by Shengjiu Wang

[permalink] [raw]

Subject: Re: [RFC PATCH v3 6/9] media: v4l2: Add audio capture and output support

On Wed, Sep 20, 2023 at 6:12 PM Hans Verkuil <[email protected]> wrote:
>
> Hi Shengjiu,
>
> I just noticed you posted a v4, but I expect that my comments below are still valid...
>
> On 14/09/2023 07:54, 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.
> >
> > 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 <[email protected]>
> > ---
> > .../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
>
> Rename the file to dev-audio-mem2mem.rst as this is specific to an audio
> M2M interface.
>
> > @@ -0,0 +1,63 @@
> > +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> > +
> > +.. _audiodev:
> > +
> > +******************
> > +audio Interface
> > +******************
> > +
> > +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``
>
> I think this intro is somewhat confusing. I would recommend to copy the intro
> from dev-mem2mem.rst instead, adapting it for 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.
>
> M2M devices do not support read/write, only streaming I/O is 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
> > + * - u32 channels;
> > + - channel number for each sample.
>
> See Sakari's comments. This section describes how the audio data is formatted
> in the buffer memory. Presumably this is already documented somewhere in the ALSA
> docs, so a reference to that would work.
>
> > diff --git a/Documentation/userspace-api/media/v4l/pixfmt.rst b/Documentation/userspace-api/media/v4l/pixfmt.rst
> > index 11dab4a90630..e205db5fa8af 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
> > + audio-formats
> > 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..1ecb7d640057 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:`dev-audio`, used by
> > + audio capture and output devices
> > * - __u8
> > - ``raw_data``\ [200]
> > - Place holder for future extensions.
> > diff --git a/Documentation/userspace-api/media/v4l/vidioc-querycap.rst b/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> > index 6c57b8428356..0b3cefefc86b 100644
> > --- a/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> > +++ b/Documentation/userspace-api/media/v4l/vidioc-querycap.rst
> > @@ -259,6 +259,9 @@ specification the ioctl returns an ``EINVAL`` error code.
> > video topology configuration, including which I/O entity is routed to
> > the input/output, is configured by userspace via the Media Controller.
> > See :ref:`media_controller`.
> > + * - ``V4L2_CAP_AUDIO_M2M``
> > + - 0x40000000
> > + - The device supports the audio Memory-To-Memory interface.
> > * - ``V4L2_CAP_DEVICE_CAPS``
> > - 0x80000000
> > - The driver fills the ``device_caps`` field. This capability can
> > diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> > index 3e58aac4ef0b..48ef3bce3d20 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 c7a54d82a55e..12f2be2773a2 100644
> > --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > @@ -785,6 +785,10 @@ 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-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> > index f81279492682..b92c760b611a 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;
> > @@ -664,6 +665,19 @@ 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 ||
> > @@ -927,6 +941,9 @@ 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 f4d9d6279094..767588d5822a 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 +349,12 @@ 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;
> > + pr_cont(", rate=%u, format=%u, channels=%u, buffersize=%u\n",
> > + audio->rate, audio->format, audio->channels, audio->buffersize);
> > + break;
> > }
> > }
> >
> > @@ -927,6 +936,7 @@ 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 +1002,14 @@ 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;
> > }
> > @@ -1452,6 +1470,7 @@ 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_LPCM: descr = "Audio LPCM"; break;
> >
> > default:
> > /* Compressed formats */
> > @@ -1596,6 +1615,16 @@ 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);
> > @@ -1672,6 +1701,10 @@ 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;
> > }
