Hi Shenjiu,
Thanks for the update.
On Thu, Sep 14, 2023 at 01:54:02PM +0800, Shengjiu Wang wrote:
> 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.
>
> Defined V4L2_AUDIO_FMT_LPCM format type for audio.
This would be nicer as a separate patch. Also see the related comments
below.
>
> Defined V4L2_CAP_AUDIO_M2M capability type for audio memory
> to memory case.
>
> The created audio device is named "/dev/v4l-audioX".
>
> Signed-off-by: Shengjiu Wang <shengjiu.w...@nxp.com>
> ---
> .../userspace-api/media/v4l/audio-formats.rst | 15 +++++
> .../userspace-api/media/v4l/buffer.rst | 6 ++
> .../userspace-api/media/v4l/dev-audio.rst | 63 +++++++++++++++++++
> .../userspace-api/media/v4l/devices.rst | 1 +
> .../media/v4l/pixfmt-aud-lpcm.rst | 31 +++++++++
> .../userspace-api/media/v4l/pixfmt.rst | 1 +
> .../media/v4l/vidioc-enum-fmt.rst | 2 +
> .../userspace-api/media/v4l/vidioc-g-fmt.rst | 4 ++
> .../media/v4l/vidioc-querycap.rst | 3 +
> .../media/videodev2.h.rst.exceptions | 2 +
> .../media/common/videobuf2/videobuf2-v4l2.c | 4 ++
> 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 | 25 ++++++++
> 16 files changed, 263 insertions(+)
> create mode 100644 Documentation/userspace-api/media/v4l/audio-formats.rst
> create mode 100644 Documentation/userspace-api/media/v4l/dev-audio.rst
> create mode 100644 Documentation/userspace-api/media/v4l/pixfmt-aud-lpcm.rst
>
> diff --git a/Documentation/userspace-api/media/v4l/audio-formats.rst
> b/Documentation/userspace-api/media/v4l/audio-formats.rst
> new file mode 100644
> index 000000000000..bc52712d20d3
> --- /dev/null
> +++ b/Documentation/userspace-api/media/v4l/audio-formats.rst
> @@ -0,0 +1,15 @@
> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> +
> +.. _audio-formats:
> +
> +*************
> +Audio Formats
> +*************
> +
> +These formats are used for :ref:`audio` interface only.
> +
> +
> +.. toctree::
> + :maxdepth: 1
> +
> + pixfmt-aud-lpcm
> diff --git a/Documentation/userspace-api/media/v4l/buffer.rst
> b/Documentation/userspace-api/media/v4l/buffer.rst
> index 04dec3e570ed..80cf2cb20dfe 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
> + - Buffer for audio output, see :ref:`audio`.
>
>
> .. _buffer-flags:
> diff --git a/Documentation/userspace-api/media/v4l/dev-audio.rst
> b/Documentation/userspace-api/media/v4l/dev-audio.rst
> new file mode 100644
> index 000000000000..f9bcf0c7b056
> --- /dev/null
> +++ b/Documentation/userspace-api/media/v4l/dev-audio.rst
> @@ -0,0 +1,63 @@
> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> +
> +.. _audiodev:
> +
> +******************
> +audio Interface
Capital "A"?
> +******************
Too many asterisks (same a few lines above, too).
> +
> +The audio interface is implemented on audio device nodes. The audio device
> +which uses application software for modulation or demodulation. This
> +interface is intended for controlling and data streaming of such devices
> +
> +Audio devices are accessed through character device special files named
> +``/dev/v4l-audio``
> +
> +Querying Capabilities
> +=====================
> +
> +Device nodes supporting the audio capture and output 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.
> +
> +At least one of the read/write or streaming I/O methods must be supported.
> +
> +
> +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
> + - ``rate``
> + - The sample rate, set by the application. The range is [5512, 768000].
> + * - __u32
> + - ``format``
> + - The sample format, set by the application. format is defined as
> + SNDRV_PCM_FORMAT_S8, SNDRV_PCM_FORMAT_U8, ...,
> + * - __u32
> + - ``channels``
> + - The channel number, set by the application. channel number range is
> + [1, 32].
> + * - __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..8261f3468489 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
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-aud-lpcm.rst
> b/Documentation/userspace-api/media/v4l/pixfmt-aud-lpcm.rst
> new file mode 100644
> index 000000000000..f9ebe2a05f69
> --- /dev/null
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-aud-lpcm.rst
> @@ -0,0 +1,31 @@
> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> +
> +.. _v4l2-aud-fmt-lpcm:
> +
> +*************************
> +V4L2_AUDIO_FMT_LPCM ('LPCM')
> +*************************
> +
> +Linear Pulse-Code Modulation (LPCM)
> +
> +
> +Description
> +===========
> +
> +This describes audio format used by the audio memory to memory driver.
> +
> +It contains the following fields:
> +
> +.. flat-table::
> + :widths: 1 4
> + :header-rows: 1
> + :stub-columns: 0
> +
> + * - Field
> + - Description
> + * - u32 samplerate;
> + - which is the number of times per second that samples are taken.
> + * - u32 sampleformat;
> + - which determines the number of possible digital values that can be
> used to represent each sample
80 characters (or less) per line, please.
Which values could this field have and what do they signify?
> + * - u32 channels;
> + - channel number for each sample.
I suppose the rest of the buffer would be samples? This should be
documented. I think there are also different ways the data could be
arrangeed and this needs to be documented, too.
--
Kind regards,
Sakari Ailus
