[RFC,v4,07/11] media: uapi: Add V4L2_AUDIO_FMT_LPCM fourcc format

Commit Message

Shengjiu Wang Sept. 20, 2023, 9:32 a.m. UTC

Linear Pulse-Code Modulation is used to represent
audio samples in buffer, the samples for each channel
are interleaved.

Signed-off-by: Shengjiu Wang <[e-mail]>
---
 .../userspace-api/media/v4l/audio-formats.rst | 15 +++++
 .../media/v4l/pixfmt-aud-lpcm.rst             | 61 +++++++++++++++++++
 .../userspace-api/media/v4l/pixfmt.rst        |  1 +
 drivers/media/v4l2-core/v4l2-ioctl.c          |  1 +
 include/uapi/linux/videodev2.h                |  3 +
 5 files changed, 81 insertions(+)
 create mode 100644 Documentation/userspace-api/media/v4l/audio-formats.rst
 create mode 100644 Documentation/userspace-api/media/v4l/pixfmt-aud-lpcm.rst

Patch

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/pixfmt-aud-lpcm.rst b/Documentation/userspace-api/media/v4l/pixfmt-aud-lpcm.rst
new file mode 100644
index 000000000000..2231bd95212f
--- /dev/null
+++ b/Documentation/userspace-api/media/v4l/pixfmt-aud-lpcm.rst
@@ -0,0 +1,61 @@ 
+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+
+.. _v4l2-audio-fmt-lpcm:
+
+****************************
+V4L2_AUDIO_FMT_LPCM ('LPCM')
+****************************
+
+Linear Pulse-Code Modulation (LPCM)
+
+
+Description
+===========
+
+LPCM audio is coded using a combination of values such as:
+
+Sample rate: which is the number of times per second that samples are taken,
+The typical rates are 8kHz, 11025Hz, 16kHz, 22050Hz, 32kHz, 44100Hz, 48kHz,
+88200Hz, 96kHz, 176400Hz, 192kHz...
+
+Sample format: which determines the number of possible digital values that
+can be used to represent each sample. The format can be SND_PCM_FORMAT_S8,
+SND_PCM_FORMAT_S16_LE, SND_PCM_FORMAT_S24_LE, SND_PCM_FORMAT_S32_LE...
+
+Channels: It is the "location" or "passageway" of a specific signal or
+data in a piece of audio. The channel number can be 1,2,3...
+
+Please refer to https://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html
+for more detail
+
+Each sample contains several channels data,  the channel data format is
+defined by sample format.
+
+.. flat-table::
+    :header-rows:  0
+    :stub-columns: 0
+
+    * - Sample 0:
+      - Channel 0
+      - Channel 1
+      - Channel 2
+      - Channel 3
+      - ...
+    * - Sample 1:
+      - Channel 0
+      - Channel 1
+      - Channel 2
+      - Channel 3
+      - ...
+    * - Sample 2:
+      - Channel 0
+      - Channel 1
+      - Channel 2
+      - Channel 3
+      - ...
+    * - Sample 3:
+      - Channel 0
+      - Channel 1
+      - Channel 2
+      - Channel 3
+      - ...
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/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index f4d9d6279094..55fd4da10ba6 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -1452,6 +1452,7 @@  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 */
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 3decf7d73870..ce71e9343705 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -839,6 +839,9 @@  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 */
+
 /* priv field value to indicates that subsequent fields are valid. */
 #define V4L2_PIX_FMT_PRIV_MAGIC		0xfeedcafe