On Wed, Feb 21, 2024 at 12:30 PM Tomasz Figa <tfiga@xxxxxxxxxxxx> wrote: > > On Sat, Feb 17, 2024 at 6:42 PM Mauro Carvalho Chehab > <mchehab@xxxxxxxxxx> wrote: > > > > Em Thu, 18 Jan 2024 20:32:00 +0800 > > Shengjiu Wang <shengjiu.wang@xxxxxxx> 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@xxxxxxx> > > > --- > > > .../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 > > > > The API is still V4L2, and all the other non-video buf types also use > the V4L2_ prefix, so perhaps that's good here as well? > > Whether AUDIO or PCM_STREAM makes more sense goes outside of my > expertise. Subjectively, a PCM stream sounds more specific than an > audio stream. Do those buf types also support non-PCM audio streams? Currently I use it for PCM, but I think it can also be used for non-PCM. So use the below name? V4L2_BUF_TYPE_AUDIO_CAPTURE V4L2_BUF_TYPE_AUDIO_PLAYBACK > > > > + - 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 > > PCM stream. Please use call it, instead: `snd_pcm_format`, making it match > > the values for snd_pcm_format_t. > > > > +1 > > FWIW v4l2_meta_format uses the name "dataformat". > > Actually, I just realized that the C code actually uses the name > "audioformat". Tbh., after reading the kerneldoc comment, my > subjective preference would be on "sample_format", since that's > exactly what it is. > Ok, I will change it to sampleformat. Best Regards Shengjiu Wang > > 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. > > +1 > > Best regards, > Tomasz