Thanks Takashi for review,

On 14/06/2023 08:04, Takashi Iwai wrote:

On Fri, 09 Jun 2023 17:04:16 +0200, Srinivas Kandagatla wrote:

...

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.

Reuse existing SNDRV_COMPRESS_SET_PARAMS to set this new track params along some additional checks to enforce proper state machine.

With this new changes now the user can call SNDRV_COMPRESS_SET_PARAMS anytime after setting next track and additional check in write should also ensure that params are set before writing new data.

Signed-off-by: Srinivas Kandagatla srinivas.kandagatla@linaro.org

Changes since v1/RFC:

• removed introduction of new IOCTL, as suggested.
• update the state-machine doc.

.../sound/designs/compress-offload.rst | 52 +++++++++---------- sound/core/compress_offload.c | 10 ++-- 2 files changed, 33 insertions(+), 29 deletions(-)

diff --git a/Documentation/sound/designs/compress-offload.rst b/Documentation/sound/designs/compress-offload.rst index 935f325dbc77..205cadcabe70 100644 --- a/Documentation/sound/designs/compress-offload.rst +++ b/Documentation/sound/designs/compress-offload.rst @@ -256,32 +256,32 @@ Gapless Playback SM For Gapless, we move from running state to partial drain and back, along with setting of meta_data and signalling for next track ::

•                                    +----------+
  

•            compr_drain_notify()    |          |
  

•          +------------------------>|  RUNNING |
  

•          |                         |          |
  

•          |                         +----------+
  

•          |                              |
  

•          |                              |
  

•          |                              | compr_next_track()
  

•          |                              |
  

•          |                              V
  

•          |                         +----------+
  

•          |                         |          |
  

•          |                         |NEXT_TRACK|
  

•          |                         |          |
  

•          |                         +----------+
  

•          |                              |
  

•          |                              |
  

•          |                              | compr_partial_drain()
  

•          |                              |
  

•          |                              V
  

•          |                         +----------+
  

•          |                         |          |
  

•          +------------------------ | PARTIAL_ |
  

•                                    |  DRAIN   |
  

•                                    +----------+
  

•                        +----------+
  

• compr_drain_notify()   |          | compr_set_params() iff next-track set.
  

• +------------------------>| RUNNING |----------------------+

• | | | |

• | +----------+ |

• | | |

• | | |

• | | compr_next_track() |

• | | V

• | V |

• | +----------+ |

• | | | |

• | |NEXT_TRACK| |

• | | | |

• | +----------+ |

• | | |

• | +----------------------------+

• | |

• | | compr_partial_drain()

• | |

• | V

• | +----------+

• | | |

• +------------------------ | PARTIAL_ |

•                        |  DRAIN   |
  

•                        +----------+
  
  

  Not supported

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c index 243acad89fd3..fe67228e74b3 100644 --- a/sound/core/compress_offload.c +++ b/sound/core/compress_offload.c @@ -294,6 +294,9 @@ static ssize_t snd_compr_write(struct file *f, const char __user *buf, case SNDRV_PCM_STATE_SETUP: case SNDRV_PCM_STATE_PREPARED: case SNDRV_PCM_STATE_RUNNING:

• /* Make sure next track params are set before writing new data */
  

• if (stream->next_track)
  

• 	return -EPERM;
  

Hm, does this logic correctly match with the comment above?

Yes I agree, it bit confusing and also going to break the partial drain path.

Also, this misses the mutex unlock.

Thinking about this again, Its not required have this check here to start with.

Something like below works, I can send this as v3, if this looks fine.

------------------------->cut<----------------------------------

diff --git a/Documentation/sound/designs/compress-offload.rst b/Documentation/sound/designs/compress-offload.rst index 935f325dbc77..655624f77092 100644 --- a/Documentation/sound/designs/compress-offload.rst +++ b/Documentation/sound/designs/compress-offload.rst @@ -268,11 +268,12 @@ with setting of meta_data and signalling for next track :: | | | V | +----------+ - | | | - | |NEXT_TRACK| - | | | - | +----------+ - | | + | compr_set_params() | | + | +-----------|NEXT_TRACK| + | | | | + | | +--+-------+ + | | | | + | +--------------+ | | | | | compr_partial_drain() | | diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c index 243acad89fd3..30f73097447b 100644 --- a/sound/core/compress_offload.c +++ b/sound/core/compress_offload.c @@ -589,7 +589,7 @@ snd_compr_set_params(struct snd_compr_stream *stream, unsigned long arg) struct snd_compr_params *params; int retval;

- if (stream->runtime->state == SNDRV_PCM_STATE_OPEN) { + if (stream->runtime->state == SNDRV_PCM_STATE_OPEN || stream->next_track) { /* * we should allow parameter change only when stream has been * opened not in other cases @@ -612,6 +612,9 @@ snd_compr_set_params(struct snd_compr_stream *stream, unsigned long arg) if (retval) goto out;

+ if (stream->next_track) + goto out; + stream->metadata_set = false; stream->next_track = false; ------------------------->cut<----------------------------------

thanks,

Takashi