> > @@ -1783,6 +1816,16 @@ 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;
> > }
> > @@ -1891,6 +1934,16 @@ 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 e0a13505f88d..0924e6d1dab1 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 input/output devices
>
> Change this to: "for audio memory-to-memory devices"
> That's the only audio type we support at the moment. I don't see a need
> for pure capture or output audio devices, since that would be handled in
> alsa.
>
> > * @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 78260e5d9985..8dc615f2b60c 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))
> > @@ -508,6 +511,7 @@ struct v4l2_capability {
> > #define V4L2_CAP_TOUCH 0x10000000 /* Is a touch device */
> >
> > #define V4L2_CAP_IO_MC 0x20000000 /* Is input/output controlled by the media controller */
> > +#define V4L2_CAP_AUDIO_M2M 0x40000000
> >
> > #define V4L2_CAP_DEVICE_CAPS 0x80000000 /* sets device capabilities field */
> >
> > @@ -838,6 +842,9 @@ 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 */
> > +#define V4L2_AUDIO_FMT_LPCM v4l2_fourcc('L', 'P', 'C', 'M') /* audio lpcm */
> > +
>
> Hmm, this I am uncertain about. This doesn't add anything. If you enumerate the
> formats, they will all report just this format, so you still don't know which
> actual audio formats are supported.
>
> The real audio format is the 'format' field.
>
> > /* priv field value to indicates that subsequent fields are valid. */
> > #define V4L2_PIX_FMT_PRIV_MAGIC 0xfeedcafe
> >
> > @@ -2417,6 +2424,22 @@ struct v4l2_meta_format {
> > __u32 buffersize;
> > } __attribute__ ((packed));
> >
> > +/**
> > + * struct v4l2_audio_format - audio data format definition
> > + * @pixelformat: little endian four character code (fourcc)
> > + * @rate: sample rate
> > + * @format: sample format
> > + * @channels: channel numbers
> > + * @buffersize: maximum size in bytes required for data
> > + */
> > +struct v4l2_audio_format {
> > + __u32 pixelformat;
>
> Why not just drop this field, and instead use the format field?
>
> You would have to update the ENUM_FMT documentation to indicate that for
> audio m2m device the pixelformat field of v4l2_fmtdesc is actually the
> audio format, and that it is not a fourcc, but a SNDRV_PCM_FORMAT_ format.
>
> v4l_fill_fmtdesc can just add 'case SNDRV_PCM_FORMAT_U8:' etc., since they
> luckily won't conflict with the existing fourccs as far as I can tell.
>
> One problem might be the use of %p4cc as a printf formatter for fourcc
> values, that would fail with these formats.
>
> One option to solve this could be to add a define to videodev2.h that converts
> a SNDRV_PCM_FORMAT_* to a fourcc, e.g.:
>
> #define v4l2_fourcc_pcm(pcm_fmt) v4l2_fourcc('A', 'U', (pcm_fmt) / 10 + '0', (pcm_fmt) % 10 + '0')
>
> So all audio formats end up like 'ADXX' where XX is the SNDRV_PCM_FORMAT_* value.
>
> You would also need a define to translate a fourcc back to a pcm format.
>
> This scheme would allow %p4cc to continue to be used. Alternatively, you need
> to check all places where %p4cc is used in the media subsystem core and see if
> you need to check if it is an audio buffer type, and if so, just use %u.
>
> I'm not quite sure which of the two options is best.
>
> More input on this would be welcome.

One thing I try to avoid is to include the asound.h, which has the
definition of
'format', 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.

Another reason for adding V4L2_AUDIO_FMT_LPCM, I think use LPCM is
general for audio cases, maybe in the future there will be a requirement for
non-PCM, like MP3/AAC format.

If use SNDRV_PCM_FORMAT_*, there will be a lot of pixfmt need to be added.
a little complicated:)

'format' field is one character of LPCM. From this point of view, it seems LPCM
is simple.

Best regards
Wang shengjiu

>
> > + __u32 rate;
> > + __u32 format;
> > + __u32 channels;
> > + __u32 buffersize;
> > +} __attribute__ ((packed));
> > +
> > /**
> > * struct v4l2_format - stream data format
> > * @type: enum v4l2_buf_type; type of the data stream
> > @@ -2425,6 +2448,7 @@ 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
> > @@ -2439,6 +2463,7 @@ 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;
> > };
>
> Regards,
>
> Hans