linux-kernel - [RFC PATCH v2 2/6] ALSA: compress: add new ioctl for setting codec parameters

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Date:   Tue, 21 Jul 2020 18:00:03 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     broonie@...nel.org
Cc:     vkoul@...nel.org, perex@...ex.cz, tiwai@...e.com,
        lgirdwood@...il.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, ckeepax@...nsource.cirrus.com,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: [RFC PATCH v2 2/6] ALSA: compress: add new ioctl for setting codec parameters

For gapless playback it is possible that each track can have different
codec profile with same decoder, for example we have WMA album,
we may have different tracks as WMA v9, WMA v10 and so on

Or if DSP's like QDSP have abililty to switch decoders on single stream
for each track, then this call could be used to set new codec parameters.

Existing code does not allow to change this profile while doing gapless
playback.

This patch adds new SNDRV_COMPRESS_SET_CODEC_PARAMS IOCTL to allow
userspace to set this new parameters required for new codec profile.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
---
 .../sound/designs/compress-offload.rst        |  6 ++++
 include/sound/compress_driver.h               |  5 +++
 include/uapi/sound/compress_offload.h         |  1 +
 sound/core/compress_offload.c                 | 34 +++++++++++++++++++
 4 files changed, 46 insertions(+)

diff --git a/Documentation/sound/designs/compress-offload.rst b/Documentation/sound/designs/compress-offload.rst
index 935f325dbc77..305ccc7bfdd9 100644
--- a/Documentation/sound/designs/compress-offload.rst
+++ b/Documentation/sound/designs/compress-offload.rst
@@ -128,6 +128,12 @@ set_params
   cases decoders will ignore other fields, while encoders will strictly
   comply to the settings
 
+set_codec_params
+  This routine is very much simillar to set_params but exculding stream
+  information. Only codec related information is set as part of this.
+  It is used in gapless playback where its required to change decoder
+  or its parameters for next track. This is optional.
+
 get_params
   This routines returns the actual settings used by the DSP. Changes to
   the settings should remain the exception.
diff --git a/include/sound/compress_driver.h b/include/sound/compress_driver.h
index 70cbc5095e72..d9c00bcfce9b 100644
--- a/include/sound/compress_driver.h
+++ b/include/sound/compress_driver.h
@@ -93,6 +93,9 @@ struct snd_compr_stream {
  * @set_params: Sets the compressed stream parameters, mandatory
  * This can be called in during stream creation only to set codec params
  * and the stream properties
+ * @set_codec_params: Sets the compressed stream codec parameters, Optional
+ * This can be called in during gapless next track codec change only to set
+ * codec params
  * @get_params: retrieve the codec parameters, mandatory
  * @set_metadata: Set the metadata values for a stream
  * @get_metadata: retrieves the requested metadata values from stream
@@ -112,6 +115,8 @@ struct snd_compr_ops {
 	int (*free)(struct snd_compr_stream *stream);
 	int (*set_params)(struct snd_compr_stream *stream,
 			struct snd_compr_params *params);
+	int (*set_codec_params)(struct snd_compr_stream *stream,
+			struct snd_codec *params);
 	int (*get_params)(struct snd_compr_stream *stream,
 			struct snd_codec *params);
 	int (*set_metadata)(struct snd_compr_stream *stream,
diff --git a/include/uapi/sound/compress_offload.h b/include/uapi/sound/compress_offload.h
index 7184265c0b0d..c46286113a4b 100644
--- a/include/uapi/sound/compress_offload.h
+++ b/include/uapi/sound/compress_offload.h
@@ -172,6 +172,7 @@ struct snd_compr_metadata {
 						 struct snd_compr_metadata)
 #define SNDRV_COMPRESS_GET_METADATA	_IOWR('C', 0x15,\
 						 struct snd_compr_metadata)
+#define SNDRV_COMPRESS_SET_CODEC_PARAMS	_IOW('C', 0x16, struct snd_codec)
 #define SNDRV_COMPRESS_TSTAMP		_IOR('C', 0x20, struct snd_compr_tstamp)
 #define SNDRV_COMPRESS_AVAIL		_IOR('C', 0x21, struct snd_compr_avail)
 #define SNDRV_COMPRESS_PAUSE		_IO('C', 0x30)
diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index af5824113246..184722643c97 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -590,6 +590,37 @@ static int snd_compress_check_input(struct snd_compr_params *params)
 
 }
 
+static int snd_compr_set_codec_params(struct snd_compr_stream *stream,
+				      unsigned long arg)
+{
+	struct snd_codec *params;
+	int retval;
+
+	if (!stream->ops->set_codec_params)
+		return -EPERM;
+
+	if (stream->runtime->state != SNDRV_PCM_STATE_RUNNING)
+		return -EPERM;
+
+	/* codec params can be only set when next track has been signalled */
+	if (stream->next_track == false)
+		return -EPERM;
+
+	params = memdup_user((void __user *)arg, sizeof(*params));
+	if (IS_ERR(params))
+		return PTR_ERR(params);
+
+	retval = snd_compress_check_codec_params(params);
+	if (retval)
+		goto out;
+
+	retval = stream->ops->set_codec_params(stream, params);
+
+out:
+	kfree(params);
+	return retval;
+}
+
 static int
 snd_compr_set_params(struct snd_compr_stream *stream, unsigned long arg)
 {
@@ -973,6 +1004,9 @@ static long snd_compr_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 	case _IOC_NR(SNDRV_COMPRESS_GET_PARAMS):
 		retval = snd_compr_get_params(stream, arg);
 		break;
+	case _IOC_NR(SNDRV_COMPRESS_SET_CODEC_PARAMS):
+		retval = snd_compr_set_codec_params(stream, arg);
+		break;
 	case _IOC_NR(SNDRV_COMPRESS_SET_METADATA):
 		retval = snd_compr_set_metadata(stream, arg);
 		break;
-- 
2.21.0