED_VBI_CAPTURE */
>>  		struct v4l2_sdr_format		sdr;     /* V4L2_BUF_TYPE_SDR_CAPTURE */
>>  		struct v4l2_meta_format		meta;    /* V4L2_BUF_TYPE_META_CAPTURE */
>> +		struct v4l2_audio_format	audio;   /* V4L2_BUF_TYPE_AUDIO_CAPTURE */
>>  		__u8	raw_data[200];                   /* user-defined */
>>  	} fmt;
>>  };
> 
> 
> 
> Thanks,
> Mauro